Merge pull request #1437 from urfave/merging-main-to-v3-dev-main

Merging main to v3 dev main

.github/stale.yml

@@ -1,17 +0,0 @@
-# Number of days of inactivity before an issue becomes stale
-daysUntilStale: 365
-# Number of days of inactivity before a stale issue is closed
-daysUntilClose: 90
-# Issues with these labels will never be considered stale
-exemptLabels:
-  - pinned
-  - security
-# Label to use when marking an issue as stale
-staleLabel: wontfix
-# Comment to post when marking an issue as stale. Set to `false` to disable
-markComment: >
-  This issue has been automatically marked as stale because it has not had
-  recent activity. It will be closed if no further activity occurs. Thank you
-  for your contributions.
-# Comment to post when closing a stale issue. Set to `false` to disable
-closeComment: false

.github/workflows/cli.yml

@@ -34,20 +34,26 @@ jobs:
         uses: actions/checkout@v3
 
       - name: GOFMT Check
-        if: matrix.go == '1.17.x' && matrix.os == 'ubuntu-latest'
+        if: matrix.go == '1.18.x' && matrix.os == 'ubuntu-latest'
         run: test -z $(gofmt -l .)
 
       - name: vet
         run: go run internal/build/build.go vet
 
+      - name: test with urfave_cli_no_docs tag
+        run: go run internal/build/build.go -tags urfave_cli_no_docs test
+
       - name: test
         run: go run internal/build/build.go test
 
       - name: check-binary-size
         run: go run internal/build/build.go check-binary-size
 
+      - name: check-binary-size with tags (informational only)
+        run: go run internal/build/build.go -tags urfave_cli_no_docs check-binary-size
+
       - name: Upload coverage to Codecov
-        if: success() && matrix.go == '1.17.x' && matrix.os == 'ubuntu-latest'
+        if: success() && matrix.go == '1.18.x' && matrix.os == 'ubuntu-latest'
         uses: codecov/codecov-action@v2
         with:
           fail_ci_if_error: true
@@ -73,14 +79,37 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Install Dependencies
-        run:
+        run: |
-          mkdir -p "${GITHUB_WORKSPACE}/.local/bin" &&
+          mkdir -p "${GITHUB_WORKSPACE}/.local/bin"
-          curl -fsSL -o "${GITHUB_WORKSPACE}/.local/bin/gfmrun" "https://github.com/urfave/gfmrun/releases/download/v1.3.0/gfmrun-$(go env GOOS)-$(go env GOARCH)-v1.3.0" &&
+          curl -fsSL -o "${GITHUB_WORKSPACE}/.local/bin/gfmrun" "https://github.com/urfave/gfmrun/releases/download/v1.3.0/gfmrun-$(go env GOOS)-$(go env GOARCH)-v1.3.0"
-          chmod +x "${GITHUB_WORKSPACE}/.local/bin/gfmrun" &&
+          chmod +x "${GITHUB_WORKSPACE}/.local/bin/gfmrun"
-          npm install -g markdown-toc@1.2.0
 
       - name: gfmrun
         run: go run internal/build/build.go gfmrun docs/v2/manual.md
 
-      - name: toc
+      - name: diff check
-        run: go run internal/build/build.go toc docs/v2/manual.md
+        run: |
+          git diff --exit-code
+          git diff --cached --exit-code
+
+  publish:
+    if: startswith(github.ref, 'refs/tags/')
+    name: publish
+    needs: [test-docs]
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Code
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - name: Setup mkdocs
+        run: |
+          pip install -U pip
+          pip install -r mkdocs-requirements.txt
+          git remote rm origin
+          git remote add origin https://x-access-token:${{ secrets.GITHUB_TOKEN }}@github.com/urfave/cli.git
+
+      - name: Publish Docs
+        run: |
+          mkdocs gh-deploy --force

.gitignore

@@ -1,10 +1,10 @@
 *.coverprofile
 *.orig
-node_modules/
 vendor
 .idea
 internal/*/built-example
 coverage.txt
 /.local/
+/site/
 
 *.exe

CODE_OF_CONDUCT.md

@@ -55,11 +55,12 @@ further defined and clarified by project maintainers.
 ## Enforcement
 
 Instances of abusive, harassing, or otherwise unacceptable behavior may be
-reported by contacting Dan Buch at dan@meatballhat.com. All complaints will be
+reported by contacting urfave-governance@googlegroups.com, a members-only group
-reviewed and investigated and will result in a response that is deemed necessary
+that is world-postable. All complaints will be reviewed and investigated and
-and appropriate to the circumstances. The project team is obligated to maintain
+will result in a response that is deemed necessary and appropriate to the
-confidentiality with regard to the reporter of an incident.  Further details of
+circumstances. The project team is obligated to maintain confidentiality with
-specific enforcement policies may be posted separately.
+regard to the reporter of an incident. Further details of specific enforcement
+policies may be posted separately.
 
 Project maintainers who do not follow or enforce the Code of Conduct in good
 faith may face temporary or permanent repercussions as determined by other

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2016 Jeremy Saenz & Contributors
+Copyright (c) 2022 urfave/cli maintainers
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

Makefile

@@ -0,0 +1,40 @@
+# NOTE: this Makefile is meant to provide a simplified entry point for humans to
+# run all of the critical steps to verify one's changes are harmonious in
+# nature. Keeping target bodies to one line each and abstaining from make magic
+# are very important so that maintainers and contributors can focus their
+# attention on files that are primarily Go.
+
+.PHONY: all
+all: generate vet tag-test test check-binary-size tag-check-binary-size gfmrun v2diff
+
+# NOTE: this is a special catch-all rule to run any of the commands
+# defined in internal/build/build.go with optional arguments passed
+# via GFLAGS (global flags) and FLAGS (command-specific flags), e.g.:
+#
+#   $ make test GFLAGS='--packages cli'
+%:
+	go run internal/build/build.go $(GFLAGS) $* $(FLAGS)
+
+.PHONY: tag-test
+tag-test:
+	go run internal/build/build.go -tags urfave_cli_no_docs test
+
+.PHONY: tag-check-binary-size
+tag-check-binary-size:
+	go run internal/build/build.go -tags urfave_cli_no_docs check-binary-size
+
+.PHONY: gfmrun
+gfmrun:
+	go run internal/build/build.go gfmrun docs/v2/manual.md
+
+.PHONY: docs
+docs:
+	mkdocs build
+
+.PHONY: docs-deps
+docs-deps:
+	pip install -r mkdocs-requirements.txt
+
+.PHONY: serve-docs
+serve-docs:
+	mkdocs serve

README.md

@@ -1,5 +1,4 @@
-cli
+# cli
-===
 
 [![GoDoc](https://godoc.org/github.com/urfave/cli?status.svg)](https://pkg.go.dev/github.com/urfave/cli/v2)
 [![codebeat](https://codebeat.co/badges/0a8f30aa-f975-404b-b878-5fab3ae1cc5f)](https://codebeat.co/projects/github-com-urfave-cli)
@@ -10,61 +9,11 @@ cli is a simple, fast, and fun package for building command line apps in Go. The
 goal is to enable developers to write fast and distributable command line
 applications in an expressive way.
 
-## Usage Documentation
+## Documentation
 
-Usage documentation exists for each major version. Don't know what version you're on? You're probably using the version from the `main` branch, which is currently `v2`.
+More documentation is available in [`./docs`](./docs) or the hosted
+documentation site at <https://cli.urfave.org>.
 
-- `v2` - [./docs/v2/manual.md](./docs/v2/manual.md)
+## License
-- `v1` - [./docs/v1/manual.md](./docs/v1/manual.md)
 
-Guides for migrating to newer versions:
+See [`LICENSE`](./LICENSE)
-
-- `v1-to-v2` - [./docs/migrate-v1-to-v2.md](./docs/migrate-v1-to-v2.md)
-
-## Installation
-
-Using this package requires a working Go environment. [See the install instructions for Go](http://golang.org/doc/install.html).
-
-Go Modules are required when using this package. [See the go blog guide on using Go Modules](https://blog.golang.org/using-go-modules).
-
-### Using `v2` releases
-
-```
-$ go get github.com/urfave/cli/v2
-```
-
-```go
-...
-import (
-  "github.com/urfave/cli/v2" // imports as package "cli"
-)
-...
-```
-
-### Using `v1` releases
-
-```
-$ go get github.com/urfave/cli
-```
-
-```go
-...
-import (
-  "github.com/urfave/cli"
-)
-...
-```
-
-### GOPATH
-
-Make sure your `PATH` includes the `$GOPATH/bin` directory so your commands can
-be easily used:
-```
-export PATH=$PATH:$GOPATH/bin
-```
-
-### Supported platforms
-
-cli is tested against multiple versions of Go on Linux, and against the latest
-released version of Go on OS X and Windows. This project uses Github Actions for
-builds. To see our currently supported go versions and platforms, look at the [./.github/workflows/cli.yml](https://github.com/urfave/cli/blob/main/.github/workflows/cli.yml).

altsrc/flag.go

@@ -13,18 +13,18 @@ import (
 // allows a value to be set on the existing parsed flags.
 type FlagInputSourceExtension interface {
 	cli.Flag
-	ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error
+	ApplyInputSourceValue(cCtx *cli.Context, isc InputSourceContext) error
 }
 
 // ApplyInputSourceValues iterates over all provided flags and
 // executes ApplyInputSourceValue on flags implementing the
 // FlagInputSourceExtension interface to initialize these flags
 // to an alternate input source.
-func ApplyInputSourceValues(context *cli.Context, inputSourceContext InputSourceContext, flags []cli.Flag) error {
+func ApplyInputSourceValues(cCtx *cli.Context, inputSourceContext InputSourceContext, flags []cli.Flag) error {
 	for _, f := range flags {
 		inputSourceExtendedFlag, isType := f.(FlagInputSourceExtension)
 		if isType {
-			err := inputSourceExtendedFlag.ApplyInputSourceValue(context, inputSourceContext)
+			err := inputSourceExtendedFlag.ApplyInputSourceValue(cCtx, inputSourceContext)
 			if err != nil {
 				return err
 			}
@@ -38,42 +38,40 @@ func ApplyInputSourceValues(context *cli.Context, inputSourceContext InputSource
 // input source based on the func provided. If there is no error it will then apply the new input source to any flags
 // that are supported by the input source
 func InitInputSource(flags []cli.Flag, createInputSource func() (InputSourceContext, error)) cli.BeforeFunc {
-	return func(context *cli.Context) error {
+	return func(cCtx *cli.Context) error {
 		inputSource, err := createInputSource()
 		if err != nil {
 			return fmt.Errorf("Unable to create input source: inner error: \n'%v'", err.Error())
 		}
 
-		return ApplyInputSourceValues(context, inputSource, flags)
+		return ApplyInputSourceValues(cCtx, inputSource, flags)
 	}
 }
 
 // InitInputSourceWithContext is used to to setup an InputSourceContext on a cli.Command Before method. It will create a new
 // input source based on the func provided with potentially using existing cli.Context values to initialize itself. If there is
 // no error it will then apply the new input source to any flags that are supported by the input source
-func InitInputSourceWithContext(flags []cli.Flag, createInputSource func(context *cli.Context) (InputSourceContext, error)) cli.BeforeFunc {
+func InitInputSourceWithContext(flags []cli.Flag, createInputSource func(cCtx *cli.Context) (InputSourceContext, error)) cli.BeforeFunc {
-	return func(context *cli.Context) error {
+	return func(cCtx *cli.Context) error {
-		inputSource, err := createInputSource(context)
+		inputSource, err := createInputSource(cCtx)
 		if err != nil {
 			return fmt.Errorf("Unable to create input source with context: inner error: \n'%v'", err.Error())
 		}
 
-		return ApplyInputSourceValues(context, inputSource, flags)
+		return ApplyInputSourceValues(cCtx, inputSource, flags)
 	}
 }
 
 // ApplyInputSourceValue applies a generic value to the flagSet if required
-func (f *GenericFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+func (f *GenericFlag) ApplyInputSourceValue(cCtx *cli.Context, isc InputSourceContext) error {
-	if f.set != nil {
+	if f.set != nil && !cCtx.IsSet(f.Name) && !isEnvVarSet(f.EnvVars) && isc.isSet(f.GenericFlag.Name) {
-		if !context.IsSet(f.Name) && !isEnvVarSet(f.EnvVars) {
+		value, err := isc.Generic(f.GenericFlag.Name)
-			value, err := isc.Generic(f.GenericFlag.Name)
+		if err != nil {
-			if err != nil {
+			return err
-				return err
+		}
-			}
+		if value != nil {
-			if value != nil {
+			for _, name := range f.Names() {
-				for _, name := range f.Names() {
+				_ = f.set.Set(name, value.String())
-					_ = f.set.Set(name, value.String())
-				}
 			}
 		}
 	}
@@ -82,20 +80,18 @@ func (f *GenericFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourc
 }
 
 // ApplyInputSourceValue applies a StringSlice value to the flagSet if required
-func (f *StringSliceFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+func (f *StringSliceFlag) ApplyInputSourceValue(cCtx *cli.Context, isc InputSourceContext) error {
-	if f.set != nil {
+	if f.set != nil && !cCtx.IsSet(f.Name) && !isEnvVarSet(f.EnvVars) && isc.isSet(f.StringSliceFlag.Name) {
-		if !context.IsSet(f.Name) && !isEnvVarSet(f.EnvVars) {
+		value, err := isc.StringSlice(f.StringSliceFlag.Name)
-			value, err := isc.StringSlice(f.StringSliceFlag.Name)
+		if err != nil {
-			if err != nil {
+			return err
-				return err
+		}
-			}
+		if value != nil {
-			if value != nil {
+			var sliceValue cli.StringSlice = *(cli.NewStringSlice(value...))
-				var sliceValue cli.StringSlice = *(cli.NewStringSlice(value...))
+			for _, name := range f.Names() {
-				for _, name := range f.Names() {
+				underlyingFlag := f.set.Lookup(name)
-					underlyingFlag := f.set.Lookup(name)
+				if underlyingFlag != nil {
-					if underlyingFlag != nil {
+					underlyingFlag.Value = &sliceValue
-						underlyingFlag.Value = &sliceValue
-					}
 				}
 			}
 		}
@@ -104,20 +100,18 @@ func (f *StringSliceFlag) ApplyInputSourceValue(context *cli.Context, isc InputS
 }
 
 // ApplyInputSourceValue applies a IntSlice value if required
-func (f *IntSliceFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+func (f *IntSliceFlag) ApplyInputSourceValue(cCtx *cli.Context, isc InputSourceContext) error {
-	if f.set != nil {
+	if f.set != nil && !cCtx.IsSet(f.Name) && !isEnvVarSet(f.EnvVars) && isc.isSet(f.IntSliceFlag.Name) {
-		if !context.IsSet(f.Name) && !isEnvVarSet(f.EnvVars) {
+		value, err := isc.IntSlice(f.IntSliceFlag.Name)
-			value, err := isc.IntSlice(f.IntSliceFlag.Name)
+		if err != nil {
-			if err != nil {
+			return err
-				return err
+		}
-			}
+		if value != nil {
-			if value != nil {
+			var sliceValue cli.IntSlice = *(cli.NewIntSlice(value...))
-				var sliceValue cli.IntSlice = *(cli.NewIntSlice(value...))
+			for _, name := range f.Names() {
-				for _, name := range f.Names() {
+				underlyingFlag := f.set.Lookup(name)
-					underlyingFlag := f.set.Lookup(name)
+				if underlyingFlag != nil {
-					if underlyingFlag != nil {
+					underlyingFlag.Value = &sliceValue
-						underlyingFlag.Value = &sliceValue
-					}
 				}
 			}
 		}
@@ -126,17 +120,15 @@ func (f *IntSliceFlag) ApplyInputSourceValue(context *cli.Context, isc InputSour
 }
 
 // ApplyInputSourceValue applies a Bool value to the flagSet if required
-func (f *BoolFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+func (f *BoolFlag) ApplyInputSourceValue(cCtx *cli.Context, isc InputSourceContext) error {
-	if f.set != nil {
+	if f.set != nil && !cCtx.IsSet(f.Name) && !isEnvVarSet(f.EnvVars) && isc.isSet(f.BoolFlag.Name) {
-		if !context.IsSet(f.Name) && !isEnvVarSet(f.EnvVars) {
+		value, err := isc.Bool(f.BoolFlag.Name)
-			value, err := isc.Bool(f.BoolFlag.Name)
+		if err != nil {
-			if err != nil {
+			return err
-				return err
+		}
-			}
+		if value {
-			if value {
+			for _, name := range f.Names() {
-				for _, name := range f.Names() {
+				_ = f.set.Set(name, strconv.FormatBool(value))
-					_ = f.set.Set(name, strconv.FormatBool(value))
-				}
 			}
 		}
 	}
@@ -144,17 +136,15 @@ func (f *BoolFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceCo
 }
 
 // ApplyInputSourceValue applies a String value to the flagSet if required
-func (f *StringFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+func (f *StringFlag) ApplyInputSourceValue(cCtx *cli.Context, isc InputSourceContext) error {
-	if f.set != nil {
+	if f.set != nil && !(cCtx.IsSet(f.Name) || isEnvVarSet(f.EnvVars)) && isc.isSet(f.StringFlag.Name) {
-		if !(context.IsSet(f.Name) || isEnvVarSet(f.EnvVars)) {
+		value, err := isc.String(f.StringFlag.Name)
-			value, err := isc.String(f.StringFlag.Name)
+		if err != nil {
-			if err != nil {
+			return err
-				return err
+		}
-			}
+		if value != "" {
-			if value != "" {
+			for _, name := range f.Names() {
-				for _, name := range f.Names() {
+				_ = f.set.Set(name, value)
-					_ = f.set.Set(name, value)
-				}
 			}
 		}
 	}
@@ -162,27 +152,25 @@ func (f *StringFlag) ApplyInputSourceValue(context *cli.Context, isc InputSource
 }
 
 // ApplyInputSourceValue applies a Path value to the flagSet if required
-func (f *PathFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+func (f *PathFlag) ApplyInputSourceValue(cCtx *cli.Context, isc InputSourceContext) error {
-	if f.set != nil {
+	if f.set != nil && !(cCtx.IsSet(f.Name) || isEnvVarSet(f.EnvVars)) && isc.isSet(f.PathFlag.Name) {
-		if !(context.IsSet(f.Name) || isEnvVarSet(f.EnvVars)) {
+		value, err := isc.String(f.PathFlag.Name)
-			value, err := isc.String(f.PathFlag.Name)
+		if err != nil {
-			if err != nil {
+			return err
-				return err
+		}
-			}
+		if value != "" {
-			if value != "" {
+			for _, name := range f.Names() {
-				for _, name := range f.Names() {
 
-					if !filepath.IsAbs(value) && isc.Source() != "" {
+				if !filepath.IsAbs(value) && isc.Source() != "" {
-						basePathAbs, err := filepath.Abs(isc.Source())
+					basePathAbs, err := filepath.Abs(isc.Source())
-						if err != nil {
+					if err != nil {
-							return err
+						return err
-						}
-
-						value = filepath.Join(filepath.Dir(basePathAbs), value)
 					}
 
-					_ = f.set.Set(name, value)
+					value = filepath.Join(filepath.Dir(basePathAbs), value)
 				}
+
+				_ = f.set.Set(name, value)
 			}
 		}
 	}
@@ -190,55 +178,43 @@ func (f *PathFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceCo
 }
 
 // ApplyInputSourceValue applies a int value to the flagSet if required
-func (f *IntFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+func (f *IntFlag) ApplyInputSourceValue(cCtx *cli.Context, isc InputSourceContext) error {
-	if f.set != nil {
+	if f.set != nil && !(cCtx.IsSet(f.Name) || isEnvVarSet(f.EnvVars)) && isc.isSet(f.IntFlag.Name) {
-		if !(context.IsSet(f.Name) || isEnvVarSet(f.EnvVars)) {
+		value, err := isc.Int(f.IntFlag.Name)
-			value, err := isc.Int(f.IntFlag.Name)
+		if err != nil {
-			if err != nil {
+			return err
-				return err
+		}
-			}
+		for _, name := range f.Names() {
-			if value > 0 {
+			_ = f.set.Set(name, strconv.FormatInt(int64(value), 10))
-				for _, name := range f.Names() {
-					_ = f.set.Set(name, strconv.FormatInt(int64(value), 10))
-				}
-			}
 		}
 	}
 	return nil
 }
 
 // ApplyInputSourceValue applies a Duration value to the flagSet if required
-func (f *DurationFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+func (f *DurationFlag) ApplyInputSourceValue(cCtx *cli.Context, isc InputSourceContext) error {
-	if f.set != nil {
+	if f.set != nil && !(cCtx.IsSet(f.Name) || isEnvVarSet(f.EnvVars)) && isc.isSet(f.DurationFlag.Name) {
-		if !(context.IsSet(f.Name) || isEnvVarSet(f.EnvVars)) {
+		value, err := isc.Duration(f.DurationFlag.Name)
-			value, err := isc.Duration(f.DurationFlag.Name)
+		if err != nil {
-			if err != nil {
+			return err
-				return err
+		}
-			}
+		for _, name := range f.Names() {
-			if value > 0 {
+			_ = f.set.Set(name, value.String())
-				for _, name := range f.Names() {
-					_ = f.set.Set(name, value.String())
-				}
-			}
 		}
 	}
 	return nil
 }
 
 // ApplyInputSourceValue applies a Float64 value to the flagSet if required
-func (f *Float64Flag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+func (f *Float64Flag) ApplyInputSourceValue(cCtx *cli.Context, isc InputSourceContext) error {
-	if f.set != nil {
+	if f.set != nil && !(cCtx.IsSet(f.Name) || isEnvVarSet(f.EnvVars)) && isc.isSet(f.Float64Flag.Name) {
-		if !(context.IsSet(f.Name) || isEnvVarSet(f.EnvVars)) {
+		value, err := isc.Float64(f.Float64Flag.Name)
-			value, err := isc.Float64(f.Float64Flag.Name)
+		if err != nil {
-			if err != nil {
+			return err
-				return err
+		}
-			}
+		floatStr := float64ToString(value)
-			if value > 0 {
+		for _, name := range f.Names() {
-				floatStr := float64ToString(value)
+			_ = f.set.Set(name, floatStr)
-				for _, name := range f.Names() {
-					_ = f.set.Set(name, floatStr)
-				}
-			}
 		}
 	}
 	return nil

altsrc/flag_test.go

@@ -26,29 +26,48 @@ type testApplyInputSource struct {
 	MapValue           interface{}
 }
 
+type racyInputSource struct {
+	*MapInputSource
+}
+
+func (ris *racyInputSource) isSet(name string) bool {
+	if _, ok := ris.MapInputSource.valueMap[name]; ok {
+		ris.MapInputSource.valueMap[name] = bogus{0}
+	}
+	return true
+}
+
 func TestGenericApplyInputSourceValue(t *testing.T) {
 	v := &Parser{"abc", "def"}
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:     NewGenericFlag(&cli.GenericFlag{Name: "test", Value: &Parser{}}),
 		FlagName: "test",
 		MapValue: v,
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, v, c.Generic("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, v, c.Generic("test"))
 }
 
 func TestGenericApplyInputSourceMethodContextSet(t *testing.T) {
 	p := &Parser{"abc", "def"}
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:               NewGenericFlag(&cli.GenericFlag{Name: "test", Value: &Parser{}}),
 		FlagName:           "test",
 		MapValue:           &Parser{"efg", "hig"},
 		ContextValueString: p.String(),
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, p, c.Generic("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, p, c.Generic("test"))
 }
 
 func TestGenericApplyInputSourceMethodEnvVarSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag: NewGenericFlag(&cli.GenericFlag{
 			Name:    "test",
 			Value:   &Parser{},
@@ -58,17 +77,25 @@ func TestGenericApplyInputSourceMethodEnvVarSet(t *testing.T) {
 		MapValue:    &Parser{"efg", "hij"},
 		EnvVarName:  "TEST",
 		EnvVarValue: "abc,def",
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, &Parser{"abc", "def"}, c.Generic("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, &Parser{"abc", "def"}, c.Generic("test"))
 }
 
 func TestStringSliceApplyInputSourceValue(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:     NewStringSliceFlag(&cli.StringSliceFlag{Name: "test"}),
 		FlagName: "test",
 		MapValue: []interface{}{"hello", "world"},
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, c.StringSlice("test"), []string{"hello", "world"})
+
+	c = runRacyTest(t, tis)
+	refute(t, c.StringSlice("test"), []string{"hello", "world"})
 }
 
 func TestStringSliceApplyInputSourceMethodContextSet(t *testing.T) {
@@ -82,112 +109,154 @@ func TestStringSliceApplyInputSourceMethodContextSet(t *testing.T) {
 }
 
 func TestStringSliceApplyInputSourceMethodEnvVarSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:        NewStringSliceFlag(&cli.StringSliceFlag{Name: "test", EnvVars: []string{"TEST"}}),
 		FlagName:    "test",
 		MapValue:    []interface{}{"hello", "world"},
 		EnvVarName:  "TEST",
 		EnvVarValue: "oh,no",
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, c.StringSlice("test"), []string{"oh", "no"})
+
+	c = runRacyTest(t, tis)
+	refute(t, c.StringSlice("test"), []string{"oh", "no"})
 }
 
 func TestIntSliceApplyInputSourceValue(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:     NewIntSliceFlag(&cli.IntSliceFlag{Name: "test"}),
 		FlagName: "test",
 		MapValue: []interface{}{1, 2},
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, c.IntSlice("test"), []int{1, 2})
+
+	c = runRacyTest(t, tis)
+	refute(t, c.IntSlice("test"), []int{1, 2})
 }
 
 func TestIntSliceApplyInputSourceMethodContextSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:               NewIntSliceFlag(&cli.IntSliceFlag{Name: "test"}),
 		FlagName:           "test",
 		MapValue:           []interface{}{1, 2},
 		ContextValueString: "3",
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, c.IntSlice("test"), []int{3})
+
+	c = runRacyTest(t, tis)
+	refute(t, c.IntSlice("test"), []int{3})
 }
 
 func TestIntSliceApplyInputSourceMethodEnvVarSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:        NewIntSliceFlag(&cli.IntSliceFlag{Name: "test", EnvVars: []string{"TEST"}}),
 		FlagName:    "test",
 		MapValue:    []interface{}{1, 2},
 		EnvVarName:  "TEST",
 		EnvVarValue: "3,4",
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, c.IntSlice("test"), []int{3, 4})
+
+	c = runRacyTest(t, tis)
+	refute(t, c.IntSlice("test"), []int{3, 4})
 }
 
 func TestBoolApplyInputSourceMethodSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:     NewBoolFlag(&cli.BoolFlag{Name: "test"}),
 		FlagName: "test",
 		MapValue: true,
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, true, c.Bool("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, true, c.Bool("test"))
 }
 
 func TestBoolApplyInputSourceMethodContextSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:               NewBoolFlag(&cli.BoolFlag{Name: "test"}),
 		FlagName:           "test",
 		MapValue:           false,
 		ContextValueString: "true",
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, true, c.Bool("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, true, c.Bool("test"))
 }
 
 func TestBoolApplyInputSourceMethodEnvVarSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:        NewBoolFlag(&cli.BoolFlag{Name: "test", EnvVars: []string{"TEST"}}),
 		FlagName:    "test",
 		MapValue:    false,
 		EnvVarName:  "TEST",
 		EnvVarValue: "true",
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, true, c.Bool("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, true, c.Bool("test"))
 }
 
 func TestStringApplyInputSourceMethodSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:     NewStringFlag(&cli.StringFlag{Name: "test"}),
 		FlagName: "test",
 		MapValue: "hello",
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, "hello", c.String("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, "hello", c.String("test"))
 }
 
 func TestStringApplyInputSourceMethodContextSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:               NewStringFlag(&cli.StringFlag{Name: "test"}),
 		FlagName:           "test",
 		MapValue:           "hello",
 		ContextValueString: "goodbye",
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, "goodbye", c.String("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, "goodbye", c.String("test"))
 }
 
 func TestStringApplyInputSourceMethodEnvVarSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:        NewStringFlag(&cli.StringFlag{Name: "test", EnvVars: []string{"TEST"}}),
 		FlagName:    "test",
 		MapValue:    "hello",
 		EnvVarName:  "TEST",
 		EnvVarValue: "goodbye",
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, "goodbye", c.String("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, "goodbye", c.String("test"))
 }
+
 func TestPathApplyInputSourceMethodSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:       NewPathFlag(&cli.PathFlag{Name: "test"}),
 		FlagName:   "test",
 		MapValue:   "hello",
 		SourcePath: "/path/to/source/file",
-	})
+	}
+	c := runTest(t, tis)
 
 	expected := "/path/to/source/hello"
 	if runtime.GOOS == "windows" {
@@ -200,119 +269,214 @@ func TestPathApplyInputSourceMethodSet(t *testing.T) {
 		}
 	}
 	expect(t, expected, c.String("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, expected, c.String("test"))
 }
 
 func TestPathApplyInputSourceMethodContextSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:               NewPathFlag(&cli.PathFlag{Name: "test"}),
 		FlagName:           "test",
 		MapValue:           "hello",
 		ContextValueString: "goodbye",
 		SourcePath:         "/path/to/source/file",
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, "goodbye", c.String("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, "goodbye", c.String("test"))
 }
 
 func TestPathApplyInputSourceMethodEnvVarSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:        NewPathFlag(&cli.PathFlag{Name: "test", EnvVars: []string{"TEST"}}),
 		FlagName:    "test",
 		MapValue:    "hello",
 		EnvVarName:  "TEST",
 		EnvVarValue: "goodbye",
 		SourcePath:  "/path/to/source/file",
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, "goodbye", c.String("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, "goodbye", c.String("test"))
 }
 
 func TestIntApplyInputSourceMethodSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:     NewIntFlag(&cli.IntFlag{Name: "test"}),
 		FlagName: "test",
 		MapValue: 15,
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, 15, c.Int("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, 15, c.Int("test"))
+}
+
+func TestIntApplyInputSourceMethodSetNegativeValue(t *testing.T) {
+	tis := testApplyInputSource{
+		Flag:     NewIntFlag(&cli.IntFlag{Name: "test"}),
+		FlagName: "test",
+		MapValue: -1,
+	}
+	c := runTest(t, tis)
+	expect(t, -1, c.Int("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, -1, c.Int("test"))
 }
 
 func TestIntApplyInputSourceMethodContextSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:               NewIntFlag(&cli.IntFlag{Name: "test"}),
 		FlagName:           "test",
 		MapValue:           15,
 		ContextValueString: "7",
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, 7, c.Int("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, 7, c.Int("test"))
 }
 
 func TestIntApplyInputSourceMethodEnvVarSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:        NewIntFlag(&cli.IntFlag{Name: "test", EnvVars: []string{"TEST"}}),
 		FlagName:    "test",
 		MapValue:    15,
 		EnvVarName:  "TEST",
 		EnvVarValue: "12",
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, 12, c.Int("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, 12, c.Int("test"))
 }
 
 func TestDurationApplyInputSourceMethodSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:     NewDurationFlag(&cli.DurationFlag{Name: "test"}),
 		FlagName: "test",
 		MapValue: 30 * time.Second,
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, 30*time.Second, c.Duration("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, 30*time.Second, c.Duration("test"))
+}
+
+func TestDurationApplyInputSourceMethodSetNegativeValue(t *testing.T) {
+	tis := testApplyInputSource{
+		Flag:     NewDurationFlag(&cli.DurationFlag{Name: "test"}),
+		FlagName: "test",
+		MapValue: -30 * time.Second,
+	}
+	c := runTest(t, tis)
+	expect(t, -30*time.Second, c.Duration("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, -30*time.Second, c.Duration("test"))
 }
 
 func TestDurationApplyInputSourceMethodContextSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:               NewDurationFlag(&cli.DurationFlag{Name: "test"}),
 		FlagName:           "test",
 		MapValue:           30 * time.Second,
 		ContextValueString: (15 * time.Second).String(),
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, 15*time.Second, c.Duration("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, 15*time.Second, c.Duration("test"))
 }
 
 func TestDurationApplyInputSourceMethodEnvVarSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:        NewDurationFlag(&cli.DurationFlag{Name: "test", EnvVars: []string{"TEST"}}),
 		FlagName:    "test",
 		MapValue:    30 * time.Second,
 		EnvVarName:  "TEST",
 		EnvVarValue: (15 * time.Second).String(),
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, 15*time.Second, c.Duration("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, 15*time.Second, c.Duration("test"))
 }
 
 func TestFloat64ApplyInputSourceMethodSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:     NewFloat64Flag(&cli.Float64Flag{Name: "test"}),
 		FlagName: "test",
 		MapValue: 1.3,
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, 1.3, c.Float64("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, 1.3, c.Float64("test"))
+}
+
+func TestFloat64ApplyInputSourceMethodSetNegativeValue(t *testing.T) {
+	tis := testApplyInputSource{
+		Flag:     NewFloat64Flag(&cli.Float64Flag{Name: "test"}),
+		FlagName: "test",
+		MapValue: -1.3,
+	}
+	c := runTest(t, tis)
+	expect(t, -1.3, c.Float64("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, -1.3, c.Float64("test"))
+}
+
+func TestFloat64ApplyInputSourceMethodSetNegativeValueNotSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:     NewFloat64Flag(&cli.Float64Flag{Name: "test1"}),
+		FlagName: "test1",
+		// dont set map value
+	})
+	expect(t, 0.0, c.Float64("test1"))
 }
 
 func TestFloat64ApplyInputSourceMethodContextSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:               NewFloat64Flag(&cli.Float64Flag{Name: "test"}),
 		FlagName:           "test",
 		MapValue:           1.3,
 		ContextValueString: fmt.Sprintf("%v", 1.4),
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, 1.4, c.Float64("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, 1.4, c.Float64("test"))
 }
 
 func TestFloat64ApplyInputSourceMethodEnvVarSet(t *testing.T) {
-	c := runTest(t, testApplyInputSource{
+	tis := testApplyInputSource{
 		Flag:        NewFloat64Flag(&cli.Float64Flag{Name: "test", EnvVars: []string{"TEST"}}),
 		FlagName:    "test",
 		MapValue:    1.3,
 		EnvVarName:  "TEST",
 		EnvVarValue: fmt.Sprintf("%v", 1.4),
-	})
+	}
+	c := runTest(t, tis)
 	expect(t, 1.4, c.Float64("test"))
+
+	c = runRacyTest(t, tis)
+	refute(t, 1.4, c.Float64("test"))
 }
 
 func runTest(t *testing.T, test testApplyInputSource) *cli.Context {
@@ -340,6 +504,19 @@ func runTest(t *testing.T, test testApplyInputSource) *cli.Context {
 	return c
 }
 
+func runRacyTest(t *testing.T, test testApplyInputSource) *cli.Context {
+	set := flag.NewFlagSet(test.FlagSetName, flag.ContinueOnError)
+	c := cli.NewContext(nil, set, nil)
+	_ = test.Flag.ApplyInputSourceValue(c, &racyInputSource{
+		MapInputSource: &MapInputSource{
+			file:     test.SourcePath,
+			valueMap: map[interface{}]interface{}{test.FlagName: test.MapValue},
+		},
+	})
+
+	return c
+}
+
 type Parser [2]string
 
 func (p *Parser) Set(value string) error {
@@ -357,3 +534,5 @@ func (p *Parser) Set(value string) error {
 func (p *Parser) String() string {
 	return fmt.Sprintf("%s,%s", p[0], p[1])
 }
+
+type bogus [1]uint

altsrc/helpers_test.go

@@ -22,7 +22,10 @@ func expect(t *testing.T, a interface{}, b interface{}) {
 }
 
 func refute(t *testing.T, a interface{}, b interface{}) {
-	if a == b {
+	_, fn, line, _ := runtime.Caller(1)
-		t.Errorf("Did not expect %v (type %v) - Got %v (type %v)", b, reflect.TypeOf(b), a, reflect.TypeOf(a))
+	fn = strings.Replace(fn, wd+"/", "", -1)
+
+	if reflect.DeepEqual(a, b) {
+		t.Errorf("(%s:%d) Did not expect %v (type %v) - Got %v (type %v)", fn, line, b, reflect.TypeOf(b), a, reflect.TypeOf(a))
 	}
 }

altsrc/input_source_context.go

@@ -22,4 +22,6 @@ type InputSourceContext interface {
 	IntSlice(name string) ([]int, error)
 	Generic(name string) (cli.Generic, error)
 	Bool(name string) (bool, error)
+
+	isSet(name string) bool
 }

altsrc/json_source_context.go

@@ -16,9 +16,9 @@ import (
 // variables from a file containing JSON data with the file name defined
 // by the given flag.
 func NewJSONSourceFromFlagFunc(flag string) func(c *cli.Context) (InputSourceContext, error) {
-	return func(context *cli.Context) (InputSourceContext, error) {
+	return func(cCtx *cli.Context) (InputSourceContext, error) {
-		if context.IsSet(flag) {
+		if cCtx.IsSet(flag) {
-			return NewJSONSourceFromFile(context.String(flag))
+			return NewJSONSourceFromFile(cCtx.String(flag))
 		}
 
 		return defaultInputSource()
@@ -184,6 +184,11 @@ func (x *jsonSource) Bool(name string) (bool, error) {
 	return v, nil
 }
 
+func (x *jsonSource) isSet(name string) bool {
+	_, err := x.getValue(name)
+	return err == nil
+}
+
 func (x *jsonSource) getValue(key string) (interface{}, error) {
 	return jsonGetValue(key, x.deserialized)
 }

altsrc/map_input_source.go

@@ -32,11 +32,18 @@ func nestedVal(name string, tree map[interface{}]interface{}) (interface{}, bool
 			if !ok {
 				return nil, false
 			}
-			ctype, ok := child.(map[interface{}]interface{})
+
-			if !ok {
+			switch child := child.(type) {
+			case map[string]interface{}:
+				node = make(map[interface{}]interface{}, len(child))
+				for k, v := range child {
+					node[k] = v
+				}
+			case map[interface{}]interface{}:
+				node = child
+			default:
 				return nil, false
 			}
-			node = ctype
 		}
 		if val, ok := node[sections[len(sections)-1]]; ok {
 			return val, true
@@ -244,6 +251,15 @@ func (fsm *MapInputSource) Bool(name string) (bool, error) {
 	return false, nil
 }
 
+func (fsm *MapInputSource) isSet(name string) bool {
+	if _, exists := fsm.valueMap[name]; exists {
+		return exists
+	}
+
+	_, exists := nestedVal(name, fsm.valueMap)
+	return exists
+}
+
 func incorrectTypeForFlagError(name, expectedTypeName string, value interface{}) error {
 	valueType := reflect.TypeOf(value)
 	valueTypeName := ""

altsrc/toml_file_loader.go

@@ -85,10 +85,10 @@ func NewTomlSourceFromFile(file string) (InputSourceContext, error) {
 }
 
 // NewTomlSourceFromFlagFunc creates a new TOML InputSourceContext from a provided flag name and source context.
-func NewTomlSourceFromFlagFunc(flagFileName string) func(context *cli.Context) (InputSourceContext, error) {
+func NewTomlSourceFromFlagFunc(flagFileName string) func(cCtx *cli.Context) (InputSourceContext, error) {
-	return func(context *cli.Context) (InputSourceContext, error) {
+	return func(cCtx *cli.Context) (InputSourceContext, error) {
-		if context.IsSet(flagFileName) {
+		if cCtx.IsSet(flagFileName) {
-			filePath := context.String(flagFileName)
+			filePath := cCtx.String(flagFileName)
 			return NewTomlSourceFromFile(filePath)
 		}
 

altsrc/yaml_file_loader.go

@@ -11,7 +11,7 @@ import (
 
 	"github.com/urfave/cli/v2"
 
-	"gopkg.in/yaml.v2"
+	"gopkg.in/yaml.v3"
 )
 
 type yamlSourceContext struct {
@@ -31,10 +31,10 @@ func NewYamlSourceFromFile(file string) (InputSourceContext, error) {
 }
 
 // NewYamlSourceFromFlagFunc creates a new Yaml InputSourceContext from a provided flag name and source context.
-func NewYamlSourceFromFlagFunc(flagFileName string) func(context *cli.Context) (InputSourceContext, error) {
+func NewYamlSourceFromFlagFunc(flagFileName string) func(cCtx *cli.Context) (InputSourceContext, error) {
-	return func(context *cli.Context) (InputSourceContext, error) {
+	return func(cCtx *cli.Context) (InputSourceContext, error) {
-		if context.IsSet(flagFileName) {
+		if cCtx.IsSet(flagFileName) {
-			filePath := context.String(flagFileName)
+			filePath := cCtx.String(flagFileName)
 			return NewYamlSourceFromFile(filePath)
 		}
 

altsrc/yaml_file_loader_test.go

@@ -0,0 +1,87 @@
+package altsrc_test
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	"github.com/urfave/cli/v2"
+	"github.com/urfave/cli/v2/altsrc"
+)
+
+func ExampleApp_Run_yamlFileLoaderDuration() {
+	execServe := func(c *cli.Context) error {
+		keepaliveInterval := c.Duration("keepalive-interval")
+		fmt.Printf("keepalive %s\n", keepaliveInterval)
+		return nil
+	}
+
+	fileExists := func(filename string) bool {
+		stat, _ := os.Stat(filename)
+		return stat != nil
+	}
+
+	// initConfigFileInputSource is like altsrc.InitInputSourceWithContext and altsrc.NewYamlSourceFromFlagFunc, but checks
+	// if the config flag is exists and only loads it if it does. If the flag is set and the file exists, it fails.
+	initConfigFileInputSource := func(configFlag string, flags []cli.Flag) cli.BeforeFunc {
+		return func(context *cli.Context) error {
+			configFile := context.String(configFlag)
+			if context.IsSet(configFlag) && !fileExists(configFile) {
+				return fmt.Errorf("config file %s does not exist", configFile)
+			} else if !context.IsSet(configFlag) && !fileExists(configFile) {
+				return nil
+			}
+			inputSource, err := altsrc.NewYamlSourceFromFile(configFile)
+			if err != nil {
+				return err
+			}
+			return altsrc.ApplyInputSourceValues(context, inputSource, flags)
+		}
+	}
+
+	flagsServe := []cli.Flag{
+		&cli.StringFlag{
+			Name:        "config",
+			Aliases:     []string{"c"},
+			EnvVars:     []string{"CONFIG_FILE"},
+			Value:       "../testdata/empty.yml",
+			DefaultText: "../testdata/empty.yml",
+			Usage:       "config file",
+		},
+		altsrc.NewDurationFlag(
+			&cli.DurationFlag{
+				Name:    "keepalive-interval",
+				Aliases: []string{"k"},
+				EnvVars: []string{"KEEPALIVE_INTERVAL"},
+				Value:   45 * time.Second,
+				Usage:   "interval of keepalive messages",
+			},
+		),
+	}
+
+	cmdServe := &cli.Command{
+		Name:      "serve",
+		Usage:     "Run the server",
+		UsageText: "serve [OPTIONS..]",
+		Action:    execServe,
+		Flags:     flagsServe,
+		Before:    initConfigFileInputSource("config", flagsServe),
+	}
+
+	c := &cli.App{
+		Name:                   "cmd",
+		HideVersion:            true,
+		UseShortOptionHandling: true,
+		Commands: []*cli.Command{
+			cmdServe,
+		},
+	}
+
+	if err := c.Run([]string{"cmd", "serve", "--config", "../testdata/empty.yml"}); err != nil {
+		log.Fatal(err)
+	}
+
+	// Output:
+	// keepalive 45s
+}

app.go

@@ -7,10 +7,13 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"reflect"
 	"sort"
 	"time"
 )
 
+const suggestDidYouMeanTemplate = "Did you mean %q?"
+
 var (
 	changeLogURL            = "https://github.com/urfave/cli/blob/main/docs/CHANGELOG.md"
 	appActionDeprecationURL = fmt.Sprintf("%s#deprecated-cli-app-action-signature", changeLogURL)
@@ -18,6 +21,10 @@ var (
 	errInvalidActionType    = NewExitError("ERROR invalid Action type. "+
 		fmt.Sprintf("Must be `func(*Context`)` or `func(*Context) error).  %s", contactSysadmin)+
 		fmt.Sprintf("See %s", appActionDeprecationURL), 2)
+
+	SuggestFlag               SuggestFlagFunc    = suggestFlag
+	SuggestCommand            SuggestCommandFunc = suggestCommand
+	SuggestDidYouMeanTemplate string             = suggestDidYouMeanTemplate
 )
 
 // App is the main structure of a cli application. It is recommended that
@@ -37,6 +44,9 @@ type App struct {
 	Version string
 	// Description of the program
 	Description string
+	// DefaultCommand is the (optional) name of a command
+	// to run if no command names are passed as CLI arguments.
+	DefaultCommand string
 	// List of commands to execute
 	Commands []*Command
 	// List of flags to parse
@@ -52,6 +62,8 @@ type App struct {
 	HideVersion bool
 	// categories contains the categorized commands and is populated on app startup
 	categories CommandCategories
+	// flagCategories contains the categorized flags and is populated on app startup
+	flagCategories FlagCategories
 	// An action to execute when the shell completion flag is set
 	BashComplete BashCompleteFunc
 	// An action to execute before any subcommands are run, but after the context is ready
@@ -94,10 +106,16 @@ type App struct {
 	// single-character bool arguments into one
 	// i.e. foobar -o -v -> foobar -ov
 	UseShortOptionHandling bool
+	// Enable suggestions for commands and flags
+	Suggest bool
 
 	didSetup bool
 }
 
+type SuggestFlagFunc func(flags []Flag, provided string, hideHelp bool) string
+
+type SuggestCommandFunc func(commands []*Command, provided string) string
+
 // Tries to find out when this binary was compiled.
 // Returns the current time if it fails to find it.
 func compileTime() time.Time {
@@ -181,6 +199,8 @@ func (a *App) Setup() {
 		if c.HelpName == "" {
 			c.HelpName = fmt.Sprintf("%s %s", a.HelpName, c.Name)
 		}
+
+		c.flagCategories = newFlagCategoriesFromFlags(c.Flags)
 		newCommands = append(newCommands, c)
 	}
 	a.Commands = newCommands
@@ -205,6 +225,13 @@ func (a *App) Setup() {
 	}
 	sort.Sort(a.categories.(*commandCategories))
 
+	a.flagCategories = newFlagCategories()
+	for _, fl := range a.Flags {
+		if cf, ok := fl.(CategorizableFlag); ok {
+			a.flagCategories.AddFlag(cf.GetCategory(), cf)
+		}
+	}
+
 	if a.Metadata == nil {
 		a.Metadata = make(map[string]interface{})
 	}
@@ -245,48 +272,53 @@ func (a *App) RunContext(ctx context.Context, arguments []string) (err error) {
 
 	err = parseIter(set, a, arguments[1:], shellComplete)
 	nerr := normalizeFlags(a.Flags, set)
-	context := NewContext(a, set, &Context{Context: ctx})
+	cCtx := NewContext(a, set, &Context{Context: ctx})
 	if nerr != nil {
 		_, _ = fmt.Fprintln(a.Writer, nerr)
-		_ = ShowAppHelp(context)
+		_ = ShowAppHelp(cCtx)
 		return nerr
 	}
-	context.shellComplete = shellComplete
+	cCtx.shellComplete = shellComplete
 
-	if checkCompletions(context) {
+	if checkCompletions(cCtx) {
 		return nil
 	}
 
 	if err != nil {
 		if a.OnUsageError != nil {
-			err := a.OnUsageError(context, err, false)
+			err := a.OnUsageError(cCtx, err, false)
-			a.handleExitCoder(context, err)
+			a.handleExitCoder(cCtx, err)
 			return err
 		}
 		_, _ = fmt.Fprintf(a.Writer, "%s %s\n\n", "Incorrect Usage.", err.Error())
-		_ = ShowAppHelp(context)
+		if a.Suggest {
+			if suggestion, err := a.suggestFlagFromError(err, ""); err == nil {
+				fmt.Fprintf(a.Writer, suggestion)
+			}
+		}
+		_ = ShowAppHelp(cCtx)
 		return err
 	}
 
-	if !a.HideHelp && checkHelp(context) {
+	if !a.HideHelp && checkHelp(cCtx) {
-		_ = ShowAppHelp(context)
+		_ = ShowAppHelp(cCtx)
 		return nil
 	}
 
-	if !a.HideVersion && checkVersion(context) {
+	if !a.HideVersion && checkVersion(cCtx) {
-		ShowVersion(context)
+		ShowVersion(cCtx)
 		return nil
 	}
 
-	cerr := context.checkRequiredFlags(a.Flags)
+	cerr := cCtx.checkRequiredFlags(a.Flags)
 	if cerr != nil {
-		_ = ShowAppHelp(context)
+		_ = ShowAppHelp(cCtx)
 		return cerr
 	}
 
 	if a.After != nil {
 		defer func() {
-			if afterErr := a.After(context); afterErr != nil {
+			if afterErr := a.After(cCtx); afterErr != nil {
 				if err != nil {
 					err = newMultiError(err, afterErr)
 				} else {
@@ -297,21 +329,53 @@ func (a *App) RunContext(ctx context.Context, arguments []string) (err error) {
 	}
 
 	if a.Before != nil {
-		beforeErr := a.Before(context)
+		beforeErr := a.Before(cCtx)
 		if beforeErr != nil {
-			a.handleExitCoder(context, beforeErr)
+			a.handleExitCoder(cCtx, beforeErr)
 			err = beforeErr
 			return err
 		}
 	}
 
-	args := context.Args()
+	var c *Command
+	args := cCtx.Args()
 	if args.Present() {
 		name := args.First()
-		c := a.Command(name)
+		if a.validCommandName(name) {
-		if c != nil {
+			c = a.Command(name)
-			return c.Run(context)
+		} else {
+			hasDefault := a.DefaultCommand != ""
+			isFlagName := checkStringSliceIncludes(name, cCtx.FlagNames())
+
+			var (
+				isDefaultSubcommand   = false
+				defaultHasSubcommands = false
+			)
+
+			if hasDefault {
+				dc := a.Command(a.DefaultCommand)
+				defaultHasSubcommands = len(dc.Subcommands) > 0
+				for _, dcSub := range dc.Subcommands {
+					if checkStringSliceIncludes(name, dcSub.Names()) {
+						isDefaultSubcommand = true
+						break
+					}
+				}
+			}
+
+			if isFlagName || (hasDefault && (defaultHasSubcommands && isDefaultSubcommand)) {
+				argsWithDefault := a.argsWithDefaultCommand(args)
+				if !reflect.DeepEqual(args, argsWithDefault) {
+					c = a.Command(argsWithDefault.First())
+				}
+			}
 		}
+	} else if a.DefaultCommand != "" {
+		c = a.Command(a.DefaultCommand)
+	}
+
+	if c != nil {
+		return c.Run(cCtx)
 	}
 
 	if a.Action == nil {
@@ -319,12 +383,35 @@ func (a *App) RunContext(ctx context.Context, arguments []string) (err error) {
 	}
 
 	// Run default Action
-	err = a.Action(context)
+	err = a.Action(cCtx)
 
-	a.handleExitCoder(context, err)
+	a.handleExitCoder(cCtx, err)
 	return err
 }
 
+func (a *App) suggestFlagFromError(err error, command string) (string, error) {
+	flag, parseErr := flagFromError(err)
+	if parseErr != nil {
+		return "", err
+	}
+
+	flags := a.Flags
+	if command != "" {
+		cmd := a.Command(command)
+		if cmd == nil {
+			return "", err
+		}
+		flags = cmd.Flags
+	}
+
+	suggestion := SuggestFlag(flags, flag, a.HideHelp)
+	if len(suggestion) == 0 {
+		return "", err
+	}
+
+	return fmt.Sprintf(SuggestDidYouMeanTemplate+"\n\n", suggestion), nil
+}
+
 // RunAndExitOnError calls .Run() and exits non-zero if an error was returned
 //
 // Deprecated: instead you should return an error that fulfills cli.ExitCoder
@@ -359,55 +446,60 @@ func (a *App) RunAsSubcommand(ctx *Context) (err error) {
 
 	err = parseIter(set, a, ctx.Args().Tail(), ctx.shellComplete)
 	nerr := normalizeFlags(a.Flags, set)
-	context := NewContext(a, set, ctx)
+	cCtx := NewContext(a, set, ctx)
 
 	if nerr != nil {
 		_, _ = fmt.Fprintln(a.Writer, nerr)
 		_, _ = fmt.Fprintln(a.Writer)
 		if len(a.Commands) > 0 {
-			_ = ShowSubcommandHelp(context)
+			_ = ShowSubcommandHelp(cCtx)
 		} else {
-			_ = ShowCommandHelp(ctx, context.Args().First())
+			_ = ShowCommandHelp(ctx, cCtx.Args().First())
 		}
 		return nerr
 	}
 
-	if checkCompletions(context) {
+	if checkCompletions(cCtx) {
 		return nil
 	}
 
 	if err != nil {
 		if a.OnUsageError != nil {
-			err = a.OnUsageError(context, err, true)
+			err = a.OnUsageError(cCtx, err, true)
-			a.handleExitCoder(context, err)
+			a.handleExitCoder(cCtx, err)
 			return err
 		}
 		_, _ = fmt.Fprintf(a.Writer, "%s %s\n\n", "Incorrect Usage.", err.Error())
-		_ = ShowSubcommandHelp(context)
+		if a.Suggest {
+			if suggestion, err := a.suggestFlagFromError(err, cCtx.Command.Name); err == nil {
+				fmt.Fprintf(a.Writer, suggestion)
+			}
+		}
+		_ = ShowSubcommandHelp(cCtx)
 		return err
 	}
 
 	if len(a.Commands) > 0 {
-		if checkSubcommandHelp(context) {
+		if checkSubcommandHelp(cCtx) {
 			return nil
 		}
 	} else {
-		if checkCommandHelp(ctx, context.Args().First()) {
+		if checkCommandHelp(ctx, cCtx.Args().First()) {
 			return nil
 		}
 	}
 
-	cerr := context.checkRequiredFlags(a.Flags)
+	cerr := cCtx.checkRequiredFlags(a.Flags)
 	if cerr != nil {
-		_ = ShowSubcommandHelp(context)
+		_ = ShowSubcommandHelp(cCtx)
 		return cerr
 	}
 
 	if a.After != nil {
 		defer func() {
-			afterErr := a.After(context)
+			afterErr := a.After(cCtx)
 			if afterErr != nil {
-				a.handleExitCoder(context, err)
+				a.handleExitCoder(cCtx, err)
 				if err != nil {
 					err = newMultiError(err, afterErr)
 				} else {
@@ -418,27 +510,27 @@ func (a *App) RunAsSubcommand(ctx *Context) (err error) {
 	}
 
 	if a.Before != nil {
-		beforeErr := a.Before(context)
+		beforeErr := a.Before(cCtx)
 		if beforeErr != nil {
-			a.handleExitCoder(context, beforeErr)
+			a.handleExitCoder(cCtx, beforeErr)
 			err = beforeErr
 			return err
 		}
 	}
 
-	args := context.Args()
+	args := cCtx.Args()
 	if args.Present() {
 		name := args.First()
 		c := a.Command(name)
 		if c != nil {
-			return c.Run(context)
+			return c.Run(cCtx)
 		}
 	}
 
 	// Run default Action
-	err = a.Action(context)
+	err = a.Action(cCtx)
 
-	a.handleExitCoder(context, err)
+	a.handleExitCoder(cCtx, err)
 	return err
 }
 
@@ -481,6 +573,14 @@ func (a *App) VisibleCommands() []*Command {
 	return ret
 }
 
+// VisibleFlagCategories returns a slice containing all the categories with the flags they contain
+func (a *App) VisibleFlagCategories() []VisibleFlagCategory {
+	if a.flagCategories == nil {
+		return []VisibleFlagCategory{}
+	}
+	return a.flagCategories.VisibleCategories()
+}
+
 // VisibleFlags returns a slice of the Flags with Hidden=false
 func (a *App) VisibleFlags() []Flag {
 	return visibleFlags(a.Flags)
@@ -498,14 +598,49 @@ func (a *App) appendCommand(c *Command) {
 	}
 }
 
-func (a *App) handleExitCoder(context *Context, err error) {
+func (a *App) handleExitCoder(cCtx *Context, err error) {
 	if a.ExitErrHandler != nil {
-		a.ExitErrHandler(context, err)
+		a.ExitErrHandler(cCtx, err)
 	} else {
 		HandleExitCoder(err)
 	}
 }
 
+func (a *App) commandNames() []string {
+	var cmdNames []string
+
+	for _, cmd := range a.Commands {
+		cmdNames = append(cmdNames, cmd.Names()...)
+	}
+
+	return cmdNames
+}
+
+func (a *App) validCommandName(checkCmdName string) bool {
+	valid := false
+	allCommandNames := a.commandNames()
+
+	for _, cmdName := range allCommandNames {
+		if checkCmdName == cmdName {
+			valid = true
+			break
+		}
+	}
+
+	return valid
+}
+
+func (a *App) argsWithDefaultCommand(oldArgs Args) Args {
+	if a.DefaultCommand != "" {
+		rawArgs := append([]string{a.DefaultCommand}, oldArgs.Slice()...)
+		newArgs := args(rawArgs)
+
+		return &newArgs
+	}
+
+	return oldArgs
+}
+
 // Author represents someone who has contributed to a cli project.
 type Author struct {
 	Name  string // The Authors name
@@ -525,16 +660,28 @@ func (a *Author) String() string {
 // HandleAction attempts to figure out which Action signature was used.  If
 // it's an ActionFunc or a func with the legacy signature for Action, the func
 // is run!
-func HandleAction(action interface{}, context *Context) (err error) {
+func HandleAction(action interface{}, cCtx *Context) (err error) {
 	switch a := action.(type) {
 	case ActionFunc:
-		return a(context)
+		return a(cCtx)
 	case func(*Context) error:
-		return a(context)
+		return a(cCtx)
 	case func(*Context): // deprecated function signature
-		a(context)
+		a(cCtx)
 		return nil
 	}
 
 	return errInvalidActionType
 }
+
+func checkStringSliceIncludes(want string, sSlice []string) bool {
+	found := false
+	for _, s := range sSlice {
+		if want == s {
+			found = true
+			break
+		}
+	}
+
+	return found
+}

app_test.go

@@ -142,8 +142,8 @@ func ExampleApp_Run_appHelp() {
 	//    help, h        Shows a list of commands or help for one command
 	//
 	// GLOBAL OPTIONS:
-	//    --name value   a name to say (default: "bob")
 	//    --help, -h     show help (default: false)
+	//    --name value   a name to say (default: "bob")
 	//    --version, -v  print the version (default: false)
 }
 
@@ -228,6 +228,7 @@ func ExampleApp_Run_subcommandNoAction() {
 }
 
 func ExampleApp_Run_bashComplete_withShortFlag() {
+	os.Setenv("SHELL", "bash")
 	os.Args = []string{"greet", "-", "--generate-bash-completion"}
 
 	app := NewApp()
@@ -255,6 +256,7 @@ func ExampleApp_Run_bashComplete_withShortFlag() {
 }
 
 func ExampleApp_Run_bashComplete_withLongFlag() {
+	os.Setenv("SHELL", "bash")
 	os.Args = []string{"greet", "--s", "--generate-bash-completion"}
 
 	app := NewApp()
@@ -283,6 +285,7 @@ func ExampleApp_Run_bashComplete_withLongFlag() {
 	// --similar-flag
 }
 func ExampleApp_Run_bashComplete_withMultipleLongFlag() {
+	os.Setenv("SHELL", "bash")
 	os.Args = []string{"greet", "--st", "--generate-bash-completion"}
 
 	app := NewApp()
@@ -315,7 +318,7 @@ func ExampleApp_Run_bashComplete_withMultipleLongFlag() {
 }
 
 func ExampleApp_Run_bashComplete() {
-	// set args for examples sake
+	os.Setenv("SHELL", "bash")
 	os.Args = []string{"greet", "--generate-bash-completion"}
 
 	app := &App{
@@ -355,7 +358,7 @@ func ExampleApp_Run_bashComplete() {
 func ExampleApp_Run_zshComplete() {
 	// set args for examples sake
 	os.Args = []string{"greet", "--generate-bash-completion"}
-	_ = os.Setenv("_CLI_ZSH_AUTOCOMPLETE_HACK", "1")
+	_ = os.Setenv("SHELL", "/usr/bin/zsh")
 
 	app := NewApp()
 	app.Name = "greet"
@@ -390,6 +393,40 @@ func ExampleApp_Run_zshComplete() {
 	// h:Shows a list of commands or help for one command
 }
 
+func ExampleApp_Run_sliceValues() {
+	// set args for examples sake
+	os.Args = []string{"multi_values",
+		"--stringSclice", "parsed1,parsed2", "--stringSclice", "parsed3,parsed4",
+		"--float64Sclice", "13.3,14.4", "--float64Sclice", "15.5,16.6",
+		"--int64Sclice", "13,14", "--int64Sclice", "15,16",
+		"--intSclice", "13,14", "--intSclice", "15,16",
+	}
+	app := NewApp()
+	app.Name = "multi_values"
+	app.Flags = []Flag{
+		&StringSliceFlag{Name: "stringSclice"},
+		&Float64SliceFlag{Name: "float64Sclice"},
+		&Int64SliceFlag{Name: "int64Sclice"},
+		&IntSliceFlag{Name: "intSclice"},
+	}
+	app.Action = func(ctx *Context) error {
+		for i, v := range ctx.FlagNames() {
+			fmt.Printf("%d-%s %#v\n", i, v, ctx.Value(v))
+		}
+		err := ctx.Err()
+		fmt.Println("error:", err)
+		return err
+	}
+
+	_ = app.Run(os.Args)
+	// Output:
+	// 0-float64Sclice cli.Float64Slice{slice:[]float64{13.3, 14.4, 15.5, 16.6}, hasBeenSet:true}
+	// 1-int64Sclice cli.Int64Slice{slice:[]int64{13, 14, 15, 16}, hasBeenSet:true}
+	// 2-intSclice cli.IntSlice{slice:[]int{13, 14, 15, 16}, hasBeenSet:true}
+	// 3-stringSclice cli.StringSlice{slice:[]string{"parsed1", "parsed2", "parsed3", "parsed4"}, hasBeenSet:true}
+	// error: <nil>
+}
+
 func TestApp_Run(t *testing.T) {
 	s := ""
 
@@ -432,6 +469,175 @@ func TestApp_Command(t *testing.T) {
 	}
 }
 
+var defaultCommandAppTests = []struct {
+	cmdName    string
+	defaultCmd string
+	expected   bool
+}{
+	{"foobar", "foobar", true},
+	{"batbaz", "foobar", true},
+	{"b", "", true},
+	{"f", "", true},
+	{"", "foobar", true},
+	{"", "", true},
+	{" ", "", false},
+	{"bat", "batbaz", false},
+	{"nothing", "batbaz", false},
+	{"nothing", "", false},
+}
+
+func TestApp_RunDefaultCommand(t *testing.T) {
+	for _, test := range defaultCommandAppTests {
+		testTitle := fmt.Sprintf("command=%[1]s-default=%[2]s", test.cmdName, test.defaultCmd)
+		t.Run(testTitle, func(t *testing.T) {
+			app := &App{
+				DefaultCommand: test.defaultCmd,
+				Commands: []*Command{
+					{Name: "foobar", Aliases: []string{"f"}},
+					{Name: "batbaz", Aliases: []string{"b"}},
+				},
+			}
+
+			err := app.Run([]string{"c", test.cmdName})
+			expect(t, err == nil, test.expected)
+		})
+	}
+}
+
+var defaultCommandSubCmdAppTests = []struct {
+	cmdName    string
+	subCmd     string
+	defaultCmd string
+	expected   bool
+}{
+	{"foobar", "", "foobar", true},
+	{"foobar", "carly", "foobar", true},
+	{"batbaz", "", "foobar", true},
+	{"b", "", "", true},
+	{"f", "", "", true},
+	{"", "", "foobar", true},
+	{"", "", "", true},
+	{"", "jimbob", "foobar", true},
+	{"", "j", "foobar", true},
+	{"", "carly", "foobar", true},
+	{"", "jimmers", "foobar", true},
+	{"", "jimmers", "", true},
+	{" ", "jimmers", "foobar", false},
+	{"", "", "", true},
+	{" ", "", "", false},
+	{" ", "j", "", false},
+	{"bat", "", "batbaz", false},
+	{"nothing", "", "batbaz", false},
+	{"nothing", "", "", false},
+	{"nothing", "j", "batbaz", false},
+	{"nothing", "carly", "", false},
+}
+
+func TestApp_RunDefaultCommandWithSubCommand(t *testing.T) {
+	for _, test := range defaultCommandSubCmdAppTests {
+		testTitle := fmt.Sprintf("command=%[1]s-subcmd=%[2]s-default=%[3]s", test.cmdName, test.subCmd, test.defaultCmd)
+		t.Run(testTitle, func(t *testing.T) {
+			app := &App{
+				DefaultCommand: test.defaultCmd,
+				Commands: []*Command{
+					{
+						Name:    "foobar",
+						Aliases: []string{"f"},
+						Subcommands: []*Command{
+							{Name: "jimbob", Aliases: []string{"j"}},
+							{Name: "carly"},
+						},
+					},
+					{Name: "batbaz", Aliases: []string{"b"}},
+				},
+			}
+
+			err := app.Run([]string{"c", test.cmdName, test.subCmd})
+			expect(t, err == nil, test.expected)
+		})
+	}
+}
+
+var defaultCommandFlagAppTests = []struct {
+	cmdName    string
+	flag       string
+	defaultCmd string
+	expected   bool
+}{
+	{"foobar", "", "foobar", true},
+	{"foobar", "-c derp", "foobar", true},
+	{"batbaz", "", "foobar", true},
+	{"b", "", "", true},
+	{"f", "", "", true},
+	{"", "", "foobar", true},
+	{"", "", "", true},
+	{"", "-j", "foobar", true},
+	{"", "-j", "foobar", true},
+	{"", "-c derp", "foobar", true},
+	{"", "--carly=derp", "foobar", true},
+	{"", "-j", "foobar", true},
+	{"", "-j", "", true},
+	{" ", "-j", "foobar", false},
+	{"", "", "", true},
+	{" ", "", "", false},
+	{" ", "-j", "", false},
+	{"bat", "", "batbaz", false},
+	{"nothing", "", "batbaz", false},
+	{"nothing", "", "", false},
+	{"nothing", "--jimbob", "batbaz", false},
+	{"nothing", "--carly", "", false},
+}
+
+func TestApp_RunDefaultCommandWithFlags(t *testing.T) {
+	for _, test := range defaultCommandFlagAppTests {
+		testTitle := fmt.Sprintf("command=%[1]s-flag=%[2]s-default=%[3]s", test.cmdName, test.flag, test.defaultCmd)
+		t.Run(testTitle, func(t *testing.T) {
+			app := &App{
+				DefaultCommand: test.defaultCmd,
+				Flags: []Flag{
+					&StringFlag{
+						Name:     "carly",
+						Aliases:  []string{"c"},
+						Required: false,
+					},
+					&BoolFlag{
+						Name:     "jimbob",
+						Aliases:  []string{"j"},
+						Required: false,
+						Value:    true,
+					},
+				},
+				Commands: []*Command{
+					{
+						Name:    "foobar",
+						Aliases: []string{"f"},
+					},
+					{Name: "batbaz", Aliases: []string{"b"}},
+				},
+			}
+
+			appArgs := []string{"c"}
+
+			if test.flag != "" {
+				flags := strings.Split(test.flag, " ")
+				if len(flags) > 1 {
+					appArgs = append(appArgs, flags...)
+				}
+
+				flags = strings.Split(test.flag, "=")
+				if len(flags) > 1 {
+					appArgs = append(appArgs, flags...)
+				}
+			}
+
+			appArgs = append(appArgs, test.cmdName)
+
+			err := app.Run(appArgs)
+			expect(t, err == nil, test.expected)
+		})
+	}
+}
+
 func TestApp_Setup_defaultsReader(t *testing.T) {
 	app := &App{}
 	app.Setup()
@@ -445,14 +651,14 @@ func TestApp_Setup_defaultsWriter(t *testing.T) {
 }
 
 func TestApp_RunAsSubcommandParseFlags(t *testing.T) {
-	var context *Context
+	var cCtx *Context
 
 	a := &App{
 		Commands: []*Command{
 			{
 				Name: "foo",
 				Action: func(c *Context) error {
-					context = c
+					cCtx = c
 					return nil
 				},
 				Flags: []Flag{
@@ -468,8 +674,8 @@ func TestApp_RunAsSubcommandParseFlags(t *testing.T) {
 	}
 	_ = a.Run([]string{"", "foo", "--lang", "spanish", "abcd"})
 
-	expect(t, context.Args().Get(0), "abcd")
+	expect(t, cCtx.Args().Get(0), "abcd")
-	expect(t, context.String("lang"), "spanish")
+	expect(t, cCtx.String("lang"), "spanish")
 }
 
 func TestApp_RunAsSubCommandIncorrectUsage(t *testing.T) {
@@ -1890,6 +2096,14 @@ func TestApp_VisibleCategories(t *testing.T) {
 	expect(t, []CommandCategory{}, app.VisibleCategories())
 }
 
+func TestApp_VisibleFlagCategories(t *testing.T) {
+	app := &App{}
+	vfc := app.VisibleFlagCategories()
+	if len(vfc) != 0 {
+		t.Errorf("unexpected visible flag categories %+v", vfc)
+	}
+}
+
 func TestApp_Run_DoesNotOverwriteErrorFromBefore(t *testing.T) {
 	app := &App{
 		Action: func(c *Context) error { return nil },

autocomplete/zsh_autocomplete

@@ -1,14 +1,13 @@
 #compdef $PROG
 
 _cli_zsh_autocomplete() {
-
   local -a opts
   local cur
   cur=${words[-1]}
   if [[ "$cur" == "-"* ]]; then
-    opts=("${(@f)$(_CLI_ZSH_AUTOCOMPLETE_HACK=1 ${words[@]:0:#words[@]-1} ${cur} --generate-bash-completion)}")
+    opts=("${(@f)$(${words[@]:0:#words[@]-1} ${cur} --generate-bash-completion)}")
   else
-    opts=("${(@f)$(_CLI_ZSH_AUTOCOMPLETE_HACK=1 ${words[@]:0:#words[@]-1} --generate-bash-completion)}")
+    opts=("${(@f)$(${words[@]:0:#words[@]-1} --generate-bash-completion)}")
   fi
 
   if [[ "${opts[1]}" != "" ]]; then
@@ -16,8 +15,6 @@ _cli_zsh_autocomplete() {
   else
     _files
   fi
-
-  return
 }
 
 compdef _cli_zsh_autocomplete $PROG

category.go

@@ -1,10 +1,12 @@
 package cli
 
+import "sort"
+
 // CommandCategories interface allows for category manipulation
 type CommandCategories interface {
 	// AddCommand adds a command to a category, creating a new category if necessary.
 	AddCommand(category string, command *Command)
-	// categories returns a copy of the category slice
+	// Categories returns a slice of categories sorted by name
 	Categories() []CommandCategory
 }
 
@@ -77,3 +79,93 @@ func (c *commandCategory) VisibleCommands() []*Command {
 	}
 	return ret
 }
+
+// FlagCategories interface allows for category manipulation
+type FlagCategories interface {
+	// AddFlags adds a flag to a category, creating a new category if necessary.
+	AddFlag(category string, fl Flag)
+	// VisibleCategories returns a slice of visible flag categories sorted by name
+	VisibleCategories() []VisibleFlagCategory
+}
+
+type defaultFlagCategories struct {
+	m map[string]*defaultVisibleFlagCategory
+}
+
+func newFlagCategories() FlagCategories {
+	return &defaultFlagCategories{
+		m: map[string]*defaultVisibleFlagCategory{},
+	}
+}
+
+func newFlagCategoriesFromFlags(fs []Flag) FlagCategories {
+	fc := newFlagCategories()
+	for _, fl := range fs {
+		if cf, ok := fl.(CategorizableFlag); ok {
+			fc.AddFlag(cf.GetCategory(), cf)
+		}
+	}
+
+	return fc
+}
+
+func (f *defaultFlagCategories) AddFlag(category string, fl Flag) {
+	if _, ok := f.m[category]; !ok {
+		f.m[category] = &defaultVisibleFlagCategory{name: category, m: map[string]Flag{}}
+	}
+
+	f.m[category].m[fl.String()] = fl
+}
+
+func (f *defaultFlagCategories) VisibleCategories() []VisibleFlagCategory {
+	catNames := []string{}
+	for name := range f.m {
+		catNames = append(catNames, name)
+	}
+
+	sort.Strings(catNames)
+
+	ret := make([]VisibleFlagCategory, len(catNames))
+	for i, name := range catNames {
+		ret[i] = f.m[name]
+	}
+
+	return ret
+}
+
+// VisibleFlagCategory is a category containing flags.
+type VisibleFlagCategory interface {
+	// Name returns the category name string
+	Name() string
+	// Flags returns a slice of VisibleFlag sorted by name
+	Flags() []VisibleFlag
+}
+
+type defaultVisibleFlagCategory struct {
+	name string
+	m    map[string]Flag
+}
+
+func (fc *defaultVisibleFlagCategory) Name() string {
+	return fc.name
+}
+
+func (fc *defaultVisibleFlagCategory) Flags() []VisibleFlag {
+	vfNames := []string{}
+	for flName, fl := range fc.m {
+		if vf, ok := fl.(VisibleFlag); ok {
+			if vf.IsVisible() {
+				vfNames = append(vfNames, flName)
+			}
+		}
+	}
+
+	sort.Strings(vfNames)
+
+	ret := make([]VisibleFlag, len(vfNames))
+	for i, flName := range vfNames {
+		ret[i] = fc.m[flName].(VisibleFlag)
+	}
+
+	return ret
+}

cli.go

@@ -20,4 +20,4 @@
 //   }
 package cli
 
-//go:generate go run flag-gen/main.go flag-gen/assets_vfsdata.go
+//go:generate go run internal/genflags/cmd/genflags/main.go

command.go

@@ -38,7 +38,8 @@ type Command struct {
 	// List of child commands
 	Subcommands []*Command
 	// List of flags to parse
-	Flags []Flag
+	Flags          []Flag
+	flagCategories FlagCategories
 	// Treat all flags as normal arguments if true
 	SkipFlagParsing bool
 	// Boolean to hide built-in help command and help flag
@@ -105,39 +106,44 @@ func (c *Command) Run(ctx *Context) (err error) {
 
 	set, err := c.parseFlags(ctx.Args(), ctx.shellComplete)
 
-	context := NewContext(ctx.App, set, ctx)
+	cCtx := NewContext(ctx.App, set, ctx)
-	context.Command = c
+	cCtx.Command = c
-	if checkCommandCompletions(context, c.Name) {
+	if checkCommandCompletions(cCtx, c.Name) {
 		return nil
 	}
 
 	if err != nil {
 		if c.OnUsageError != nil {
-			err = c.OnUsageError(context, err, false)
+			err = c.OnUsageError(cCtx, err, false)
-			context.App.handleExitCoder(context, err)
+			cCtx.App.handleExitCoder(cCtx, err)
 			return err
 		}
-		_, _ = fmt.Fprintln(context.App.Writer, "Incorrect Usage:", err.Error())
+		_, _ = fmt.Fprintln(cCtx.App.Writer, "Incorrect Usage:", err.Error())
-		_, _ = fmt.Fprintln(context.App.Writer)
+		_, _ = fmt.Fprintln(cCtx.App.Writer)
-		_ = ShowCommandHelp(context, c.Name)
+		if ctx.App.Suggest {
+			if suggestion, err := ctx.App.suggestFlagFromError(err, c.Name); err == nil {
+				fmt.Fprintf(cCtx.App.Writer, suggestion)
+			}
+		}
+		_ = ShowCommandHelp(cCtx, c.Name)
 		return err
 	}
 
-	if checkCommandHelp(context, c.Name) {
+	if checkCommandHelp(cCtx, c.Name) {
 		return nil
 	}
 
-	cerr := context.checkRequiredFlags(c.Flags)
+	cerr := cCtx.checkRequiredFlags(c.Flags)
 	if cerr != nil {
-		_ = ShowCommandHelp(context, c.Name)
+		_ = ShowCommandHelp(cCtx, c.Name)
 		return cerr
 	}
 
 	if c.After != nil {
 		defer func() {
-			afterErr := c.After(context)
+			afterErr := c.After(cCtx)
 			if afterErr != nil {
-				context.App.handleExitCoder(context, err)
+				cCtx.App.handleExitCoder(cCtx, err)
 				if err != nil {
 					err = newMultiError(err, afterErr)
 				} else {
@@ -148,9 +154,9 @@ func (c *Command) Run(ctx *Context) (err error) {
 	}
 
 	if c.Before != nil {
-		err = c.Before(context)
+		err = c.Before(cCtx)
 		if err != nil {
-			context.App.handleExitCoder(context, err)
+			cCtx.App.handleExitCoder(cCtx, err)
 			return err
 		}
 	}
@@ -159,11 +165,11 @@ func (c *Command) Run(ctx *Context) (err error) {
 		c.Action = helpSubcommand.Action
 	}
 
-	context.Command = c
+	cCtx.Command = c
-	err = c.Action(context)
+	err = c.Action(cCtx)
 
 	if err != nil {
-		context.App.handleExitCoder(context, err)
+		cCtx.App.handleExitCoder(cCtx, err)
 	}
 	return err
 }
@@ -249,6 +255,7 @@ func (c *Command) startApp(ctx *Context) error {
 	app.ErrWriter = ctx.App.ErrWriter
 	app.ExitErrHandler = ctx.App.ExitErrHandler
 	app.UseShortOptionHandling = ctx.App.UseShortOptionHandling
+	app.Suggest = ctx.App.Suggest
 
 	app.categories = newCommandCategories()
 	for _, command := range c.Subcommands {
@@ -280,6 +287,14 @@ func (c *Command) startApp(ctx *Context) error {
 	return app.RunAsSubcommand(ctx)
 }
 
+// VisibleFlagCategories returns a slice containing all the visible flag categories with the flags they contain
+func (c *Command) VisibleFlagCategories() []VisibleFlagCategory {
+	if c.flagCategories == nil {
+		return []VisibleFlagCategory{}
+	}
+	return c.flagCategories.VisibleCategories()
+}
+
 // VisibleFlags returns a slice of the Flags with Hidden=false
 func (c *Command) VisibleFlags() []Flag {
 	return visibleFlags(c.Flags)

command_test.go

@@ -30,7 +30,7 @@ func TestCommandFlagParsing(t *testing.T) {
 		set := flag.NewFlagSet("test", 0)
 		_ = set.Parse(c.testArgs)
 
-		context := NewContext(app, set, nil)
+		cCtx := NewContext(app, set, nil)
 
 		command := Command{
 			Name:            "test-cmd",
@@ -41,10 +41,10 @@ func TestCommandFlagParsing(t *testing.T) {
 			SkipFlagParsing: c.skipFlagParsing,
 		}
 
-		err := command.Run(context)
+		err := command.Run(cCtx)
 
 		expect(t, err, c.expectedErr)
-		expect(t, context.Args().Slice(), c.testArgs)
+		expect(t, cCtx.Args().Slice(), c.testArgs)
 	}
 }
 

context.go

@@ -40,18 +40,18 @@ func NewContext(app *App, set *flag.FlagSet, parentCtx *Context) *Context {
 }
 
 // NumFlags returns the number of flags set
-func (c *Context) NumFlags() int {
+func (cCtx *Context) NumFlags() int {
-	return c.flagSet.NFlag()
+	return cCtx.flagSet.NFlag()
 }
 
 // Set sets a context flag to a value.
-func (c *Context) Set(name, value string) error {
+func (cCtx *Context) Set(name, value string) error {
-	return c.flagSet.Set(name, value)
+	return cCtx.flagSet.Set(name, value)
 }
 
 // IsSet determines if the flag was actually set
-func (c *Context) IsSet(name string) bool {
+func (cCtx *Context) IsSet(name string) bool {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		isSet := false
 		fs.Visit(func(f *flag.Flag) {
 			if f.Name == name {
@@ -62,7 +62,7 @@ func (c *Context) IsSet(name string) bool {
 			return true
 		}
 
-		f := c.lookupFlag(name)
+		f := cCtx.lookupFlag(name)
 		if f == nil {
 			return false
 		}
@@ -74,28 +74,28 @@ func (c *Context) IsSet(name string) bool {
 }
 
 // LocalFlagNames returns a slice of flag names used in this context.
-func (c *Context) LocalFlagNames() []string {
+func (cCtx *Context) LocalFlagNames() []string {
 	var names []string
-	c.flagSet.Visit(makeFlagNameVisitor(&names))
+	cCtx.flagSet.Visit(makeFlagNameVisitor(&names))
 	return names
 }
 
 // FlagNames returns a slice of flag names used by the this context and all of
 // its parent contexts.
-func (c *Context) FlagNames() []string {
+func (cCtx *Context) FlagNames() []string {
 	var names []string
-	for _, ctx := range c.Lineage() {
+	for _, pCtx := range cCtx.Lineage() {
-		ctx.flagSet.Visit(makeFlagNameVisitor(&names))
+		pCtx.flagSet.Visit(makeFlagNameVisitor(&names))
 	}
 	return names
 }
 
 // Lineage returns *this* context and all of its ancestor contexts in order from
 // child to parent
-func (c *Context) Lineage() []*Context {
+func (cCtx *Context) Lineage() []*Context {
 	var lineage []*Context
 
-	for cur := c; cur != nil; cur = cur.parentContext {
+	for cur := cCtx; cur != nil; cur = cur.parentContext {
 		lineage = append(lineage, cur)
 	}
 
@@ -103,26 +103,26 @@ func (c *Context) Lineage() []*Context {
 }
 
 // Value returns the value of the flag corresponding to `name`
-func (c *Context) Value(name string) interface{} {
+func (cCtx *Context) Value(name string) interface{} {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return fs.Lookup(name).Value.(flag.Getter).Get()
 	}
 	return nil
 }
 
 // Args returns the command line arguments associated with the context.
-func (c *Context) Args() Args {
+func (cCtx *Context) Args() Args {
-	ret := args(c.flagSet.Args())
+	ret := args(cCtx.flagSet.Args())
 	return &ret
 }
 
 // NArg returns the number of the command line arguments.
-func (c *Context) NArg() int {
+func (cCtx *Context) NArg() int {
-	return c.Args().Len()
+	return cCtx.Args().Len()
 }
 
-func (ctx *Context) lookupFlag(name string) Flag {
+func (cCtx *Context) lookupFlag(name string) Flag {
-	for _, c := range ctx.Lineage() {
+	for _, c := range cCtx.Lineage() {
 		if c.Command == nil {
 			continue
 		}
@@ -136,8 +136,8 @@ func (ctx *Context) lookupFlag(name string) Flag {
 		}
 	}
 
-	if ctx.App != nil {
+	if cCtx.App != nil {
-		for _, f := range ctx.App.Flags {
+		for _, f := range cCtx.App.Flags {
 			for _, n := range f.Names() {
 				if n == name {
 					return f
@@ -149,8 +149,8 @@ func (ctx *Context) lookupFlag(name string) Flag {
 	return nil
 }
 
-func (ctx *Context) lookupFlagSet(name string) *flag.FlagSet {
+func (cCtx *Context) lookupFlagSet(name string) *flag.FlagSet {
-	for _, c := range ctx.Lineage() {
+	for _, c := range cCtx.Lineage() {
 		if c.flagSet == nil {
 			continue
 		}
@@ -162,7 +162,7 @@ func (ctx *Context) lookupFlagSet(name string) *flag.FlagSet {
 	return nil
 }
 
-func (context *Context) checkRequiredFlags(flags []Flag) requiredFlagsErr {
+func (cCtx *Context) checkRequiredFlags(flags []Flag) requiredFlagsErr {
 	var missingFlags []string
 	for _, f := range flags {
 		if rf, ok := f.(RequiredFlag); ok && rf.IsRequired() {
@@ -174,7 +174,7 @@ func (context *Context) checkRequiredFlags(flags []Flag) requiredFlagsErr {
 					flagName = key
 				}
 
-				if context.IsSet(strings.TrimSpace(key)) {
+				if cCtx.IsSet(strings.TrimSpace(key)) {
 					flagPresent = true
 				}
 			}

docs.go

@@ -1,3 +1,6 @@
+//go:build !urfave_cli_no_docs
+// +build !urfave_cli_no_docs
+
 package cli
 
 import (
@@ -80,14 +83,14 @@ func prepareCommands(commands []*Command, level int) []string {
 			usageText,
 		)
 
-		flags := prepareArgsWithValues(command.Flags)
+		flags := prepareArgsWithValues(command.VisibleFlags())
 		if len(flags) > 0 {
 			prepared += fmt.Sprintf("\n%s", strings.Join(flags, "\n"))
 		}
 
 		coms = append(coms, prepared)
 
-		// recursevly iterate subcommands
+		// recursively iterate subcommands
 		if len(command.Subcommands) > 0 {
 			coms = append(
 				coms,

docs/CHANGELOG.md

@@ -1,3 +1,9 @@
+> :warning: This document is no longer being actively maintained. Please see the
+> [releases page](https://github.com/urfave/cli/releases) for all release notes
+> and related hypermedia for releases `>= 1.22.5`, `>= 2.3.0`.
+
+---
+
 # Change Log
 
 **ATTN**: This project uses [semantic versioning](http://semver.org/).

docs/CNAME

@@ -0,0 +1 @@
+cli.urfave.org

docs/CODE_OF_CONDUCT.md

@@ -0,0 +1 @@
+../CODE_OF_CONDUCT.md

docs/CONTRIBUTING.md

@@ -1,18 +1,143 @@
 ## Contributing
 
-Use @urfave/cli to ping the maintainers.
+Welcome to the `urfave/cli` contributor docs! This goal of this document is to help those
+interested in joining the 200+ humans who have contributed to this project over the years.
 
-Feel free to put up a pull request to fix a bug or maybe add a feature. We will
+> As a general guiding principle, the current maintainers may be notified via the
-give it a code review and make sure that it does not break backwards
+> @urfave/cli GitHub team.
-compatibility. If collaborators agree that it is in line with
-the vision of the project, we will work with you to get the code into
-a mergeable state and merge it into the main branch.
 
-If you have contributed something significant to the project, we will most
+All of the current maintainers are *volunteers* who live in various timezones with
-likely add you as a collaborator. As a collaborator you are given the ability
+different scheduling needs, so please understand that your contribution or question may
-to merge others pull requests. It is very important that new code does not
+not get a response for many days.
-break existing code, so be careful about what code you do choose to merge.
 
-If you feel like you have contributed to the project but have not yet been added
+### semantic versioning adherence
-as a collaborator, we probably forgot to add you :sweat_smile:. Please open an
+
-issue!
+The `urfave/cli` project strives to strictly adhere to [semantic
+versioning](https://semver.org/spec/v2.0.0.html). The active development branches and the
+milestones and import paths to which they correspond are:
+
+#### `main` branch
+
+<https://github.com/urfave/cli/tree/main>
+
+The majority of active development and issue management is targeting the `main` branch,
+which **MUST** *only* receive bug fixes and feature *additions*.
+
+- :arrow_right: [`v2.x`](https://github.com/urfave/cli/milestone/16)
+- :arrow_right: `github.com/urfave/cli/v2`
+
+The `main` branch in particular includes tooling to help with keeping the `v2.x` series
+backward compatible. More details on this process are in the development workflow section
+below.
+
+#### `v1` branch
+
+<https://github.com/urfave/cli/tree/v1>
+
+The `v1` branch **MUST** only receive bug fixes in the `v1.22.x` series. There is no
+strict rule regarding bug fixes to the `v2.x` series being backported to the `v1.22.x`
+series.
+
+- :arrow_right: [`v1.22.x`](https://github.com/urfave/cli/milestone/11)
+- :arrow_right: `github.com/urfave/cli`
+
+#### `v3-dev-main` branch
+
+<https://github.com/urfave/cli/tree/v3-dev-main>
+
+The `v3-dev-branch` **MUST** receive all bug fixes and features added to the `main` branch
+and **MAY** receive feature *removals* and other changes that are otherwise
+*backward-incompatible* with the `v2.x` series.
+
+- :arrow_right: [`v3.x`](https://github.com/urfave/cli/milestone/5)
+- unreleased / unsupported
+
+### development workflow
+
+Most of the tooling around the development workflow strives for effective
+[dogfooding](https://en.wikipedia.org/wiki/Eating_your_own_dog_food). There is a top-level
+`Makefile` that is maintained strictly for the purpose of easing verification of one's
+development environment and any changes one may have introduced:
+
+```sh
+make
+```
+
+Running the default `make` target (`all`) will ensure all of the critical steps are run to
+verify one's changes are harmonious in nature. The same steps are also run during the
+[continuous integration
+phase](https://github.com/urfave/cli/blob/main/.github/workflows/cli.yml).
+
+In the event that the `v2diff` target exits non-zero, this is a signal that the public API
+surface area has changed. If the changes adhere to semantic versioning, meaning they are
+*additions* or *bug fixes*, then manually running the approval step will "promote" the
+current `go doc` output:
+
+```sh
+make v2approve
+```
+
+Because the `generate` step includes updating `godoc-current.txt` and
+`testdata/godoc-v2.x.txt`, these changes *MUST* be part of any proposed pull request so
+that reviewers have an opportunity to also make an informed decision about the "promotion"
+step.
+
+#### generated code
+
+A significant portion of the project's source code is generated, with the goal being to
+eliminate repetitive maintenance where other type-safe abstraction is impractical or
+impossible with Go versions `< 1.18`. In a future where the eldest Go version supported is
+`1.18.x`, there will likely be efforts to take advantage of
+[generics](https://go.dev/doc/tutorial/generics).
+
+The built-in `go generate` command is used to run the commands specified in
+`//go:generate` directives. Each such command runs a file that also supports a command
+line help system which may be consulted for further information, e.g.:
+
+```sh
+go run internal/genflags/cmd/genflags/main.go --help
+```
+
+#### docs output
+
+The documentation in the `docs` directory is automatically built via `mkdocs` into a
+static site and published when releases are pushed (see [RELEASING](./RELEASING/)). There
+is no strict requirement to build the documentation when developing locally, but the
+following `make` targets may be used if desired:
+
+```sh
+# install documentation dependencies with `pip`
+make docs-deps
+```
+
+```sh
+# build the static site in `./site`
+make docs
+```
+
+```sh
+# start an mkdocs development server
+make serve-docs
+```
+
+### pull requests
+
+Please feel free to open a pull request to fix a bug or add a feature. The @urfave/cli
+team will review it as soon as possible, giving special attention to maintaining backward
+compatibility. If the @urfave/cli team agrees that your contribution is in line with the
+vision of the project, they will work with you to get the code into a mergeable state,
+merged, and then released.
+
+### granting of commit bit / admin mode
+
+Those with a history of contributing to this project will likely be invited to join the
+@urfave/cli team. As a member of the @urfave/cli team, you will have the ability to fully
+administer pull requests, issues, and other repository bits.
+
+If you feel that you should be a member of the @urfave/cli team but have not yet been
+added, the most likely explanation is that this is an accidental oversight! :sweat_smile:.
+Please open an issue!
+
+<!--
+vim:tw=90
+-->

docs/RELEASING.md

@@ -0,0 +1,61 @@
+# Releasing urfave/cli
+
+Releasing small batches often is [backed by
+research](https://itrevolution.com/accelerate-book/) as part of the
+virtuous cycles that keep teams and products healthy.
+
+To that end, the overall goal of the release process is to send
+changes out into the world as close to the time the commits were
+merged to the `main` branch as possible. In this way, the community
+of humans depending on this library are able to make use of the
+changes they need **quickly**, which means they shouldn't have to
+maintain long-lived forks of the project, which means they can get
+back to focusing on the work on which they want to focus. This also
+means that the @urfave/cli team should be able to focus on
+delivering a steadily improving product with significantly eased
+ability to associate bugs and regressions with specific releases.
+
+## Process
+
+- Release versions follow [semantic versioning](https://semver.org/)
+- Releases are associated with **signed, annotated git tags**[^1].
+- Release notes are **automatically generated**[^2].
+
+In the `main` or `v1` branch, the current version is always
+available via:
+
+```sh
+git describe --always --dirty --tags
+```
+
+**NOTE**: if the version reported contains `-dirty`, this is
+indicative of a "dirty" work tree, which is not a great state for
+creating a new release tag. Seek help from @urfave/cli teammates.
+
+For example, given a described version of `v2.4.7-3-g68da1cd` and a
+diff of `v2.4.7...` that contains only bug fixes, the next version
+should be `v2.4.8`:
+
+```sh
+git tag -a -s -m 'Release 2.4.8' v2.4.8
+git push origin v2.4.8
+```
+
+The tag push will trigger a GitHub Actions workflow. The remaining
+steps require human intervention through the GitHub web view
+although [automated solutions
+exist](https://github.com/softprops/action-gh-release) that may be
+adopted in the future.
+
+- Open the [the new release page](https://github.com/urfave/cli/releases/new)
+- At the top of the form, click on the `Choose a tag` select control and select `v2.4.8`
+- In the `Write` tab below, click the `Auto-generate release notes` button
+- At the bottom of the form, click the `Publish release` button
+- :white_check_mark: you're done!
+
+[^1]: This was not always true. There are many **lightweight git
+  tags** present in the repository history.
+
+[^2]: This was not always true. The
+  [`docs/CHANGELOG.md`](./CHANGELOG.md) document used to be
+  manually maintained.

docs/SECURITY.md

@@ -0,0 +1,27 @@
+# Security Policy
+
+Hello and thank you for your interest in the `urfave/cli` security
+policy! :tada: :lock:
+
+## Supported Versions
+
+| Version      | Supported                             |
+| ------------ | ------------------------------------- |
+| `>= v2.3.x`  | :white_check_mark:                    |
+| `< v2.3`     | :x:                                   |
+| `>= v1.22.x` | :white_check_mark: :lady_beetle: [^1] |
+| `< v1.22`    | :x:                                   |
+
+## Reporting a Vulnerability
+
+Please disclose any vulnerabilities by sending an email to:
+
+[urfave-security@googlegroups.com](mailto:urfave-security@googlegroups.com)
+
+You should expect a response within 48 hours and further
+communications to be decided via email. The `urfave/cli` maintainer
+team comprises volunteers who contribute when possible, so please
+have patience :bow:
+
+[^1]: The `v1.22.x` series will receive bug fixes and security
+  patches only.

docs/index.md

@@ -0,0 +1,73 @@
+# Welcome to urfave/cli
+
+[![GoDoc](https://godoc.org/github.com/urfave/cli?status.svg)](https://pkg.go.dev/github.com/urfave/cli/v2)
+[![codebeat](https://codebeat.co/badges/0a8f30aa-f975-404b-b878-5fab3ae1cc5f)](https://codebeat.co/projects/github-com-urfave-cli)
+[![Go Report Card](https://goreportcard.com/badge/urfave/cli)](https://goreportcard.com/report/urfave/cli)
+[![codecov](https://codecov.io/gh/urfave/cli/branch/main/graph/badge.svg)](https://codecov.io/gh/urfave/cli)
+
+`urfave/cli` is a simple, fast, and fun package for building command line apps in Go. The
+goal is to enable developers to write fast and distributable command line applications in
+an expressive way.
+
+These are the guides for each major supported version:
+
+- [`v2`](./v2/)
+- [`v1`](./v1/)
+
+In addition to the version-specific guides, these other documents are available:
+
+- [CONTRIBUTING](./CONTRIBUTING/)
+- [CODE OF CONDUCT](./CODE_OF_CONDUCT/)
+- [RELEASING](./RELEASING/)
+
+## Installation
+
+Using this package requires a working Go environment. [See the install instructions for Go](http://golang.org/doc/install.html).
+
+Go Modules are required when using this package. [See the go blog guide on using Go Modules](https://blog.golang.org/using-go-modules).
+
+### Using `v2` releases
+
+```
+$ go get github.com/urfave/cli/v2
+```
+
+```go
+...
+import (
+  "github.com/urfave/cli/v2" // imports as package "cli"
+)
+...
+```
+
+### Using `v1` releases
+
+```
+$ go get github.com/urfave/cli
+```
+
+```go
+...
+import (
+  "github.com/urfave/cli"
+)
+...
+```
+
+### Build tags
+
+You can use the following build tags:
+
+#### `urfave_cli_no_docs`
+
+When set, this removes `ToMarkdown` and `ToMan` methods, so your application
+won't be able to call those. This reduces the resulting binary size by about
+300-400 KB (measured using Go 1.18.1 on Linux/amd64), due to fewer dependencies.
+
+### Supported platforms
+
+cli is tested against multiple versions of Go on Linux, and against the latest
+released version of Go on OS X and Windows. This project uses Github Actions
+for builds. To see our currently supported go versions and platforms, look at
+the [github workflow
+configuration](https://github.com/urfave/cli/blob/main/.github/workflows/cli.yml).

docs/migrate-v1-to-v2.md

@@ -1,6 +1,4 @@
-Migration Guide: v1 to v2
+# Migration Guide: v1 to v2
-===
-
 
 v2 has a number of breaking changes but converting is relatively
 straightforward: make the changes documented below then resolve any
@@ -11,25 +9,6 @@ If you find any issues not covered by this document, please post a
 comment on [Issue 921](https://github.com/urfave/cli/issues/921) or
 consider sending a PR to help improve this guide.
 
-<!-- toc -->
-
-  * [Flags before args](#flags-before-args)
-  * [Import string changed](#import-string-changed)
-  * [Flag aliases are done differently](#flag-aliases-are-done-differently)
-  * [EnvVar is now a list (EnvVars)](#envvar-is-now-a-list-envvars)
-  * [Actions returns errors](#actions-returns-errors)
-  * [cli.Flag changed](#cliflag-changed)
-  * [Commands are now lists of pointers](#commands-are-now-lists-of-pointers)
-  * [Lists of commands should be pointers](#lists-of-commands-should-be-pointers)
-  * [Appending Commands](#appending-commands)
-  * [GlobalString, GlobalBool and its likes are deprecated](#globalstring-globalbool-and-its-likes-are-deprecated)
-  * [BoolTFlag and BoolT are deprecated](#booltflag-and-boolt-are-deprecated)
-  * [&cli.StringSlice{""} replaced with cli.NewStringSlice("")](#clistringslice-replaced-with-clinewstringslice)
-  * [Replace deprecated functions](#replace-deprecated-functions)
-  * [Everything else](#everything-else)
-
-<!-- tocstop -->
-
 # Flags before args
 
 In v2 flags must come before args. This is more POSIX-compliant.  You

docs/v1/index.md

@@ -0,0 +1 @@
+manual.md

docs/v1/manual.md

@@ -1,35 +1,4 @@
-cli v1 manual
+# v1 guide
-===
-
-<!-- toc -->
-
-- [Getting Started](#getting-started)
-- [Examples](#examples)
-  * [Arguments](#arguments)
-  * [Flags](#flags)
-    + [Placeholder Values](#placeholder-values)
-    + [Alternate Names](#alternate-names)
-    + [Ordering](#ordering)
-    + [Values from the Environment](#values-from-the-environment)
-    + [Values from files](#values-from-files)
-    + [Values from alternate input sources (YAML, TOML, and others)](#values-from-alternate-input-sources-yaml-toml-and-others)
-    + [Precedence](#precedence)
-  * [Subcommands](#subcommands)
-  * [Subcommands categories](#subcommands-categories)
-  * [Exit code](#exit-code)
-  * [Combining short options](#combining-short-options)
-  * [Bash Completion](#bash-completion)
-    + [Enabling](#enabling)
-    + [Distribution](#distribution)
-    + [Customization](#customization)
-  * [Generated Help Text](#generated-help-text)
-    + [Customization](#customization-1)
-  * [Version Flag](#version-flag)
-    + [Customization](#customization-2)
-    + [Full API Example](#full-api-example)
-  * [Migrating to V2](#migrating-to-v2)
-
-<!-- tocstop -->
 
 ## Getting Started
 

docs/v2/index.md

@@ -0,0 +1 @@
+manual.md

docs_test.go

@@ -1,133 +1,13 @@
+//go:build !urfave_cli_no_docs
+// +build !urfave_cli_no_docs
+
 package cli
 
 import (
-	"bytes"
 	"errors"
-	"io/ioutil"
 	"testing"
 )
 
-func testApp() *App {
-	app := newTestApp()
-	app.Name = "greet"
-	app.Flags = []Flag{
-		&StringFlag{
-			Name:      "socket",
-			Aliases:   []string{"s"},
-			Usage:     "some 'usage' text",
-			Value:     "value",
-			TakesFile: true,
-		},
-		&StringFlag{Name: "flag", Aliases: []string{"fl", "f"}},
-		&BoolFlag{
-			Name:    "another-flag",
-			Aliases: []string{"b"},
-			Usage:   "another usage text",
-		},
-		&BoolFlag{
-			Name:   "hidden-flag",
-			Hidden: true,
-		},
-	}
-	app.Commands = []*Command{{
-		Aliases: []string{"c"},
-		Flags: []Flag{
-			&StringFlag{
-				Name:      "flag",
-				Aliases:   []string{"fl", "f"},
-				TakesFile: true,
-			},
-			&BoolFlag{
-				Name:    "another-flag",
-				Aliases: []string{"b"},
-				Usage:   "another usage text",
-			},
-		},
-		Name:  "config",
-		Usage: "another usage test",
-		Subcommands: []*Command{{
-			Aliases: []string{"s", "ss"},
-			Flags: []Flag{
-				&StringFlag{Name: "sub-flag", Aliases: []string{"sub-fl", "s"}},
-				&BoolFlag{
-					Name:    "sub-command-flag",
-					Aliases: []string{"s"},
-					Usage:   "some usage text",
-				},
-			},
-			Name:  "sub-config",
-			Usage: "another usage test",
-		}},
-	}, {
-		Aliases: []string{"i", "in"},
-		Name:    "info",
-		Usage:   "retrieve generic information",
-	}, {
-		Name: "some-command",
-	}, {
-		Name:   "hidden-command",
-		Hidden: true,
-	}, {
-		Aliases: []string{"u"},
-		Flags: []Flag{
-			&StringFlag{
-				Name:      "flag",
-				Aliases:   []string{"fl", "f"},
-				TakesFile: true,
-			},
-			&BoolFlag{
-				Name:    "another-flag",
-				Aliases: []string{"b"},
-				Usage:   "another usage text",
-			},
-		},
-		Name:  "usage",
-		Usage: "standard usage text",
-		UsageText: `
-Usage for the usage text
-- formatted:  Based on the specified ConfigMap and summon secrets.yml
-- list:       Inspect the environment for a specific process running on a Pod
-- for_effect: Compare 'namespace' environment with 'local'
-
-` + "```" + `
-func() { ... }
-` + "```" + `
-
-Should be a part of the same code block
-`,
-		Subcommands: []*Command{{
-			Aliases: []string{"su"},
-			Flags: []Flag{
-				&BoolFlag{
-					Name:    "sub-command-flag",
-					Aliases: []string{"s"},
-					Usage:   "some usage text",
-				},
-			},
-			Name:      "sub-usage",
-			Usage:     "standard usage text",
-			UsageText: "Single line of UsageText",
-		}},
-	}}
-	app.UsageText = "app [first_arg] [second_arg]"
-	app.Description = `Description of the application.`
-	app.Usage = "Some app"
-	app.Authors = []*Author{
-		{Name: "Harrison", Email: "harrison@lolwut.com"},
-		{Name: "Oliver Allen", Email: "oliver@toyshop.com"},
-	}
-	return app
-}
-
-func expectFileContent(t *testing.T, file, got string) {
-	data, err := ioutil.ReadFile(file)
-	// Ignore windows line endings
-	// TODO: Replace with bytes.ReplaceAll when support for Go 1.11 is dropped
-	data = bytes.Replace(data, []byte("\r\n"), []byte("\n"), -1)
-	expect(t, err, nil)
-	expect(t, got, string(data))
-}
-
 func TestToMarkdownFull(t *testing.T) {
 	// Given
 	app := testApp()

fish.go

@@ -95,7 +95,7 @@ func (a *App) prepareFishCommands(commands []*Command, allCommands *[]string, pr
 		completions = append(completions, completion.String())
 		completions = append(
 			completions,
-			a.prepareFishFlags(command.Flags, command.Names())...,
+			a.prepareFishFlags(command.VisibleFlags(), command.Names())...,
 		)
 
 		// recursevly iterate subcommands

fish_test.go

@@ -1,6 +1,8 @@
 package cli
 
 import (
+	"bytes"
+	"io/ioutil"
 	"testing"
 )
 
@@ -19,3 +21,124 @@ func TestFishCompletion(t *testing.T) {
 	expect(t, err, nil)
 	expectFileContent(t, "testdata/expected-fish-full.fish", res)
 }
+
+func testApp() *App {
+	app := newTestApp()
+	app.Name = "greet"
+	app.Flags = []Flag{
+		&StringFlag{
+			Name:      "socket",
+			Aliases:   []string{"s"},
+			Usage:     "some 'usage' text",
+			Value:     "value",
+			TakesFile: true,
+		},
+		&StringFlag{Name: "flag", Aliases: []string{"fl", "f"}},
+		&BoolFlag{
+			Name:    "another-flag",
+			Aliases: []string{"b"},
+			Usage:   "another usage text",
+		},
+		&BoolFlag{
+			Name:   "hidden-flag",
+			Hidden: true,
+		},
+	}
+	app.Commands = []*Command{{
+		Aliases: []string{"c"},
+		Flags: []Flag{
+			&StringFlag{
+				Name:      "flag",
+				Aliases:   []string{"fl", "f"},
+				TakesFile: true,
+			},
+			&BoolFlag{
+				Name:    "another-flag",
+				Aliases: []string{"b"},
+				Usage:   "another usage text",
+			},
+		},
+		Name:  "config",
+		Usage: "another usage test",
+		Subcommands: []*Command{{
+			Aliases: []string{"s", "ss"},
+			Flags: []Flag{
+				&StringFlag{Name: "sub-flag", Aliases: []string{"sub-fl", "s"}},
+				&BoolFlag{
+					Name:    "sub-command-flag",
+					Aliases: []string{"s"},
+					Usage:   "some usage text",
+				},
+			},
+			Name:  "sub-config",
+			Usage: "another usage test",
+		}},
+	}, {
+		Aliases: []string{"i", "in"},
+		Name:    "info",
+		Usage:   "retrieve generic information",
+	}, {
+		Name: "some-command",
+	}, {
+		Name:   "hidden-command",
+		Hidden: true,
+	}, {
+		Aliases: []string{"u"},
+		Flags: []Flag{
+			&StringFlag{
+				Name:      "flag",
+				Aliases:   []string{"fl", "f"},
+				TakesFile: true,
+			},
+			&BoolFlag{
+				Name:    "another-flag",
+				Aliases: []string{"b"},
+				Usage:   "another usage text",
+			},
+		},
+		Name:  "usage",
+		Usage: "standard usage text",
+		UsageText: `
+Usage for the usage text
+- formatted:  Based on the specified ConfigMap and summon secrets.yml
+- list:       Inspect the environment for a specific process running on a Pod
+- for_effect: Compare 'namespace' environment with 'local'
+
+` + "```" + `
+func() { ... }
+` + "```" + `
+
+Should be a part of the same code block
+`,
+		Subcommands: []*Command{{
+			Aliases: []string{"su"},
+			Flags: []Flag{
+				&BoolFlag{
+					Name:    "sub-command-flag",
+					Aliases: []string{"s"},
+					Usage:   "some usage text",
+				},
+			},
+			Name:      "sub-usage",
+			Usage:     "standard usage text",
+			UsageText: "Single line of UsageText",
+		}},
+	}}
+	app.UsageText = "app [first_arg] [second_arg]"
+	app.Description = `Description of the application.`
+	app.Usage = "Some app"
+	app.Authors = []*Author{
+		{Name: "Harrison", Email: "harrison@lolwut.com"},
+		{Name: "Oliver Allen", Email: "oliver@toyshop.com"},
+	}
+	return app
+}
+
+func expectFileContent(t *testing.T, file, got string) {
+	data, err := ioutil.ReadFile(file)
+	// Ignore windows line endings
+	// TODO: Replace with bytes.ReplaceAll when support for Go 1.11 is dropped
+	data = bytes.Replace(data, []byte("\r\n"), []byte("\n"), -1)
+	expect(t, err, nil)
+	expect(t, got, string(data))
+}

flag-spec.yaml

@@ -0,0 +1,51 @@
+# NOTE: this file is used by the tool defined in
+# ./internal/genflags/cmd/genflags/main.go which uses the
+# `genflags.Spec` type that maps to this file structure.
+
+flag_types:
+  bool: {}
+  float64: {}
+  int64: {}
+  int: {}
+  time.Duration: {}
+  uint64: {}
+  uint: {}
+
+  string:
+    struct_fields:
+      - { name: TakesFile, type: bool }
+  Generic:
+    struct_fields:
+      - { name: TakesFile, type: bool }
+  Path:
+    struct_fields:
+      - { name: TakesFile, type: bool }
+
+  Float64Slice:
+    value_pointer: true
+    skip_interfaces:
+      - fmt.Stringer
+  Int64Slice:
+    value_pointer: true
+    skip_interfaces:
+      - fmt.Stringer
+  IntSlice:
+    value_pointer: true
+    skip_interfaces:
+      - fmt.Stringer
+  StringSlice:
+    value_pointer: true
+    skip_interfaces:
+      - fmt.Stringer
+    struct_fields:
+      - { name: TakesFile, type: bool }
+  Timestamp:
+    value_pointer: true
+    struct_fields:
+      - { name: Layout, type: string }
+      - { name: Timezone, type: "*time.Location" }
+
+  # TODO: enable UintSlice
+  # UintSlice: {}
+  # TODO: enable Uint64Slice once #1334 lands
+  # Uint64Slice: {}

flag.go

@@ -5,7 +5,6 @@ import (
 	"flag"
 	"fmt"
 	"io/ioutil"
-	"reflect"
 	"regexp"
 	"runtime"
 	"strconv"
@@ -117,6 +116,12 @@ type DocGenerationFlag interface {
 	// GetValue returns the flags value as string representation and an empty
 	// string if the flag takes no value at all.
 	GetValue() string
+
+	// GetDefaultText returns the default text for this flag
+	GetDefaultText() string
+
+	// GetEnvVars returns the env vars for this flag
+	GetEnvVars() []string
 }
 
 // VisibleFlag is an interface that allows to check if a flag is visible
@@ -127,6 +132,14 @@ type VisibleFlag interface {
 	IsVisible() bool
 }
 
+// CategorizableFlag is an interface that allows us to potentially
+// use a flag in a categorized representation.
+type CategorizableFlag interface {
+	VisibleFlag
+
+	GetCategory() string
+}
+
 func flagSet(name string, flags []Flag) (*flag.FlagSet, error) {
 	set := flag.NewFlagSet(name, flag.ContinueOnError)
 
@@ -238,7 +251,7 @@ func prefixedNames(names []string, placeholder string) string {
 
 func withEnvHint(envVars []string, str string) string {
 	envText := ""
-	if envVars != nil && len(envVars) > 0 {
+	if len(envVars) > 0 {
 		prefix := "$"
 		suffix := ""
 		sep := ", $"
@@ -253,7 +266,7 @@ func withEnvHint(envVars []string, str string) string {
 	return str + envText
 }
 
-func flagNames(name string, aliases []string) []string {
+func FlagNames(name string, aliases []string) []string {
 	var ret []string
 
 	for _, part := range append([]string{name}, aliases...) {
@@ -267,17 +280,6 @@ func flagNames(name string, aliases []string) []string {
 	return ret
 }
 
-func flagStringSliceField(f Flag, name string) []string {
-	fv := flagValue(f)
-	field := fv.FieldByName(name)
-
-	if field.IsValid() {
-		return field.Interface().([]string)
-	}
-
-	return []string{}
-}
-
 func withFileHint(filePath, str string) string {
 	fileText := ""
 	if filePath != "" {
@@ -286,68 +288,34 @@ func withFileHint(filePath, str string) string {
 	return str + fileText
 }
 
-func flagValue(f Flag) reflect.Value {
-	fv := reflect.ValueOf(f)
-	for fv.Kind() == reflect.Ptr {
-		fv = reflect.Indirect(fv)
-	}
-	return fv
-}
-
 func formatDefault(format string) string {
 	return " (default: " + format + ")"
 }
 
 func stringifyFlag(f Flag) string {
-	fv := flagValue(f)
+	// enforce DocGeneration interface on flags to avoid reflection
-
+	df, ok := f.(DocGenerationFlag)
-	switch f := f.(type) {
+	if !ok {
-	case *IntSliceFlag:
+		return ""
-		return withEnvHint(flagStringSliceField(f, "EnvVars"),
-			stringifyIntSliceFlag(f))
-	case *Int64SliceFlag:
-		return withEnvHint(flagStringSliceField(f, "EnvVars"),
-			stringifyInt64SliceFlag(f))
-	case *Float64SliceFlag:
-		return withEnvHint(flagStringSliceField(f, "EnvVars"),
-			stringifyFloat64SliceFlag(f))
-	case *StringSliceFlag:
-		return withEnvHint(flagStringSliceField(f, "EnvVars"),
-			stringifyStringSliceFlag(f))
 	}
 
-	placeholder, usage := unquoteUsage(fv.FieldByName("Usage").String())
+	placeholder, usage := unquoteUsage(df.GetUsage())
-
+	needsPlaceholder := df.TakesValue()
-	needsPlaceholder := false
-	defaultValueString := ""
-	val := fv.FieldByName("Value")
-	if val.IsValid() {
-		needsPlaceholder = val.Kind() != reflect.Bool
-		defaultValueString = fmt.Sprintf(formatDefault("%v"), val.Interface())
-
-		if val.Kind() == reflect.String && val.String() != "" {
-			defaultValueString = fmt.Sprintf(formatDefault("%q"), val.String())
-		}
-	}
-
-	helpText := fv.FieldByName("DefaultText")
-	if helpText.IsValid() && helpText.String() != "" {
-		needsPlaceholder = val.Kind() != reflect.Bool
-		defaultValueString = fmt.Sprintf(formatDefault("%s"), helpText.String())
-	}
-
-	if defaultValueString == formatDefault("") {
-		defaultValueString = ""
-	}
 
 	if needsPlaceholder && placeholder == "" {
 		placeholder = defaultPlaceholder
 	}
 
+	defaultValueString := ""
+
+	if s := df.GetDefaultText(); s != "" {
+		defaultValueString = fmt.Sprintf(formatDefault("%s"), s)
+	}
+
 	usageWithDefault := strings.TrimSpace(usage + defaultValueString)
 
-	return withEnvHint(flagStringSliceField(f, "EnvVars"),
+	return withEnvHint(df.GetEnvVars(),
-		fmt.Sprintf("%s\t%s", prefixedNames(f.Names(), placeholder), usageWithDefault))
+		fmt.Sprintf("%s\t%s", prefixedNames(df.Names(), placeholder), usageWithDefault))
 }
 
 func stringifyIntSliceFlag(f *IntSliceFlag) string {
@@ -426,19 +394,26 @@ func hasFlag(flags []Flag, fl Flag) bool {
 	return false
 }
 
-func flagFromEnvOrFile(envVars []string, filePath string) (val string, ok bool) {
+// Return the first value from a list of environment variables and files
+// (which may or may not exist), a description of where the value was found,
+// and a boolean which is true if a value was found.
+func flagFromEnvOrFile(envVars []string, filePath string) (value string, fromWhere string, found bool) {
 	for _, envVar := range envVars {
 		envVar = strings.TrimSpace(envVar)
-		if val, ok := syscall.Getenv(envVar); ok {
+		if value, found := syscall.Getenv(envVar); found {
-			return val, true
+			return value, fmt.Sprintf("environment variable %q", envVar), true
 		}
 	}
 	for _, fileVar := range strings.Split(filePath, ",") {
 		if fileVar != "" {
 			if data, err := ioutil.ReadFile(fileVar); err == nil {
-				return string(data), true
+				return string(data), fmt.Sprintf("file %q", filePath), true
 			}
 		}
 	}
-	return "", false
+	return "", "", false
+}
+
+func flagSplitMultiValues(val string) []string {
+	return strings.Split(val, ",")
 }

flag_bool.go

@@ -6,42 +6,6 @@ import (
 	"strconv"
 )
 
-// BoolFlag is a flag with type bool
-type BoolFlag struct {
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	Value       bool
-	DefaultText string
-	Destination *bool
-	HasBeenSet  bool
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *BoolFlag) IsSet() bool {
-	return f.HasBeenSet
-}
-
-// String returns a readable representation of this value
-// (for usage defaults)
-func (f *BoolFlag) String() string {
-	return FlagStringer(f)
-}
-
-// Names returns the names of the flag
-func (f *BoolFlag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *BoolFlag) IsRequired() bool {
-	return f.Required
-}
-
 // TakesValue returns true of the flag takes a value, otherwise false
 func (f *BoolFlag) TakesValue() bool {
 	return false
@@ -52,25 +16,38 @@ func (f *BoolFlag) GetUsage() string {
 	return f.Usage
 }
 
+// GetCategory returns the category for the flag
+func (f *BoolFlag) GetCategory() string {
+	return f.Category
+}
+
 // GetValue returns the flags value as string representation and an empty
 // string if the flag takes no value at all.
 func (f *BoolFlag) GetValue() string {
 	return ""
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetDefaultText returns the default text for this flag
-func (f *BoolFlag) IsVisible() bool {
+func (f *BoolFlag) GetDefaultText() string {
-	return !f.Hidden
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	return fmt.Sprintf("%v", f.Value)
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *BoolFlag) GetEnvVars() []string {
+	return f.EnvVars
 }
 
 // Apply populates the flag given the flag set and environment
 func (f *BoolFlag) Apply(set *flag.FlagSet) error {
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
 		if val != "" {
 			valBool, err := strconv.ParseBool(val)
 
 			if err != nil {
-				return fmt.Errorf("could not parse %q as bool value for flag %s: %s", val, f.Name, err)
+				return fmt.Errorf("could not parse %q as bool value from %s for flag %s: %s", val, source, f.Name, err)
 			}
 
 			f.Value = valBool
@@ -89,10 +66,15 @@ func (f *BoolFlag) Apply(set *flag.FlagSet) error {
 	return nil
 }
 
+// Get returns the flag’s value in the given Context.
+func (f *BoolFlag) Get(ctx *Context) bool {
+	return ctx.Bool(f.Name)
+}
+
 // Bool looks up the value of a local BoolFlag, returns
 // false if not found
-func (c *Context) Bool(name string) bool {
+func (cCtx *Context) Bool(name string) bool {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupBool(name, fs)
 	}
 	return false

flag_duration.go

@@ -6,42 +6,6 @@ import (
 	"time"
 )
 
-// DurationFlag is a flag with type time.Duration (see https://golang.org/pkg/time/#ParseDuration)
-type DurationFlag struct {
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	Value       time.Duration
-	DefaultText string
-	Destination *time.Duration
-	HasBeenSet  bool
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *DurationFlag) IsSet() bool {
-	return f.HasBeenSet
-}
-
-// String returns a readable representation of this value
-// (for usage defaults)
-func (f *DurationFlag) String() string {
-	return FlagStringer(f)
-}
-
-// Names returns the names of the flag
-func (f *DurationFlag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *DurationFlag) IsRequired() bool {
-	return f.Required
-}
-
 // TakesValue returns true of the flag takes a value, otherwise false
 func (f *DurationFlag) TakesValue() bool {
 	return true
@@ -52,25 +16,38 @@ func (f *DurationFlag) GetUsage() string {
 	return f.Usage
 }
 
+// GetCategory returns the category for the flag
+func (f *DurationFlag) GetCategory() string {
+	return f.Category
+}
+
 // GetValue returns the flags value as string representation and an empty
 // string if the flag takes no value at all.
 func (f *DurationFlag) GetValue() string {
 	return f.Value.String()
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetDefaultText returns the default text for this flag
-func (f *DurationFlag) IsVisible() bool {
+func (f *DurationFlag) GetDefaultText() string {
-	return !f.Hidden
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	return f.GetValue()
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *DurationFlag) GetEnvVars() []string {
+	return f.EnvVars
 }
 
 // Apply populates the flag given the flag set and environment
 func (f *DurationFlag) Apply(set *flag.FlagSet) error {
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
 		if val != "" {
 			valDuration, err := time.ParseDuration(val)
 
 			if err != nil {
-				return fmt.Errorf("could not parse %q as duration value for flag %s: %s", val, f.Name, err)
+				return fmt.Errorf("could not parse %q as duration value from %s for flag %s: %s", val, source, f.Name, err)
 			}
 
 			f.Value = valDuration
@@ -88,10 +65,15 @@ func (f *DurationFlag) Apply(set *flag.FlagSet) error {
 	return nil
 }
 
+// Get returns the flag’s value in the given Context.
+func (f *DurationFlag) Get(ctx *Context) time.Duration {
+	return ctx.Duration(f.Name)
+}
+
 // Duration looks up the value of a local DurationFlag, returns
 // 0 if not found
-func (c *Context) Duration(name string) time.Duration {
+func (cCtx *Context) Duration(name string) time.Duration {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupDuration(name, fs)
 	}
 	return 0

flag_float64.go

@@ -6,42 +6,6 @@ import (
 	"strconv"
 )
 
-// Float64Flag is a flag with type float64
-type Float64Flag struct {
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	Value       float64
-	DefaultText string
-	Destination *float64
-	HasBeenSet  bool
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *Float64Flag) IsSet() bool {
-	return f.HasBeenSet
-}
-
-// String returns a readable representation of this value
-// (for usage defaults)
-func (f *Float64Flag) String() string {
-	return FlagStringer(f)
-}
-
-// Names returns the names of the flag
-func (f *Float64Flag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *Float64Flag) IsRequired() bool {
-	return f.Required
-}
-
 // TakesValue returns true of the flag takes a value, otherwise false
 func (f *Float64Flag) TakesValue() bool {
 	return true
@@ -52,24 +16,37 @@ func (f *Float64Flag) GetUsage() string {
 	return f.Usage
 }
 
+// GetCategory returns the category for the flag
+func (f *Float64Flag) GetCategory() string {
+	return f.Category
+}
+
 // GetValue returns the flags value as string representation and an empty
 // string if the flag takes no value at all.
 func (f *Float64Flag) GetValue() string {
-	return fmt.Sprintf("%f", f.Value)
+	return fmt.Sprintf("%v", f.Value)
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetDefaultText returns the default text for this flag
-func (f *Float64Flag) IsVisible() bool {
+func (f *Float64Flag) GetDefaultText() string {
-	return !f.Hidden
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	return f.GetValue()
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *Float64Flag) GetEnvVars() []string {
+	return f.EnvVars
 }
 
 // Apply populates the flag given the flag set and environment
 func (f *Float64Flag) Apply(set *flag.FlagSet) error {
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
 		if val != "" {
 			valFloat, err := strconv.ParseFloat(val, 64)
 			if err != nil {
-				return fmt.Errorf("could not parse %q as float64 value for flag %s: %s", val, f.Name, err)
+				return fmt.Errorf("could not parse %q as float64 value from %s for flag %s: %s", val, source, f.Name, err)
 			}
 
 			f.Value = valFloat
@@ -88,10 +65,15 @@ func (f *Float64Flag) Apply(set *flag.FlagSet) error {
 	return nil
 }
 
+// Get returns the flag’s value in the given Context.
+func (f *Float64Flag) Get(ctx *Context) float64 {
+	return ctx.Float64(f.Name)
+}
+
 // Float64 looks up the value of a local Float64Flag, returns
 // 0 if not found
-func (c *Context) Float64(name string) float64 {
+func (cCtx *Context) Float64(name string) float64 {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupFloat64(name, fs)
 	}
 	return 0

flag_float64_slice.go

@@ -43,18 +43,25 @@ func (f *Float64Slice) Set(value string) error {
 		return nil
 	}
 
-	tmp, err := strconv.ParseFloat(value, 64)
+	for _, s := range flagSplitMultiValues(value) {
-	if err != nil {
+		tmp, err := strconv.ParseFloat(strings.TrimSpace(s), 64)
-		return err
+		if err != nil {
-	}
+			return err
+		}
 
-	f.slice = append(f.slice, tmp)
+		f.slice = append(f.slice, tmp)
+	}
 	return nil
 }
 
 // String returns a readable representation of this value (for usage defaults)
 func (f *Float64Slice) String() string {
-	return fmt.Sprintf("%#v", f.slice)
+	v := f.slice
+	if v == nil {
+		// treat nil the same as zero length non-nil
+		v = make([]float64, 0)
+	}
+	return fmt.Sprintf("%#v", v)
 }
 
 // Serialize allows Float64Slice to fulfill Serializer
@@ -73,39 +80,10 @@ func (f *Float64Slice) Get() interface{} {
 	return *f
 }
 
-// Float64SliceFlag is a flag with type *Float64Slice
-type Float64SliceFlag struct {
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	Value       *Float64Slice
-	DefaultText string
-	HasBeenSet  bool
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *Float64SliceFlag) IsSet() bool {
-	return f.HasBeenSet
-}
-
 // String returns a readable representation of this value
 // (for usage defaults)
 func (f *Float64SliceFlag) String() string {
-	return FlagStringer(f)
+	return withEnvHint(f.GetEnvVars(), stringifyFloat64SliceFlag(f))
-}
-
-// Names returns the names of the flag
-func (f *Float64SliceFlag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *Float64SliceFlag) IsRequired() bool {
-	return f.Required
 }
 
 // TakesValue returns true if the flag takes a value, otherwise false
@@ -118,6 +96,11 @@ func (f *Float64SliceFlag) GetUsage() string {
 	return f.Usage
 }
 
+// GetCategory returns the category for the flag
+func (f *Float64SliceFlag) GetCategory() string {
+	return f.Category
+}
+
 // GetValue returns the flags value as string representation and an empty
 // string if the flag takes no value at all.
 func (f *Float64SliceFlag) GetValue() string {
@@ -127,45 +110,69 @@ func (f *Float64SliceFlag) GetValue() string {
 	return ""
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetDefaultText returns the default text for this flag
-func (f *Float64SliceFlag) IsVisible() bool {
+func (f *Float64SliceFlag) GetDefaultText() string {
-	return !f.Hidden
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	return f.GetValue()
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *Float64SliceFlag) GetEnvVars() []string {
+	return f.EnvVars
 }
 
 // Apply populates the flag given the flag set and environment
 func (f *Float64SliceFlag) Apply(set *flag.FlagSet) error {
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	// apply any default
-		if val != "" {
+	if f.Destination != nil && f.Value != nil {
-			f.Value = &Float64Slice{}
+		f.Destination.slice = make([]float64, len(f.Value.slice))
+		copy(f.Destination.slice, f.Value.slice)
+	}
 
-			for _, s := range strings.Split(val, ",") {
+	// resolve setValue (what we will assign to the set)
-				if err := f.Value.Set(strings.TrimSpace(s)); err != nil {
+	var setValue *Float64Slice
-					return fmt.Errorf("could not parse %q as float64 slice value for flag %s: %s", f.Value, f.Name, err)
+	switch {
+	case f.Destination != nil:
+		setValue = f.Destination
+	case f.Value != nil:
+		setValue = f.Value.clone()
+	default:
+		setValue = new(Float64Slice)
+	}
+
+	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
+		if val != "" {
+			for _, s := range flagSplitMultiValues(val) {
+				if err := setValue.Set(strings.TrimSpace(s)); err != nil {
+					return fmt.Errorf("could not parse %q as float64 slice value from %s for flag %s: %s", val, source, f.Name, err)
 				}
 			}
 
 			// Set this to false so that we reset the slice if we then set values from
 			// flags that have already been set by the environment.
-			f.Value.hasBeenSet = false
+			setValue.hasBeenSet = false
 			f.HasBeenSet = true
 		}
 	}
 
-	if f.Value == nil {
-		f.Value = &Float64Slice{}
-	}
-	copyValue := f.Value.clone()
 	for _, name := range f.Names() {
-		set.Var(copyValue, name, f.Usage)
+		set.Var(setValue, name, f.Usage)
 	}
 
 	return nil
 }
 
+// Get returns the flag’s value in the given Context.
+func (f *Float64SliceFlag) Get(ctx *Context) []float64 {
+	return ctx.Float64Slice(f.Name)
+}
+
 // Float64Slice looks up the value of a local Float64SliceFlag, returns
 // nil if not found
-func (c *Context) Float64Slice(name string) []float64 {
+func (cCtx *Context) Float64Slice(name string) []float64 {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupFloat64Slice(name, fs)
 	}
 	return nil
@@ -174,7 +181,7 @@ func (c *Context) Float64Slice(name string) []float64 {
 func lookupFloat64Slice(name string, set *flag.FlagSet) []float64 {
 	f := set.Lookup(name)
 	if f != nil {
-		if slice, ok := f.Value.(*Float64Slice); ok {
+		if slice, ok := unwrapFlagValue(f.Value).(*Float64Slice); ok {
 			return slice.Value()
 		}
 	}

flag_generic.go

@@ -11,42 +11,6 @@ type Generic interface {
 	String() string
 }
 
-// GenericFlag is a flag with type Generic
-type GenericFlag struct {
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	TakesFile   bool
-	Value       Generic
-	DefaultText string
-	HasBeenSet  bool
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *GenericFlag) IsSet() bool {
-	return f.HasBeenSet
-}
-
-// String returns a readable representation of this value
-// (for usage defaults)
-func (f *GenericFlag) String() string {
-	return FlagStringer(f)
-}
-
-// Names returns the names of the flag
-func (f *GenericFlag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *GenericFlag) IsRequired() bool {
-	return f.Required
-}
-
 // TakesValue returns true of the flag takes a value, otherwise false
 func (f *GenericFlag) TakesValue() bool {
 	return true
@@ -57,6 +21,11 @@ func (f *GenericFlag) GetUsage() string {
 	return f.Usage
 }
 
+// GetCategory returns the category for the flag
+func (f *GenericFlag) GetCategory() string {
+	return f.Category
+}
+
 // GetValue returns the flags value as string representation and an empty
 // string if the flag takes no value at all.
 func (f *GenericFlag) GetValue() string {
@@ -66,18 +35,26 @@ func (f *GenericFlag) GetValue() string {
 	return ""
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetDefaultText returns the default text for this flag
-func (f *GenericFlag) IsVisible() bool {
+func (f *GenericFlag) GetDefaultText() string {
-	return !f.Hidden
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	return f.GetValue()
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *GenericFlag) GetEnvVars() []string {
+	return f.EnvVars
 }
 
 // Apply takes the flagset and calls Set on the generic flag with the value
 // provided by the user for parsing by the flag
 func (f GenericFlag) Apply(set *flag.FlagSet) error {
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
 		if val != "" {
 			if err := f.Value.Set(val); err != nil {
-				return fmt.Errorf("could not parse %q as value for flag %s: %s", val, f.Name, err)
+				return fmt.Errorf("could not parse %q from %s as value for flag %s: %s", val, source, f.Name, err)
 			}
 
 			f.HasBeenSet = true
@@ -91,10 +68,15 @@ func (f GenericFlag) Apply(set *flag.FlagSet) error {
 	return nil
 }
 
+// Get returns the flag’s value in the given Context.
+func (f *GenericFlag) Get(ctx *Context) interface{} {
+	return ctx.Generic(f.Name)
+}
+
 // Generic looks up the value of a local GenericFlag, returns
 // nil if not found
-func (c *Context) Generic(name string) interface{} {
+func (cCtx *Context) Generic(name string) interface{} {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupGeneric(name, fs)
 	}
 	return nil

flag_int.go

@@ -6,42 +6,6 @@ import (
 	"strconv"
 )
 
-// IntFlag is a flag with type int
-type IntFlag struct {
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	Value       int
-	DefaultText string
-	Destination *int
-	HasBeenSet  bool
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *IntFlag) IsSet() bool {
-	return f.HasBeenSet
-}
-
-// String returns a readable representation of this value
-// (for usage defaults)
-func (f *IntFlag) String() string {
-	return FlagStringer(f)
-}
-
-// Names returns the names of the flag
-func (f *IntFlag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *IntFlag) IsRequired() bool {
-	return f.Required
-}
-
 // TakesValue returns true of the flag takes a value, otherwise false
 func (f *IntFlag) TakesValue() bool {
 	return true
@@ -52,25 +16,38 @@ func (f *IntFlag) GetUsage() string {
 	return f.Usage
 }
 
+// GetCategory returns the category for the flag
+func (f *IntFlag) GetCategory() string {
+	return f.Category
+}
+
 // GetValue returns the flags value as string representation and an empty
 // string if the flag takes no value at all.
 func (f *IntFlag) GetValue() string {
 	return fmt.Sprintf("%d", f.Value)
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetDefaultText returns the default text for this flag
-func (f *IntFlag) IsVisible() bool {
+func (f *IntFlag) GetDefaultText() string {
-	return !f.Hidden
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	return f.GetValue()
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *IntFlag) GetEnvVars() []string {
+	return f.EnvVars
 }
 
 // Apply populates the flag given the flag set and environment
 func (f *IntFlag) Apply(set *flag.FlagSet) error {
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
 		if val != "" {
 			valInt, err := strconv.ParseInt(val, 0, 64)
 
 			if err != nil {
-				return fmt.Errorf("could not parse %q as int value for flag %s: %s", val, f.Name, err)
+				return fmt.Errorf("could not parse %q as int value from %s for flag %s: %s", val, source, f.Name, err)
 			}
 
 			f.Value = int(valInt)
@@ -89,10 +66,15 @@ func (f *IntFlag) Apply(set *flag.FlagSet) error {
 	return nil
 }
 
+// Get returns the flag’s value in the given Context.
+func (f *IntFlag) Get(ctx *Context) int {
+	return ctx.Int(f.Name)
+}
+
 // Int looks up the value of a local IntFlag, returns
 // 0 if not found
-func (c *Context) Int(name string) int {
+func (cCtx *Context) Int(name string) int {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupInt(name, fs)
 	}
 	return 0

flag_int64.go

@@ -6,42 +6,6 @@ import (
 	"strconv"
 )
 
-// Int64Flag is a flag with type int64
-type Int64Flag struct {
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	Value       int64
-	DefaultText string
-	Destination *int64
-	HasBeenSet  bool
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *Int64Flag) IsSet() bool {
-	return f.HasBeenSet
-}
-
-// String returns a readable representation of this value
-// (for usage defaults)
-func (f *Int64Flag) String() string {
-	return FlagStringer(f)
-}
-
-// Names returns the names of the flag
-func (f *Int64Flag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *Int64Flag) IsRequired() bool {
-	return f.Required
-}
-
 // TakesValue returns true of the flag takes a value, otherwise false
 func (f *Int64Flag) TakesValue() bool {
 	return true
@@ -52,25 +16,38 @@ func (f *Int64Flag) GetUsage() string {
 	return f.Usage
 }
 
+// GetCategory returns the category for the flag
+func (f *Int64Flag) GetCategory() string {
+	return f.Category
+}
+
 // GetValue returns the flags value as string representation and an empty
 // string if the flag takes no value at all.
 func (f *Int64Flag) GetValue() string {
 	return fmt.Sprintf("%d", f.Value)
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetDefaultText returns the default text for this flag
-func (f *Int64Flag) IsVisible() bool {
+func (f *Int64Flag) GetDefaultText() string {
-	return !f.Hidden
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	return f.GetValue()
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *Int64Flag) GetEnvVars() []string {
+	return f.EnvVars
 }
 
 // Apply populates the flag given the flag set and environment
 func (f *Int64Flag) Apply(set *flag.FlagSet) error {
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
 		if val != "" {
 			valInt, err := strconv.ParseInt(val, 0, 64)
 
 			if err != nil {
-				return fmt.Errorf("could not parse %q as int value for flag %s: %s", val, f.Name, err)
+				return fmt.Errorf("could not parse %q as int value from %s for flag %s: %s", val, source, f.Name, err)
 			}
 
 			f.Value = valInt
@@ -88,10 +65,15 @@ func (f *Int64Flag) Apply(set *flag.FlagSet) error {
 	return nil
 }
 
+// Get returns the flag’s value in the given Context.
+func (f *Int64Flag) Get(ctx *Context) int64 {
+	return ctx.Int64(f.Name)
+}
+
 // Int64 looks up the value of a local Int64Flag, returns
 // 0 if not found
-func (c *Context) Int64(name string) int64 {
+func (cCtx *Context) Int64(name string) int64 {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupInt64(name, fs)
 	}
 	return 0

flag_int64_slice.go

@@ -43,19 +43,26 @@ func (i *Int64Slice) Set(value string) error {
 		return nil
 	}
 
-	tmp, err := strconv.ParseInt(value, 0, 64)
+	for _, s := range flagSplitMultiValues(value) {
-	if err != nil {
+		tmp, err := strconv.ParseInt(strings.TrimSpace(s), 0, 64)
-		return err
+		if err != nil {
-	}
+			return err
+		}
 
-	i.slice = append(i.slice, tmp)
+		i.slice = append(i.slice, tmp)
+	}
 
 	return nil
 }
 
 // String returns a readable representation of this value (for usage defaults)
 func (i *Int64Slice) String() string {
-	return fmt.Sprintf("%#v", i.slice)
+	v := i.slice
+	if v == nil {
+		// treat nil the same as zero length non-nil
+		v = make([]int64, 0)
+	}
+	return fmt.Sprintf("%#v", v)
 }
 
 // Serialize allows Int64Slice to fulfill Serializer
@@ -74,39 +81,10 @@ func (i *Int64Slice) Get() interface{} {
 	return *i
 }
 
-// Int64SliceFlag is a flag with type *Int64Slice
-type Int64SliceFlag struct {
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	Value       *Int64Slice
-	DefaultText string
-	HasBeenSet  bool
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *Int64SliceFlag) IsSet() bool {
-	return f.HasBeenSet
-}
-
 // String returns a readable representation of this value
 // (for usage defaults)
 func (f *Int64SliceFlag) String() string {
-	return FlagStringer(f)
+	return withEnvHint(f.GetEnvVars(), stringifyInt64SliceFlag(f))
-}
-
-// Names returns the names of the flag
-func (f *Int64SliceFlag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *Int64SliceFlag) IsRequired() bool {
-	return f.Required
 }
 
 // TakesValue returns true of the flag takes a value, otherwise false
@@ -115,10 +93,15 @@ func (f *Int64SliceFlag) TakesValue() bool {
 }
 
 // GetUsage returns the usage string for the flag
-func (f Int64SliceFlag) GetUsage() string {
+func (f *Int64SliceFlag) GetUsage() string {
 	return f.Usage
 }
 
+// GetCategory returns the category for the flag
+func (f *Int64SliceFlag) GetCategory() string {
+	return f.Category
+}
+
 // GetValue returns the flags value as string representation and an empty
 // string if the flag takes no value at all.
 func (f *Int64SliceFlag) GetValue() string {
@@ -128,43 +111,67 @@ func (f *Int64SliceFlag) GetValue() string {
 	return ""
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetDefaultText returns the default text for this flag
-func (f *Int64SliceFlag) IsVisible() bool {
+func (f *Int64SliceFlag) GetDefaultText() string {
-	return !f.Hidden
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	return f.GetValue()
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *Int64SliceFlag) GetEnvVars() []string {
+	return f.EnvVars
 }
 
 // Apply populates the flag given the flag set and environment
 func (f *Int64SliceFlag) Apply(set *flag.FlagSet) error {
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	// apply any default
-		f.Value = &Int64Slice{}
+	if f.Destination != nil && f.Value != nil {
+		f.Destination.slice = make([]int64, len(f.Value.slice))
+		copy(f.Destination.slice, f.Value.slice)
+	}
 
-		for _, s := range strings.Split(val, ",") {
+	// resolve setValue (what we will assign to the set)
-			if err := f.Value.Set(strings.TrimSpace(s)); err != nil {
+	var setValue *Int64Slice
-				return fmt.Errorf("could not parse %q as int64 slice value for flag %s: %s", val, f.Name, err)
+	switch {
+	case f.Destination != nil:
+		setValue = f.Destination
+	case f.Value != nil:
+		setValue = f.Value.clone()
+	default:
+		setValue = new(Int64Slice)
+	}
+
+	if val, source, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok && val != "" {
+		for _, s := range flagSplitMultiValues(val) {
+			if err := setValue.Set(strings.TrimSpace(s)); err != nil {
+				return fmt.Errorf("could not parse %q as int64 slice value from %s for flag %s: %s", val, source, f.Name, err)
 			}
 		}
 
 		// Set this to false so that we reset the slice if we then set values from
 		// flags that have already been set by the environment.
-		f.Value.hasBeenSet = false
+		setValue.hasBeenSet = false
 		f.HasBeenSet = true
 	}
 
-	if f.Value == nil {
-		f.Value = &Int64Slice{}
-	}
-	copyValue := f.Value.clone()
 	for _, name := range f.Names() {
-		set.Var(copyValue, name, f.Usage)
+		set.Var(setValue, name, f.Usage)
 	}
 
 	return nil
 }
 
+// Get returns the flag’s value in the given Context.
+func (f *Int64SliceFlag) Get(ctx *Context) []int64 {
+	return ctx.Int64Slice(f.Name)
+}
+
 // Int64Slice looks up the value of a local Int64SliceFlag, returns
 // nil if not found
-func (c *Context) Int64Slice(name string) []int64 {
+func (cCtx *Context) Int64Slice(name string) []int64 {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupInt64Slice(name, fs)
 	}
 	return nil
@@ -173,7 +180,7 @@ func (c *Context) Int64Slice(name string) []int64 {
 func lookupInt64Slice(name string, set *flag.FlagSet) []int64 {
 	f := set.Lookup(name)
 	if f != nil {
-		if slice, ok := f.Value.(*Int64Slice); ok {
+		if slice, ok := unwrapFlagValue(f.Value).(*Int64Slice); ok {
 			return slice.Value()
 		}
 	}

flag_int_slice.go

@@ -54,19 +54,26 @@ func (i *IntSlice) Set(value string) error {
 		return nil
 	}
 
-	tmp, err := strconv.ParseInt(value, 0, 64)
+	for _, s := range flagSplitMultiValues(value) {
-	if err != nil {
+		tmp, err := strconv.ParseInt(strings.TrimSpace(s), 0, 64)
-		return err
+		if err != nil {
-	}
+			return err
+		}
 
-	i.slice = append(i.slice, int(tmp))
+		i.slice = append(i.slice, int(tmp))
+	}
 
 	return nil
 }
 
 // String returns a readable representation of this value (for usage defaults)
 func (i *IntSlice) String() string {
-	return fmt.Sprintf("%#v", i.slice)
+	v := i.slice
+	if v == nil {
+		// treat nil the same as zero length non-nil
+		v = make([]int, 0)
+	}
+	return fmt.Sprintf("%#v", v)
 }
 
 // Serialize allows IntSlice to fulfill Serializer
@@ -85,39 +92,10 @@ func (i *IntSlice) Get() interface{} {
 	return *i
 }
 
-// IntSliceFlag is a flag with type *IntSlice
-type IntSliceFlag struct {
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	Value       *IntSlice
-	DefaultText string
-	HasBeenSet  bool
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *IntSliceFlag) IsSet() bool {
-	return f.HasBeenSet
-}
-
 // String returns a readable representation of this value
 // (for usage defaults)
 func (f *IntSliceFlag) String() string {
-	return FlagStringer(f)
+	return withEnvHint(f.GetEnvVars(), stringifyIntSliceFlag(f))
-}
-
-// Names returns the names of the flag
-func (f *IntSliceFlag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *IntSliceFlag) IsRequired() bool {
-	return f.Required
 }
 
 // TakesValue returns true of the flag takes a value, otherwise false
@@ -126,10 +104,15 @@ func (f *IntSliceFlag) TakesValue() bool {
 }
 
 // GetUsage returns the usage string for the flag
-func (f IntSliceFlag) GetUsage() string {
+func (f *IntSliceFlag) GetUsage() string {
 	return f.Usage
 }
 
+// GetCategory returns the category for the flag
+func (f *IntSliceFlag) GetCategory() string {
+	return f.Category
+}
+
 // GetValue returns the flags value as string representation and an empty
 // string if the flag takes no value at all.
 func (f *IntSliceFlag) GetValue() string {
@@ -139,43 +122,67 @@ func (f *IntSliceFlag) GetValue() string {
 	return ""
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetDefaultText returns the default text for this flag
-func (f *IntSliceFlag) IsVisible() bool {
+func (f *IntSliceFlag) GetDefaultText() string {
-	return !f.Hidden
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	return f.GetValue()
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *IntSliceFlag) GetEnvVars() []string {
+	return f.EnvVars
 }
 
 // Apply populates the flag given the flag set and environment
 func (f *IntSliceFlag) Apply(set *flag.FlagSet) error {
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	// apply any default
-		f.Value = &IntSlice{}
+	if f.Destination != nil && f.Value != nil {
+		f.Destination.slice = make([]int, len(f.Value.slice))
+		copy(f.Destination.slice, f.Value.slice)
+	}
 
-		for _, s := range strings.Split(val, ",") {
+	// resolve setValue (what we will assign to the set)
-			if err := f.Value.Set(strings.TrimSpace(s)); err != nil {
+	var setValue *IntSlice
-				return fmt.Errorf("could not parse %q as int slice value for flag %s: %s", val, f.Name, err)
+	switch {
+	case f.Destination != nil:
+		setValue = f.Destination
+	case f.Value != nil:
+		setValue = f.Value.clone()
+	default:
+		setValue = new(IntSlice)
+	}
+
+	if val, source, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok && val != "" {
+		for _, s := range flagSplitMultiValues(val) {
+			if err := setValue.Set(strings.TrimSpace(s)); err != nil {
+				return fmt.Errorf("could not parse %q as int slice value from %s for flag %s: %s", val, source, f.Name, err)
 			}
 		}
 
 		// Set this to false so that we reset the slice if we then set values from
 		// flags that have already been set by the environment.
-		f.Value.hasBeenSet = false
+		setValue.hasBeenSet = false
 		f.HasBeenSet = true
 	}
 
-	if f.Value == nil {
-		f.Value = &IntSlice{}
-	}
-	copyValue := f.Value.clone()
 	for _, name := range f.Names() {
-		set.Var(copyValue, name, f.Usage)
+		set.Var(setValue, name, f.Usage)
 	}
 
 	return nil
 }
 
+// Get returns the flag’s value in the given Context.
+func (f *IntSliceFlag) Get(ctx *Context) []int {
+	return ctx.IntSlice(f.Name)
+}
+
 // IntSlice looks up the value of a local IntSliceFlag, returns
 // nil if not found
-func (c *Context) IntSlice(name string) []int {
+func (cCtx *Context) IntSlice(name string) []int {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupIntSlice(name, fs)
 	}
 	return nil
@@ -184,7 +191,7 @@ func (c *Context) IntSlice(name string) []int {
 func lookupIntSlice(name string, set *flag.FlagSet) []int {
 	f := set.Lookup(name)
 	if f != nil {
-		if slice, ok := f.Value.(*IntSlice); ok {
+		if slice, ok := unwrapFlagValue(f.Value).(*IntSlice); ok {
 			return slice.Value()
 		}
 	}

flag_path.go

@@ -1,42 +1,11 @@
 package cli
 
-import "flag"
+import (
+	"flag"
+	"fmt"
+)
 
-type PathFlag struct {
+type Path = string
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	TakesFile   bool
-	Value       string
-	DefaultText string
-	Destination *string
-	HasBeenSet  bool
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *PathFlag) IsSet() bool {
-	return f.HasBeenSet
-}
-
-// String returns a readable representation of this value
-// (for usage defaults)
-func (f *PathFlag) String() string {
-	return FlagStringer(f)
-}
-
-// Names returns the names of the flag
-func (f *PathFlag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *PathFlag) IsRequired() bool {
-	return f.Required
-}
 
 // TakesValue returns true of the flag takes a value, otherwise false
 func (f *PathFlag) TakesValue() bool {
@@ -48,20 +17,36 @@ func (f *PathFlag) GetUsage() string {
 	return f.Usage
 }
 
+// GetCategory returns the category for the flag
+func (f *PathFlag) GetCategory() string {
+	return f.Category
+}
+
 // GetValue returns the flags value as string representation and an empty
 // string if the flag takes no value at all.
 func (f *PathFlag) GetValue() string {
 	return f.Value
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetDefaultText returns the default text for this flag
-func (f *PathFlag) IsVisible() bool {
+func (f *PathFlag) GetDefaultText() string {
-	return !f.Hidden
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	if f.Value == "" {
+		return f.Value
+	}
+	return fmt.Sprintf("%q", f.Value)
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *PathFlag) GetEnvVars() []string {
+	return f.EnvVars
 }
 
 // Apply populates the flag given the flag set and environment
 func (f *PathFlag) Apply(set *flag.FlagSet) error {
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	if val, _, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
 		f.Value = val
 		f.HasBeenSet = true
 	}
@@ -77,10 +62,15 @@ func (f *PathFlag) Apply(set *flag.FlagSet) error {
 	return nil
 }
 
+// Get returns the flag’s value in the given Context.
+func (f *PathFlag) Get(ctx *Context) string {
+	return ctx.Path(f.Name)
+}
+
 // Path looks up the value of a local PathFlag, returns
 // "" if not found
-func (c *Context) Path(name string) string {
+func (cCtx *Context) Path(name string) string {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupPath(name, fs)
 	}
 

flag_string.go

@@ -1,43 +1,9 @@
 package cli
 
-import "flag"
+import (
-
+	"flag"
-// StringFlag is a flag with type string
+	"fmt"
-type StringFlag struct {
+)
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	TakesFile   bool
-	Value       string
-	DefaultText string
-	Destination *string
-	HasBeenSet  bool
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *StringFlag) IsSet() bool {
-	return f.HasBeenSet
-}
-
-// String returns a readable representation of this value
-// (for usage defaults)
-func (f *StringFlag) String() string {
-	return FlagStringer(f)
-}
-
-// Names returns the names of the flag
-func (f *StringFlag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *StringFlag) IsRequired() bool {
-	return f.Required
-}
 
 // TakesValue returns true of the flag takes a value, otherwise false
 func (f *StringFlag) TakesValue() bool {
@@ -49,20 +15,36 @@ func (f *StringFlag) GetUsage() string {
 	return f.Usage
 }
 
+// GetCategory returns the category for the flag
+func (f *StringFlag) GetCategory() string {
+	return f.Category
+}
+
 // GetValue returns the flags value as string representation and an empty
 // string if the flag takes no value at all.
 func (f *StringFlag) GetValue() string {
 	return f.Value
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetDefaultText returns the default text for this flag
-func (f *StringFlag) IsVisible() bool {
+func (f *StringFlag) GetDefaultText() string {
-	return !f.Hidden
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	if f.Value == "" {
+		return f.Value
+	}
+	return fmt.Sprintf("%q", f.Value)
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *StringFlag) GetEnvVars() []string {
+	return f.EnvVars
 }
 
 // Apply populates the flag given the flag set and environment
 func (f *StringFlag) Apply(set *flag.FlagSet) error {
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	if val, _, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
 		f.Value = val
 		f.HasBeenSet = true
 	}
@@ -78,10 +60,15 @@ func (f *StringFlag) Apply(set *flag.FlagSet) error {
 	return nil
 }
 
+// Get returns the flag’s value in the given Context.
+func (f *StringFlag) Get(ctx *Context) string {
+	return ctx.String(f.Name)
+}
+
 // String looks up the value of a local StringFlag, returns
 // "" if not found
-func (c *Context) String(name string) string {
+func (cCtx *Context) String(name string) string {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupString(name, fs)
 	}
 	return ""

flag_string_slice.go

@@ -42,7 +42,9 @@ func (s *StringSlice) Set(value string) error {
 		return nil
 	}
 
-	s.slice = append(s.slice, value)
+	for _, t := range flagSplitMultiValues(value) {
+		s.slice = append(s.slice, strings.TrimSpace(t))
+	}
 
 	return nil
 }
@@ -68,41 +70,10 @@ func (s *StringSlice) Get() interface{} {
 	return *s
 }
 
-// StringSliceFlag is a flag with type *StringSlice
-type StringSliceFlag struct {
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	TakesFile   bool
-	Value       *StringSlice
-	DefaultText string
-	HasBeenSet  bool
-	Destination *StringSlice
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *StringSliceFlag) IsSet() bool {
-	return f.HasBeenSet
-}
-
 // String returns a readable representation of this value
 // (for usage defaults)
 func (f *StringSliceFlag) String() string {
-	return FlagStringer(f)
+	return withEnvHint(f.GetEnvVars(), stringifyStringSliceFlag(f))
-}
-
-// Names returns the names of the flag
-func (f *StringSliceFlag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *StringSliceFlag) IsRequired() bool {
-	return f.Required
 }
 
 // TakesValue returns true of the flag takes a value, otherwise false
@@ -115,6 +86,11 @@ func (f *StringSliceFlag) GetUsage() string {
 	return f.Usage
 }
 
+// GetCategory returns the category for the flag
+func (f *StringSliceFlag) GetCategory() string {
+	return f.Category
+}
+
 // GetValue returns the flags value as string representation and an empty
 // string if the flag takes no value at all.
 func (f *StringSliceFlag) GetValue() string {
@@ -124,48 +100,51 @@ func (f *StringSliceFlag) GetValue() string {
 	return ""
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetDefaultText returns the default text for this flag
-func (f *StringSliceFlag) IsVisible() bool {
+func (f *StringSliceFlag) GetDefaultText() string {
-	return !f.Hidden
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	return f.GetValue()
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *StringSliceFlag) GetEnvVars() []string {
+	return f.EnvVars
 }
 
 // Apply populates the flag given the flag set and environment
 func (f *StringSliceFlag) Apply(set *flag.FlagSet) error {
-
+	// apply any default
 	if f.Destination != nil && f.Value != nil {
 		f.Destination.slice = make([]string, len(f.Value.slice))
 		copy(f.Destination.slice, f.Value.slice)
-
 	}
 
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	// resolve setValue (what we will assign to the set)
-		if f.Value == nil {
+	var setValue *StringSlice
-			f.Value = &StringSlice{}
+	switch {
-		}
+	case f.Destination != nil:
-		destination := f.Value
+		setValue = f.Destination
-		if f.Destination != nil {
+	case f.Value != nil:
-			destination = f.Destination
+		setValue = f.Value.clone()
-		}
+	default:
+		setValue = new(StringSlice)
+	}
 
-		for _, s := range strings.Split(val, ",") {
+	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
-			if err := destination.Set(strings.TrimSpace(s)); err != nil {
+		for _, s := range flagSplitMultiValues(val) {
-				return fmt.Errorf("could not parse %q as string value for flag %s: %s", val, f.Name, err)
+			if err := setValue.Set(strings.TrimSpace(s)); err != nil {
+				return fmt.Errorf("could not parse %q as string value from %s for flag %s: %s", val, source, f.Name, err)
 			}
 		}
 
 		// Set this to false so that we reset the slice if we then set values from
 		// flags that have already been set by the environment.
-		destination.hasBeenSet = false
+		setValue.hasBeenSet = false
 		f.HasBeenSet = true
 	}
 
-	if f.Value == nil {
-		f.Value = &StringSlice{}
-	}
-	setValue := f.Destination
-	if f.Destination == nil {
-		setValue = f.Value.clone()
-	}
 	for _, name := range f.Names() {
 		set.Var(setValue, name, f.Usage)
 	}
@@ -173,10 +152,15 @@ func (f *StringSliceFlag) Apply(set *flag.FlagSet) error {
 	return nil
 }
 
+// Get returns the flag’s value in the given Context.
+func (f *StringSliceFlag) Get(ctx *Context) []string {
+	return ctx.StringSlice(f.Name)
+}
+
 // StringSlice looks up the value of a local StringSliceFlag, returns
 // nil if not found
-func (c *Context) StringSlice(name string) []string {
+func (cCtx *Context) StringSlice(name string) []string {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupStringSlice(name, fs)
 	}
 	return nil
@@ -185,7 +169,7 @@ func (c *Context) StringSlice(name string) []string {
 func lookupStringSlice(name string, set *flag.FlagSet) []string {
 	f := set.Lookup(name)
 	if f != nil {
-		if slice, ok := f.Value.(*StringSlice); ok {
+		if slice, ok := unwrapFlagValue(f.Value).(*StringSlice); ok {
 			return slice.Value()
 		}
 	}

flag_test.go

@@ -51,6 +51,17 @@ func TestBoolFlagApply_SetsAllNames(t *testing.T) {
 	expect(t, v, true)
 }
 
+func TestBoolFlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.Bool("trueflag", true, "doc")
+	set.Bool("falseflag", false, "doc")
+	ctx := NewContext(nil, set, nil)
+	tf := &BoolFlag{Name: "trueflag"}
+	ff := &BoolFlag{Name: "falseflag"}
+	expect(t, tf.Get(ctx), true)
+	expect(t, ff.Get(ctx), false)
+}
+
 func TestFlagsFromEnv(t *testing.T) {
 	newSetFloat64Slice := func(defaults ...float64) Float64Slice {
 		s := NewFloat64Slice(defaults...)
@@ -85,33 +96,33 @@ func TestFlagsFromEnv(t *testing.T) {
 		{"", false, &BoolFlag{Name: "debug", EnvVars: []string{"DEBUG"}}, ""},
 		{"1", true, &BoolFlag{Name: "debug", EnvVars: []string{"DEBUG"}}, ""},
 		{"false", false, &BoolFlag{Name: "debug", EnvVars: []string{"DEBUG"}}, ""},
-		{"foobar", true, &BoolFlag{Name: "debug", EnvVars: []string{"DEBUG"}}, `could not parse "foobar" as bool value for flag debug: .*`},
+		{"foobar", true, &BoolFlag{Name: "debug", EnvVars: []string{"DEBUG"}}, `could not parse "foobar" as bool value from environment variable "DEBUG" for flag debug: .*`},
 
 		{"1s", 1 * time.Second, &DurationFlag{Name: "time", EnvVars: []string{"TIME"}}, ""},
-		{"foobar", false, &DurationFlag{Name: "time", EnvVars: []string{"TIME"}}, `could not parse "foobar" as duration value for flag time: .*`},
+		{"foobar", false, &DurationFlag{Name: "time", EnvVars: []string{"TIME"}}, `could not parse "foobar" as duration value from environment variable "TIME" for flag time: .*`},
 
 		{"1.2", 1.2, &Float64Flag{Name: "seconds", EnvVars: []string{"SECONDS"}}, ""},
 		{"1", 1.0, &Float64Flag{Name: "seconds", EnvVars: []string{"SECONDS"}}, ""},
-		{"foobar", 0, &Float64Flag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as float64 value for flag seconds: .*`},
+		{"foobar", 0, &Float64Flag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as float64 value from environment variable "SECONDS" for flag seconds: .*`},
 
 		{"1", int64(1), &Int64Flag{Name: "seconds", EnvVars: []string{"SECONDS"}}, ""},
-		{"1.2", 0, &Int64Flag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "1.2" as int value for flag seconds: .*`},
+		{"1.2", 0, &Int64Flag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "1.2" as int value from environment variable "SECONDS" for flag seconds: .*`},
-		{"foobar", 0, &Int64Flag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as int value for flag seconds: .*`},
+		{"foobar", 0, &Int64Flag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as int value from environment variable "SECONDS" for flag seconds: .*`},
 
 		{"1", 1, &IntFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, ""},
-		{"1.2", 0, &IntFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "1.2" as int value for flag seconds: .*`},
+		{"1.2", 0, &IntFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "1.2" as int value from environment variable "SECONDS" for flag seconds: .*`},
-		{"foobar", 0, &IntFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as int value for flag seconds: .*`},
+		{"foobar", 0, &IntFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as int value from environment variable "SECONDS" for flag seconds: .*`},
 
 		{"1.0,2", newSetFloat64Slice(1, 2), &Float64SliceFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, ""},
-		{"foobar", newSetFloat64Slice(), &Float64SliceFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "\[\]float64{}" as float64 slice value for flag seconds: .*`},
+		{"foobar", newSetFloat64Slice(), &Float64SliceFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as float64 slice value from environment variable "SECONDS" for flag seconds: .*`},
 
 		{"1,2", newSetIntSlice(1, 2), &IntSliceFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, ""},
-		{"1.2,2", newSetIntSlice(), &IntSliceFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "1.2,2" as int slice value for flag seconds: .*`},
+		{"1.2,2", newSetIntSlice(), &IntSliceFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "1.2,2" as int slice value from environment variable "SECONDS" for flag seconds: .*`},
-		{"foobar", newSetIntSlice(), &IntSliceFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as int slice value for flag seconds: .*`},
+		{"foobar", newSetIntSlice(), &IntSliceFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as int slice value from environment variable "SECONDS" for flag seconds: .*`},
 
 		{"1,2", newSetInt64Slice(1, 2), &Int64SliceFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, ""},
-		{"1.2,2", newSetInt64Slice(), &Int64SliceFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "1.2,2" as int64 slice value for flag seconds: .*`},
+		{"1.2,2", newSetInt64Slice(), &Int64SliceFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "1.2,2" as int64 slice value from environment variable "SECONDS" for flag seconds: .*`},
-		{"foobar", newSetInt64Slice(), &Int64SliceFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as int64 slice value for flag seconds: .*`},
+		{"foobar", newSetInt64Slice(), &Int64SliceFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as int64 slice value from environment variable "SECONDS" for flag seconds: .*`},
 
 		{"foo", "foo", &StringFlag{Name: "name", EnvVars: []string{"NAME"}}, ""},
 		{"path", "path", &PathFlag{Name: "path", EnvVars: []string{"PATH"}}, ""},
@@ -119,12 +130,12 @@ func TestFlagsFromEnv(t *testing.T) {
 		{"foo,bar", newSetStringSlice("foo", "bar"), &StringSliceFlag{Name: "names", EnvVars: []string{"NAMES"}}, ""},
 
 		{"1", uint(1), &UintFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, ""},
-		{"1.2", 0, &UintFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "1.2" as uint value for flag seconds: .*`},
+		{"1.2", 0, &UintFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "1.2" as uint value from environment variable "SECONDS" for flag seconds: .*`},
-		{"foobar", 0, &UintFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as uint value for flag seconds: .*`},
+		{"foobar", 0, &UintFlag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as uint value from environment variable "SECONDS" for flag seconds: .*`},
 
 		{"1", uint64(1), &Uint64Flag{Name: "seconds", EnvVars: []string{"SECONDS"}}, ""},
-		{"1.2", 0, &Uint64Flag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "1.2" as uint64 value for flag seconds: .*`},
+		{"1.2", 0, &Uint64Flag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "1.2" as uint64 value from environment variable "SECONDS" for flag seconds: .*`},
-		{"foobar", 0, &Uint64Flag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as uint64 value for flag seconds: .*`},
+		{"foobar", 0, &Uint64Flag{Name: "seconds", EnvVars: []string{"SECONDS"}}, `could not parse "foobar" as uint64 value from environment variable "SECONDS" for flag seconds: .*`},
 
 		{"foo,bar", &Parser{"foo", "bar"}, &GenericFlag{Name: "names", Value: &Parser{}, EnvVars: []string{"NAMES"}}, ""},
 	}
@@ -132,8 +143,13 @@ func TestFlagsFromEnv(t *testing.T) {
 	for i, test := range flagTests {
 		defer resetEnv(os.Environ())
 		os.Clearenv()
-		envVarSlice := reflect.Indirect(reflect.ValueOf(test.flag)).FieldByName("EnvVars").Slice(0, 1)
+
-		_ = os.Setenv(envVarSlice.Index(0).String(), test.input)
+		f, ok := test.flag.(DocGenerationFlag)
+		if !ok {
+			t.Errorf("flag %v needs to implement DocGenerationFlag to retrieve env vars", test.flag)
+		}
+		envVarSlice := f.GetEnvVars()
+		_ = os.Setenv(envVarSlice[0], test.input)
 
 		a := App{
 			Flags: []Flag{test.flag},
@@ -163,6 +179,183 @@ func TestFlagsFromEnv(t *testing.T) {
 	}
 }
 
+type nodocFlag struct {
+	Flag
+
+	Name string
+}
+
+func TestFlagStringifying(t *testing.T) {
+	for _, tc := range []struct {
+		name     string
+		fl       Flag
+		expected string
+	}{
+		{
+			name:     "bool-flag",
+			fl:       &BoolFlag{Name: "vividly"},
+			expected: "--vividly\t(default: false)",
+		},
+		{
+			name:     "bool-flag-with-default-text",
+			fl:       &BoolFlag{Name: "wildly", DefaultText: "scrambled"},
+			expected: "--wildly\t(default: scrambled)",
+		},
+		{
+			name:     "duration-flag",
+			fl:       &DurationFlag{Name: "scream-for"},
+			expected: "--scream-for value\t(default: 0s)",
+		},
+		{
+			name:     "duration-flag-with-default-text",
+			fl:       &DurationFlag{Name: "feels-about", DefaultText: "whimsically"},
+			expected: "--feels-about value\t(default: whimsically)",
+		},
+		{
+			name:     "float64-flag",
+			fl:       &Float64Flag{Name: "arduous"},
+			expected: "--arduous value\t(default: 0)",
+		},
+		{
+			name:     "float64-flag-with-default-text",
+			fl:       &Float64Flag{Name: "filibuster", DefaultText: "42"},
+			expected: "--filibuster value\t(default: 42)",
+		},
+		{
+			name:     "float64-slice-flag",
+			fl:       &Float64SliceFlag{Name: "pizzas"},
+			expected: "--pizzas value\t",
+		},
+		{
+			name:     "float64-slice-flag-with-default-text",
+			fl:       &Float64SliceFlag{Name: "pepperonis", DefaultText: "shaved"},
+			expected: "--pepperonis value\t(default: shaved)",
+		},
+		{
+			name:     "generic-flag",
+			fl:       &GenericFlag{Name: "yogurt"},
+			expected: "--yogurt value\t",
+		},
+		{
+			name:     "generic-flag-with-default-text",
+			fl:       &GenericFlag{Name: "ricotta", DefaultText: "plops"},
+			expected: "--ricotta value\t(default: plops)",
+		},
+		{
+			name:     "int-flag",
+			fl:       &IntFlag{Name: "grubs"},
+			expected: "--grubs value\t(default: 0)",
+		},
+		{
+			name:     "int-flag-with-default-text",
+			fl:       &IntFlag{Name: "poisons", DefaultText: "11ty"},
+			expected: "--poisons value\t(default: 11ty)",
+		},
+		{
+			name:     "int-slice-flag",
+			fl:       &IntSliceFlag{Name: "pencils"},
+			expected: "--pencils value\t",
+		},
+		{
+			name:     "int-slice-flag-with-default-text",
+			fl:       &IntFlag{Name: "pens", DefaultText: "-19"},
+			expected: "--pens value\t(default: -19)",
+		},
+		{
+			name:     "int64-flag",
+			fl:       &Int64Flag{Name: "flume"},
+			expected: "--flume value\t(default: 0)",
+		},
+		{
+			name:     "int64-flag-with-default-text",
+			fl:       &Int64Flag{Name: "shattering", DefaultText: "22"},
+			expected: "--shattering value\t(default: 22)",
+		},
+		{
+			name:     "int64-slice-flag",
+			fl:       &Int64SliceFlag{Name: "drawers"},
+			expected: "--drawers value\t",
+		},
+		{
+			name:     "int64-slice-flag-with-default-text",
+			fl:       &Int64SliceFlag{Name: "handles", DefaultText: "-2"},
+			expected: "--handles value\t(default: -2)",
+		},
+		{
+			name:     "path-flag",
+			fl:       &PathFlag{Name: "soup"},
+			expected: "--soup value\t",
+		},
+		{
+			name:     "path-flag-with-default-text",
+			fl:       &PathFlag{Name: "stew", DefaultText: "charred/beans"},
+			expected: "--stew value\t(default: charred/beans)",
+		},
+		{
+			name:     "string-flag",
+			fl:       &StringFlag{Name: "arf-sound"},
+			expected: "--arf-sound value\t",
+		},
+		{
+			name:     "string-flag-with-default-text",
+			fl:       &StringFlag{Name: "woof-sound", DefaultText: "urp"},
+			expected: "--woof-sound value\t(default: urp)",
+		},
+		{
+			name:     "string-slice-flag",
+			fl:       &StringSliceFlag{Name: "meow-sounds"},
+			expected: "--meow-sounds value\t",
+		},
+		{
+			name:     "string-slice-flag-with-default-text",
+			fl:       &StringSliceFlag{Name: "moo-sounds", DefaultText: "awoo"},
+			expected: "--moo-sounds value\t(default: awoo)",
+		},
+		{
+			name:     "timestamp-flag",
+			fl:       &TimestampFlag{Name: "eating"},
+			expected: "--eating value\t",
+		},
+		{
+			name:     "timestamp-flag-with-default-text",
+			fl:       &TimestampFlag{Name: "sleeping", DefaultText: "earlier"},
+			expected: "--sleeping value\t(default: earlier)",
+		},
+		{
+			name:     "uint-flag",
+			fl:       &UintFlag{Name: "jars"},
+			expected: "--jars value\t(default: 0)",
+		},
+		{
+			name:     "uint-flag-with-default-text",
+			fl:       &UintFlag{Name: "bottles", DefaultText: "99"},
+			expected: "--bottles value\t(default: 99)",
+		},
+		{
+			name:     "uint64-flag",
+			fl:       &Uint64Flag{Name: "cans"},
+			expected: "--cans value\t(default: 0)",
+		},
+		{
+			name:     "uint64-flag-with-default-text",
+			fl:       &UintFlag{Name: "tubes", DefaultText: "13"},
+			expected: "--tubes value\t(default: 13)",
+		},
+		{
+			name:     "nodoc-flag",
+			fl:       &nodocFlag{Name: "scarecrow"},
+			expected: "",
+		},
+	} {
+		t.Run(tc.name, func(ct *testing.T) {
+			s := stringifyFlag(tc.fl)
+			if s != tc.expected {
+				ct.Errorf("stringified flag %q does not match expected %q", s, tc.expected)
+			}
+		})
+	}
+}
+
 var stringFlagTests = []struct {
 	name     string
 	aliases  []string
@@ -218,7 +411,7 @@ func TestStringFlagWithEnvVarHelpOutput(t *testing.T) {
 	}
 }
 
-var prefixStringFlagTests = []struct {
+var _ = []struct {
 	name     string
 	aliases  []string
 	usage    string
@@ -257,6 +450,14 @@ func TestStringFlagApply_SetsAllNames(t *testing.T) {
 	expect(t, v, "YUUUU")
 }
 
+func TestStringFlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.String("myflag", "foobar", "doc")
+	ctx := NewContext(nil, set, nil)
+	f := &StringFlag{Name: "myflag"}
+	expect(t, f.Get(ctx), "foobar")
+}
+
 var pathFlagTests = []struct {
 	name     string
 	aliases  []string
@@ -308,7 +509,15 @@ func TestPathFlagApply_SetsAllNames(t *testing.T) {
 	expect(t, v, "/path/to/file/PATH")
 }
 
-var envHintFlagTests = []struct {
+func TestPathFlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.String("myflag", "/my/path", "doc")
+	ctx := NewContext(nil, set, nil)
+	f := &PathFlag{Name: "myflag"}
+	expect(t, f.Get(ctx), "/my/path")
+}
+
+var _ = []struct {
 	name     string
 	env      string
 	hinter   FlagEnvHintFunc
@@ -395,7 +604,7 @@ func TestStringSliceFlagApply_SetsAllNames(t *testing.T) {
 	expect(t, err, nil)
 }
 
-func TestStringSliceFlagApply_UsesEnvValues(t *testing.T) {
+func TestStringSliceFlagApply_UsesEnvValues_noDefault(t *testing.T) {
 	defer resetEnv(os.Environ())
 	os.Clearenv()
 	_ = os.Setenv("MY_GOAT", "vincent van goat,scape goat")
@@ -406,7 +615,22 @@ func TestStringSliceFlagApply_UsesEnvValues(t *testing.T) {
 
 	err := set.Parse(nil)
 	expect(t, err, nil)
-	expect(t, val.Value(), NewStringSlice("vincent van goat", "scape goat").Value())
+	expect(t, val.Value(), []string(nil))
+	expect(t, set.Lookup("goat").Value.(*StringSlice).Value(), []string{"vincent van goat", "scape goat"})
+}
+
+func TestStringSliceFlagApply_UsesEnvValues_withDefault(t *testing.T) {
+	defer resetEnv(os.Environ())
+	os.Clearenv()
+	_ = os.Setenv("MY_GOAT", "vincent van goat,scape goat")
+	val := NewStringSlice(`some default`, `values here`)
+	fl := StringSliceFlag{Name: "goat", EnvVars: []string{"MY_GOAT"}, Value: val}
+	set := flag.NewFlagSet("test", 0)
+	_ = fl.Apply(set)
+	err := set.Parse(nil)
+	expect(t, err, nil)
+	expect(t, val.Value(), []string{`some default`, `values here`})
+	expect(t, set.Lookup("goat").Value.(*StringSlice).Value(), []string{"vincent van goat", "scape goat"})
 }
 
 func TestStringSliceFlagApply_DefaultValueWithDestination(t *testing.T) {
@@ -421,6 +645,14 @@ func TestStringSliceFlagApply_DefaultValueWithDestination(t *testing.T) {
 	expect(t, defValue, fl.Destination.Value())
 }
 
+func TestStringSliceFlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.Var(NewStringSlice("a", "b", "c"), "myflag", "doc")
+	ctx := NewContext(nil, set, nil)
+	f := &StringSliceFlag{Name: "myflag"}
+	expect(t, f.Get(ctx), []string{"a", "b", "c"})
+}
+
 var intFlagTests = []struct {
 	name     string
 	expected string
@@ -470,6 +702,14 @@ func TestIntFlagApply_SetsAllNames(t *testing.T) {
 	expect(t, v, 5)
 }
 
+func TestIntFlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.Int("myflag", 42, "doc")
+	ctx := NewContext(nil, set, nil)
+	f := &IntFlag{Name: "myflag"}
+	expect(t, f.Get(ctx), 42)
+}
+
 var int64FlagTests = []struct {
 	name     string
 	expected string
@@ -508,6 +748,14 @@ func TestInt64FlagWithEnvVarHelpOutput(t *testing.T) {
 	}
 }
 
+func TestInt64FlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.Int64("myflag", 42, "doc")
+	ctx := NewContext(nil, set, nil)
+	f := &Int64Flag{Name: "myflag"}
+	expect(t, f.Get(ctx), int64(42))
+}
+
 var uintFlagTests = []struct {
 	name     string
 	expected string
@@ -546,6 +794,14 @@ func TestUintFlagWithEnvVarHelpOutput(t *testing.T) {
 	}
 }
 
+func TestUintFlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.Uint("myflag", 42, "doc")
+	ctx := NewContext(nil, set, nil)
+	f := &UintFlag{Name: "myflag"}
+	expect(t, f.Get(ctx), uint(42))
+}
+
 var uint64FlagTests = []struct {
 	name     string
 	expected string
@@ -584,6 +840,14 @@ func TestUint64FlagWithEnvVarHelpOutput(t *testing.T) {
 	}
 }
 
+func TestUint64FlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.Uint64("myflag", 42, "doc")
+	ctx := NewContext(nil, set, nil)
+	f := &Uint64Flag{Name: "myflag"}
+	expect(t, f.Get(ctx), uint64(42))
+}
+
 var durationFlagTests = []struct {
 	name     string
 	expected string
@@ -633,6 +897,14 @@ func TestDurationFlagApply_SetsAllNames(t *testing.T) {
 	expect(t, v, time.Hour*30)
 }
 
+func TestDurationFlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.Duration("myflag", 42*time.Second, "doc")
+	ctx := NewContext(nil, set, nil)
+	f := &DurationFlag{Name: "myflag"}
+	expect(t, f.Get(ctx), 42*time.Second)
+}
+
 var intSliceFlagTests = []struct {
 	name     string
 	aliases  []string
@@ -722,6 +994,14 @@ func TestIntSliceFlag_SetFromParentContext(t *testing.T) {
 	}
 }
 
+func TestIntSliceFlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.Var(NewIntSlice(1, 2, 3), "myflag", "doc")
+	ctx := NewContext(nil, set, nil)
+	f := &IntSliceFlag{Name: "myflag"}
+	expect(t, f.Get(ctx), []int{1, 2, 3})
+}
+
 var int64SliceFlagTests = []struct {
 	name     string
 	aliases  []string
@@ -818,6 +1098,14 @@ func TestInt64SliceFlag_ReturnNil(t *testing.T) {
 	}
 }
 
+func TestInt64SliceFlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.Var(NewInt64Slice(1, 2, 3), "myflag", "doc")
+	ctx := NewContext(nil, set, nil)
+	f := &Int64SliceFlag{Name: "myflag"}
+	expect(t, f.Get(ctx), []int64{1, 2, 3})
+}
+
 var float64FlagTests = []struct {
 	name     string
 	expected string
@@ -867,6 +1155,14 @@ func TestFloat64FlagApply_SetsAllNames(t *testing.T) {
 	expect(t, v, float64(43.33333))
 }
 
+func TestFloat64FlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.Float64("myflag", 1.23, "doc")
+	ctx := NewContext(nil, set, nil)
+	f := &Float64Flag{Name: "myflag"}
+	expect(t, f.Get(ctx), 1.23)
+}
+
 var float64SliceFlagTests = []struct {
 	name     string
 	aliases  []string
@@ -908,6 +1204,14 @@ func TestFloat64SliceFlagWithEnvVarHelpOutput(t *testing.T) {
 	}
 }
 
+func TestFloat64SliceFlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.Var(NewFloat64Slice(1.23, 4.56), "myflag", "doc")
+	ctx := NewContext(nil, set, nil)
+	f := &Float64SliceFlag{Name: "myflag"}
+	expect(t, f.Get(ctx), []float64{1.23, 4.56})
+}
+
 var genericFlagTests = []struct {
 	name     string
 	value    Generic
@@ -956,6 +1260,14 @@ func TestGenericFlagApply_SetsAllNames(t *testing.T) {
 	expect(t, err, nil)
 }
 
+func TestGenericFlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	set.Var(&Parser{"abc", "def"}, "myflag", "doc")
+	ctx := NewContext(nil, set, nil)
+	f := &GenericFlag{Name: "myflag"}
+	expect(t, f.Get(ctx), &Parser{"abc", "def"})
+}
+
 func TestParseMultiString(t *testing.T) {
 	_ = (&App{
 		Flags: []Flag{
@@ -1109,6 +1421,75 @@ func TestParseMultiStringSliceWithDestinationAndEnv(t *testing.T) {
 	}).Run([]string{"run", "-s", "10", "-s", "20"})
 }
 
+func TestParseMultiFloat64SliceWithDestinationAndEnv(t *testing.T) {
+	defer resetEnv(os.Environ())
+	os.Clearenv()
+	_ = os.Setenv("APP_INTERVALS", "20,30,40")
+
+	dest := &Float64Slice{}
+	_ = (&App{
+		Flags: []Flag{
+			&Float64SliceFlag{Name: "serve", Aliases: []string{"s"}, Destination: dest, EnvVars: []string{"APP_INTERVALS"}},
+		},
+		Action: func(ctx *Context) error {
+			expected := []float64{10, 20}
+			if !reflect.DeepEqual(dest.slice, expected) {
+				t.Errorf("main name not set: %v != %v", expected, ctx.StringSlice("serve"))
+			}
+			if !reflect.DeepEqual(dest.slice, expected) {
+				t.Errorf("short name not set: %v != %v", expected, ctx.StringSlice("s"))
+			}
+			return nil
+		},
+	}).Run([]string{"run", "-s", "10", "-s", "20"})
+}
+
+func TestParseMultiInt64SliceWithDestinationAndEnv(t *testing.T) {
+	defer resetEnv(os.Environ())
+	os.Clearenv()
+	_ = os.Setenv("APP_INTERVALS", "20,30,40")
+
+	dest := &Int64Slice{}
+	_ = (&App{
+		Flags: []Flag{
+			&Int64SliceFlag{Name: "serve", Aliases: []string{"s"}, Destination: dest, EnvVars: []string{"APP_INTERVALS"}},
+		},
+		Action: func(ctx *Context) error {
+			expected := []int64{10, 20}
+			if !reflect.DeepEqual(dest.slice, expected) {
+				t.Errorf("main name not set: %v != %v", expected, ctx.StringSlice("serve"))
+			}
+			if !reflect.DeepEqual(dest.slice, expected) {
+				t.Errorf("short name not set: %v != %v", expected, ctx.StringSlice("s"))
+			}
+			return nil
+		},
+	}).Run([]string{"run", "-s", "10", "-s", "20"})
+}
+
+func TestParseMultiIntSliceWithDestinationAndEnv(t *testing.T) {
+	defer resetEnv(os.Environ())
+	os.Clearenv()
+	_ = os.Setenv("APP_INTERVALS", "20,30,40")
+
+	dest := &IntSlice{}
+	_ = (&App{
+		Flags: []Flag{
+			&IntSliceFlag{Name: "serve", Aliases: []string{"s"}, Destination: dest, EnvVars: []string{"APP_INTERVALS"}},
+		},
+		Action: func(ctx *Context) error {
+			expected := []int{10, 20}
+			if !reflect.DeepEqual(dest.slice, expected) {
+				t.Errorf("main name not set: %v != %v", expected, ctx.StringSlice("serve"))
+			}
+			if !reflect.DeepEqual(dest.slice, expected) {
+				t.Errorf("short name not set: %v != %v", expected, ctx.StringSlice("s"))
+			}
+			return nil
+		},
+	}).Run([]string{"run", "-s", "10", "-s", "20"})
+}
+
 func TestParseMultiStringSliceWithDefaultsUnset(t *testing.T) {
 	_ = (&App{
 		Flags: []Flag{
@@ -1860,7 +2241,7 @@ func TestFlagFromFile(t *testing.T) {
 	}
 
 	for _, filePathTest := range filePathTests {
-		got, _ := flagFromEnvOrFile(filePathTest.name, filePathTest.path)
+		got, _, _ := flagFromEnvOrFile(filePathTest.name, filePathTest.path)
 		if want := filePathTest.expected; got != want {
 			t.Errorf("Did not expect %v - Want %v", got, want)
 		}
@@ -1983,6 +2364,27 @@ func TestTimestampFlagApply_Fail_Parse_Wrong_Time(t *testing.T) {
 	expect(t, err, fmt.Errorf("invalid value \"2006-01-02T15:04:05Z\" for flag -time: parsing time \"2006-01-02T15:04:05Z\" as \"Jan 2, 2006 at 3:04pm (MST)\": cannot parse \"2006-01-02T15:04:05Z\" as \"Jan\""))
 }
 
+func TestTimestampFlagApply_Timezoned(t *testing.T) {
+	pdt := time.FixedZone("PDT", -7*60*60)
+	expectedResult, _ := time.Parse(time.RFC3339, "2006-01-02T15:04:05Z")
+	fl := TimestampFlag{Name: "time", Aliases: []string{"t"}, Layout: time.ANSIC, Timezone: pdt}
+	set := flag.NewFlagSet("test", 0)
+	_ = fl.Apply(set)
+
+	err := set.Parse([]string{"--time", "Mon Jan 2 08:04:05 2006"})
+	expect(t, err, nil)
+	expect(t, *fl.Value.timestamp, expectedResult.In(pdt))
+}
+
+func TestTimestampFlagValueFromContext(t *testing.T) {
+	set := flag.NewFlagSet("test", 0)
+	now := time.Now()
+	set.Var(NewTimestamp(now), "myflag", "doc")
+	ctx := NewContext(nil, set, nil)
+	f := &TimestampFlag{Name: "myflag"}
+	expect(t, f.Get(ctx), &now)
+}
+
 type flagDefaultTestCase struct {
 	name    string
 	flag    Flag
@@ -1992,43 +2394,43 @@ type flagDefaultTestCase struct {
 
 func TestFlagDefaultValue(t *testing.T) {
 	cases := []*flagDefaultTestCase{
-		&flagDefaultTestCase{
+		{
 			name:    "stringSclice",
 			flag:    &StringSliceFlag{Name: "flag", Value: NewStringSlice("default1", "default2")},
 			toParse: []string{"--flag", "parsed"},
 			expect: `--flag value	(default: "default1", "default2")	(accepts multiple inputs)`,
 		},
-		&flagDefaultTestCase{
+		{
 			name:    "float64Sclice",
 			flag:    &Float64SliceFlag{Name: "flag", Value: NewFloat64Slice(1.1, 2.2)},
 			toParse: []string{"--flag", "13.3"},
 			expect: `--flag value	(default: 1.1, 2.2)	(accepts multiple inputs)`,
 		},
-		&flagDefaultTestCase{
+		{
 			name:    "int64Sclice",
 			flag:    &Int64SliceFlag{Name: "flag", Value: NewInt64Slice(1, 2)},
 			toParse: []string{"--flag", "13"},
 			expect: `--flag value	(default: 1, 2)	(accepts multiple inputs)`,
 		},
-		&flagDefaultTestCase{
+		{
 			name:    "intSclice",
 			flag:    &IntSliceFlag{Name: "flag", Value: NewIntSlice(1, 2)},
 			toParse: []string{"--flag", "13"},
 			expect: `--flag value	(default: 1, 2)	(accepts multiple inputs)`,
 		},
-		&flagDefaultTestCase{
+		{
 			name:    "string",
 			flag:    &StringFlag{Name: "flag", Value: "default"},
 			toParse: []string{"--flag", "parsed"},
 			expect: `--flag value	(default: "default")`,
 		},
-		&flagDefaultTestCase{
+		{
 			name:    "bool",
 			flag:    &BoolFlag{Name: "flag", Value: true},
 			toParse: []string{"--flag", "false"},
 			expect: `--flag	(default: true)`,
 		},
-		&flagDefaultTestCase{
+		{
 			name:    "uint64",
 			flag:    &Uint64Flag{Name: "flag", Value: 1},
 			toParse: []string{"--flag", "13"},
@@ -2048,6 +2450,54 @@ func TestFlagDefaultValue(t *testing.T) {
 	}
 }
 
+type flagValueTestCase struct {
+	name    string
+	flag    Flag
+	toParse []string
+	expect  string
+}
+
+func TestFlagValue(t *testing.T) {
+	cases := []*flagValueTestCase{
+		&flagValueTestCase{
+			name:    "stringSclice",
+			flag:    &StringSliceFlag{Name: "flag", Value: NewStringSlice("default1", "default2")},
+			toParse: []string{"--flag", "parsed,parsed2", "--flag", "parsed3,parsed4"},
+			expect:  `[parsed parsed2 parsed3 parsed4]`,
+		},
+		&flagValueTestCase{
+			name:    "float64Sclice",
+			flag:    &Float64SliceFlag{Name: "flag", Value: NewFloat64Slice(1.1, 2.2)},
+			toParse: []string{"--flag", "13.3,14.4", "--flag", "15.5,16.6"},
+			expect:  `[]float64{13.3, 14.4, 15.5, 16.6}`,
+		},
+		&flagValueTestCase{
+			name:    "int64Sclice",
+			flag:    &Int64SliceFlag{Name: "flag", Value: NewInt64Slice(1, 2)},
+			toParse: []string{"--flag", "13,14", "--flag", "15,16"},
+			expect:  `[]int64{13, 14, 15, 16}`,
+		},
+		&flagValueTestCase{
+			name:    "intSclice",
+			flag:    &IntSliceFlag{Name: "flag", Value: NewIntSlice(1, 2)},
+			toParse: []string{"--flag", "13,14", "--flag", "15,16"},
+			expect:  `[]int{13, 14, 15, 16}`,
+		},
+	}
+	for i, v := range cases {
+		set := flag.NewFlagSet("test", 0)
+		set.SetOutput(ioutil.Discard)
+		_ = v.flag.Apply(set)
+		if err := set.Parse(v.toParse); err != nil {
+			t.Error(err)
+		}
+		f := set.Lookup("flag")
+		if got := f.Value.String(); got != v.expect {
+			t.Errorf("TestFlagValue %d-%s\nexpect:%s\ngot:%s", i, v.name, v.expect, got)
+		}
+	}
+}
+
 func TestTimestampFlagApply_WithDestination(t *testing.T) {
 	var destination Timestamp
 	expectedResult, _ := time.Parse(time.RFC3339, "2006-01-02T15:04:05Z")
@@ -2059,3 +2509,42 @@ func TestTimestampFlagApply_WithDestination(t *testing.T) {
 	expect(t, err, nil)
 	expect(t, *fl.Destination.timestamp, expectedResult)
 }
+
+// Test issue #1254
+// StringSlice() with UseShortOptionHandling causes duplicated entries, depending on the ordering of the flags
+func TestSliceShortOptionHandle(t *testing.T) {
+	wasCalled := false
+	err := (&App{
+		Commands: []*Command{
+			{
+				Name:                   "foobar",
+				UseShortOptionHandling: true,
+				Action: func(ctx *Context) error {
+					wasCalled = true
+					if ctx.Bool("i") != true {
+						t.Error("bool i not set")
+					}
+					if ctx.Bool("t") != true {
+						t.Error("bool i not set")
+					}
+					ss := ctx.StringSlice("net")
+					if !reflect.DeepEqual(ss, []string{"foo"}) {
+						t.Errorf("Got different slice(%v) than expected", ss)
+					}
+					return nil
+				},
+				Flags: []Flag{
+					&StringSliceFlag{Name: "net"},
+					&BoolFlag{Name: "i"},
+					&BoolFlag{Name: "t"},
+				},
+			},
+		},
+	}).Run([]string{"run", "foobar", "--net=foo", "-it"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !wasCalled {
+		t.Fatal("Action callback was never called")
+	}
+}

flag_timestamp.go

@@ -11,6 +11,7 @@ type Timestamp struct {
 	timestamp  *time.Time
 	hasBeenSet bool
 	layout     string
+	location   *time.Location
 }
 
 // Timestamp constructor
@@ -31,9 +32,22 @@ func (t *Timestamp) SetLayout(layout string) {
 	t.layout = layout
 }
 
+// Set perceived timezone of the to-be parsed time string
+func (t *Timestamp) SetLocation(loc *time.Location) {
+	t.location = loc
+}
+
 // Parses the string value to timestamp
 func (t *Timestamp) Set(value string) error {
-	timestamp, err := time.Parse(t.layout, value)
+	var timestamp time.Time
+	var err error
+
+	if t.location != nil {
+		timestamp, err = time.ParseInLocation(t.layout, value, t.location)
+	} else {
+		timestamp, err = time.Parse(t.layout, value)
+	}
+
 	if err != nil {
 		return err
 	}
@@ -58,43 +72,6 @@ func (t *Timestamp) Get() interface{} {
 	return *t
 }
 
-// TimestampFlag is a flag with type time
-type TimestampFlag struct {
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	Layout      string
-	Value       *Timestamp
-	DefaultText string
-	HasBeenSet  bool
-	Destination *Timestamp
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *TimestampFlag) IsSet() bool {
-	return f.HasBeenSet
-}
-
-// String returns a readable representation of this value
-// (for usage defaults)
-func (f *TimestampFlag) String() string {
-	return FlagStringer(f)
-}
-
-// Names returns the names of the flag
-func (f *TimestampFlag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *TimestampFlag) IsRequired() bool {
-	return f.Required
-}
-
 // TakesValue returns true of the flag takes a value, otherwise false
 func (f *TimestampFlag) TakesValue() bool {
 	return true
@@ -105,6 +82,11 @@ func (f *TimestampFlag) GetUsage() string {
 	return f.Usage
 }
 
+// GetCategory returns the category for the flag
+func (f *TimestampFlag) GetCategory() string {
+	return f.Category
+}
+
 // GetValue returns the flags value as string representation and an empty
 // string if the flag takes no value at all.
 func (f *TimestampFlag) GetValue() string {
@@ -114,9 +96,17 @@ func (f *TimestampFlag) GetValue() string {
 	return ""
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetDefaultText returns the default text for this flag
-func (f *TimestampFlag) IsVisible() bool {
+func (f *TimestampFlag) GetDefaultText() string {
-	return !f.Hidden
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	return f.GetValue()
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *TimestampFlag) GetEnvVars() []string {
+	return f.EnvVars
 }
 
 // Apply populates the flag given the flag set and environment
@@ -128,14 +118,16 @@ func (f *TimestampFlag) Apply(set *flag.FlagSet) error {
 		f.Value = &Timestamp{}
 	}
 	f.Value.SetLayout(f.Layout)
+	f.Value.SetLocation(f.Timezone)
 
 	if f.Destination != nil {
 		f.Destination.SetLayout(f.Layout)
+		f.Destination.SetLocation(f.Timezone)
 	}
 
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
 		if err := f.Value.Set(val); err != nil {
-			return fmt.Errorf("could not parse %q as timestamp value for flag %s: %s", val, f.Name, err)
+			return fmt.Errorf("could not parse %q as timestamp value from %s for flag %s: %s", val, source, f.Name, err)
 		}
 		f.HasBeenSet = true
 	}
@@ -151,9 +143,14 @@ func (f *TimestampFlag) Apply(set *flag.FlagSet) error {
 	return nil
 }
 
+// Get returns the flag’s value in the given Context.
+func (f *TimestampFlag) Get(ctx *Context) *time.Time {
+	return ctx.Timestamp(f.Name)
+}
+
 // Timestamp gets the timestamp from a flag name
-func (c *Context) Timestamp(name string) *time.Time {
+func (cCtx *Context) Timestamp(name string) *time.Time {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupTimestamp(name, fs)
 	}
 	return nil

flag_uint.go

@@ -6,42 +6,6 @@ import (
 	"strconv"
 )
 
-// UintFlag is a flag with type uint
-type UintFlag struct {
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	Value       uint
-	DefaultText string
-	Destination *uint
-	HasBeenSet  bool
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *UintFlag) IsSet() bool {
-	return f.HasBeenSet
-}
-
-// String returns a readable representation of this value
-// (for usage defaults)
-func (f *UintFlag) String() string {
-	return FlagStringer(f)
-}
-
-// Names returns the names of the flag
-func (f *UintFlag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *UintFlag) IsRequired() bool {
-	return f.Required
-}
-
 // TakesValue returns true of the flag takes a value, otherwise false
 func (f *UintFlag) TakesValue() bool {
 	return true
@@ -52,18 +16,18 @@ func (f *UintFlag) GetUsage() string {
 	return f.Usage
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetCategory returns the category for the flag
-func (f *UintFlag) IsVisible() bool {
+func (f *UintFlag) GetCategory() string {
-	return !f.Hidden
+	return f.Category
 }
 
 // Apply populates the flag given the flag set and environment
 func (f *UintFlag) Apply(set *flag.FlagSet) error {
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
 		if val != "" {
 			valInt, err := strconv.ParseUint(val, 0, 64)
 			if err != nil {
-				return fmt.Errorf("could not parse %q as uint value for flag %s: %s", val, f.Name, err)
+				return fmt.Errorf("could not parse %q as uint value from %s for flag %s: %s", val, source, f.Name, err)
 			}
 
 			f.Value = uint(valInt)
@@ -88,10 +52,28 @@ func (f *UintFlag) GetValue() string {
 	return fmt.Sprintf("%d", f.Value)
 }
 
+// GetDefaultText returns the default text for this flag
+func (f *UintFlag) GetDefaultText() string {
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	return f.GetValue()
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *UintFlag) GetEnvVars() []string {
+	return f.EnvVars
+}
+
+// Get returns the flag’s value in the given Context.
+func (f *UintFlag) Get(ctx *Context) uint {
+	return ctx.Uint(f.Name)
+}
+
 // Uint looks up the value of a local UintFlag, returns
 // 0 if not found
-func (c *Context) Uint(name string) uint {
+func (cCtx *Context) Uint(name string) uint {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupUint(name, fs)
 	}
 	return 0

flag_uint64.go

@@ -6,42 +6,6 @@ import (
 	"strconv"
 )
 
-// Uint64Flag is a flag with type uint64
-type Uint64Flag struct {
-	Name        string
-	Aliases     []string
-	Usage       string
-	EnvVars     []string
-	FilePath    string
-	Required    bool
-	Hidden      bool
-	Value       uint64
-	DefaultText string
-	Destination *uint64
-	HasBeenSet  bool
-}
-
-// IsSet returns whether or not the flag has been set through env or file
-func (f *Uint64Flag) IsSet() bool {
-	return f.HasBeenSet
-}
-
-// String returns a readable representation of this value
-// (for usage defaults)
-func (f *Uint64Flag) String() string {
-	return FlagStringer(f)
-}
-
-// Names returns the names of the flag
-func (f *Uint64Flag) Names() []string {
-	return flagNames(f.Name, f.Aliases)
-}
-
-// IsRequired returns whether or not the flag is required
-func (f *Uint64Flag) IsRequired() bool {
-	return f.Required
-}
-
 // TakesValue returns true of the flag takes a value, otherwise false
 func (f *Uint64Flag) TakesValue() bool {
 	return true
@@ -52,18 +16,18 @@ func (f *Uint64Flag) GetUsage() string {
 	return f.Usage
 }
 
-// IsVisible returns true if the flag is not hidden, otherwise false
+// GetCategory returns the category for the flag
-func (f *Uint64Flag) IsVisible() bool {
+func (f *Uint64Flag) GetCategory() string {
-	return !f.Hidden
+	return f.Category
 }
 
 // Apply populates the flag given the flag set and environment
 func (f *Uint64Flag) Apply(set *flag.FlagSet) error {
-	if val, ok := flagFromEnvOrFile(f.EnvVars, f.FilePath); ok {
+	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
 		if val != "" {
 			valInt, err := strconv.ParseUint(val, 0, 64)
 			if err != nil {
-				return fmt.Errorf("could not parse %q as uint64 value for flag %s: %s", val, f.Name, err)
+				return fmt.Errorf("could not parse %q as uint64 value from %s for flag %s: %s", val, source, f.Name, err)
 			}
 
 			f.Value = valInt
@@ -88,10 +52,28 @@ func (f *Uint64Flag) GetValue() string {
 	return fmt.Sprintf("%d", f.Value)
 }
 
+// GetDefaultText returns the default text for this flag
+func (f *Uint64Flag) GetDefaultText() string {
+	if f.DefaultText != "" {
+		return f.DefaultText
+	}
+	return f.GetValue()
+}
+
+// GetEnvVars returns the env vars for this flag
+func (f *Uint64Flag) GetEnvVars() []string {
+	return f.EnvVars
+}
+
+// Get returns the flag’s value in the given Context.
+func (f *Uint64Flag) Get(ctx *Context) uint64 {
+	return ctx.Uint64(f.Name)
+}
+
 // Uint64 looks up the value of a local Uint64Flag, returns
 // 0 if not found
-func (c *Context) Uint64(name string) uint64 {
+func (cCtx *Context) Uint64(name string) uint64 {
-	if fs := c.lookupFlagSet(name); fs != nil {
+	if fs := cCtx.lookupFlagSet(name); fs != nil {
 		return lookupUint64(name, fs)
 	}
 	return 0

funcs.go

@@ -21,11 +21,11 @@ type CommandNotFoundFunc func(*Context, string)
 // customized usage error messages.  This function is able to replace the
 // original error messages.  If this function is not set, the "Incorrect usage"
 // is displayed and the execution is interrupted.
-type OnUsageErrorFunc func(context *Context, err error, isSubcommand bool) error
+type OnUsageErrorFunc func(cCtx *Context, err error, isSubcommand bool) error
 
 // ExitErrHandlerFunc is executed if provided in order to handle exitError values
 // returned by Actions and Before/After functions.
-type ExitErrHandlerFunc func(context *Context, err error)
+type ExitErrHandlerFunc func(cCtx *Context, err error)
 
 // FlagStringFunc is used by the help generation to display a flag, which is
 // expected to be a single line.

go.mod

@@ -1,9 +1,13 @@
 module github.com/urfave/cli/v2
 
-go 1.11
+go 1.18
 
 require (
-	github.com/BurntSushi/toml v0.3.1
+	github.com/BurntSushi/toml v1.1.0
-	github.com/cpuguy83/go-md2man/v2 v2.0.1
+	github.com/cpuguy83/go-md2man/v2 v2.0.2
-	gopkg.in/yaml.v2 v2.2.8
+	github.com/xrash/smetrics v0.0.0-20201216005158-039620a65673
+	golang.org/x/text v0.3.7
+	gopkg.in/yaml.v3 v3.0.1
 )
+
+require github.com/russross/blackfriday/v2 v2.1.0 // indirect

go.sum

@@ -1,10 +1,18 @@
-github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
+github.com/BurntSushi/toml v1.1.0 h1:ksErzDEI1khOiGPgpwuI7x2ebx/uXQNw7xJpn9Eq1+I=
-github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/BurntSushi/toml v1.1.0/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
 github.com/cpuguy83/go-md2man/v2 v2.0.1 h1:r/myEWzV9lfsM1tFLgDyu0atFtJ1fXn261LKYj/3DxU=
 github.com/cpuguy83/go-md2man/v2 v2.0.1/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
+github.com/cpuguy83/go-md2man/v2 v2.0.2 h1:p1EgwI/C7NhT0JmVkwCD2ZBK8j4aeHQX2pMHHBfMQ6w=
+github.com/cpuguy83/go-md2man/v2 v2.0.2/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
 github.com/russross/blackfriday/v2 v2.1.0 h1:JIOH55/0cWyOuilr9/qlrm0BSXldqnqwMsf35Ld67mk=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/xrash/smetrics v0.0.0-20201216005158-039620a65673 h1:bAn7/zixMGCfxrRTfdpNzjtPYqr8smhKouy9mxVdGPU=
+github.com/xrash/smetrics v0.0.0-20201216005158-039620a65673/go.mod h1:N3UwUGtsrSj3ccvlPHLoLsHnpR27oXr4ZE984MbSER8=
+golang.org/x/text v0.3.7 h1:olpwvP2KacW1ZWvsR7uQhoyTYvKAupfQrRGBFM352Gk=
+golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e h1:FDhOuMEY4JVRztM/gsbk+IKUQ8kj74bxZrgw87eMMVc=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v2 v2.2.8 h1:obN1ZagJSUGI0Ek/LBmuj4SNLPfIny3KsKFopxRdj10=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
-gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

help.go

@@ -10,34 +10,39 @@ import (
 	"unicode/utf8"
 )
 
+const (
+	helpName  = "help"
+	helpAlias = "h"
+)
+
 var helpCommand = &Command{
-	Name:      "help",
+	Name:      helpName,
-	Aliases:   []string{"h"},
+	Aliases:   []string{helpAlias},
 	Usage:     "Shows a list of commands or help for one command",
 	ArgsUsage: "[command]",
-	Action: func(c *Context) error {
+	Action: func(cCtx *Context) error {
-		args := c.Args()
+		args := cCtx.Args()
 		if args.Present() {
-			return ShowCommandHelp(c, args.First())
+			return ShowCommandHelp(cCtx, args.First())
 		}
 
-		_ = ShowAppHelp(c)
+		_ = ShowAppHelp(cCtx)
 		return nil
 	},
 }
 
 var helpSubcommand = &Command{
-	Name:      "help",
+	Name:      helpName,
-	Aliases:   []string{"h"},
+	Aliases:   []string{helpAlias},
 	Usage:     "Shows a list of commands or help for one command",
 	ArgsUsage: "[command]",
-	Action: func(c *Context) error {
+	Action: func(cCtx *Context) error {
-		args := c.Args()
+		args := cCtx.Args()
 		if args.Present() {
-			return ShowCommandHelp(c, args.First())
+			return ShowCommandHelp(cCtx, args.First())
 		}
 
-		return ShowSubcommandHelp(c)
+		return ShowSubcommandHelp(cCtx)
 	},
 }
 
@@ -59,6 +64,11 @@ var HelpPrinter helpPrinter = printHelp
 // HelpPrinterCustom is a function that writes the help output. It is used as
 // the default implementation of HelpPrinter, and may be called directly if
 // the ExtraInfo field is set on an App.
+//
+// In the default implementation, if the customFuncs argument contains a
+// "wrapAt" key, which is a function which takes no arguments and returns
+// an int, this int value will be used to produce a "wrap" function used
+// by the default template to wrap long lines.
 var HelpPrinterCustom helpPrinterCustom = printHelpCustom
 
 // VersionPrinter prints the version for the App
@@ -71,30 +81,30 @@ func ShowAppHelpAndExit(c *Context, exitCode int) {
 }
 
 // ShowAppHelp is an action that displays the help.
-func ShowAppHelp(c *Context) error {
+func ShowAppHelp(cCtx *Context) error {
-	tpl := c.App.CustomAppHelpTemplate
+	tpl := cCtx.App.CustomAppHelpTemplate
 	if tpl == "" {
 		tpl = AppHelpTemplate
 	}
 
-	if c.App.ExtraInfo == nil {
+	if cCtx.App.ExtraInfo == nil {
-		HelpPrinter(c.App.Writer, tpl, c.App)
+		HelpPrinter(cCtx.App.Writer, tpl, cCtx.App)
 		return nil
 	}
 
 	customAppData := func() map[string]interface{} {
 		return map[string]interface{}{
-			"ExtraInfo": c.App.ExtraInfo,
+			"ExtraInfo": cCtx.App.ExtraInfo,
 		}
 	}
-	HelpPrinterCustom(c.App.Writer, tpl, c.App, customAppData())
+	HelpPrinterCustom(cCtx.App.Writer, tpl, cCtx.App, customAppData())
 
 	return nil
 }
 
 // DefaultAppComplete prints the list of subcommands as the default app completion method
-func DefaultAppComplete(c *Context) {
+func DefaultAppComplete(cCtx *Context) {
-	DefaultCompleteWithFlags(nil)(c)
+	DefaultCompleteWithFlags(nil)(cCtx)
 }
 
 func printCommandSuggestions(commands []*Command, writer io.Writer) {
@@ -102,7 +112,7 @@ func printCommandSuggestions(commands []*Command, writer io.Writer) {
 		if command.Hidden {
 			continue
 		}
-		if os.Getenv("_CLI_ZSH_AUTOCOMPLETE_HACK") == "1" {
+		if strings.HasSuffix(os.Getenv("SHELL"), "zsh") {
 			for _, name := range command.Names() {
 				_, _ = fmt.Fprintf(writer, "%s:%s\n", name, command.Usage)
 			}
@@ -159,23 +169,30 @@ func printFlagSuggestions(lastArg string, flags []Flag, writer io.Writer) {
 	}
 }
 
-func DefaultCompleteWithFlags(cmd *Command) func(c *Context) {
+func DefaultCompleteWithFlags(cmd *Command) func(cCtx *Context) {
-	return func(c *Context) {
+	return func(cCtx *Context) {
 		if len(os.Args) > 2 {
 			lastArg := os.Args[len(os.Args)-2]
+
 			if strings.HasPrefix(lastArg, "-") {
-				printFlagSuggestions(lastArg, c.App.Flags, c.App.Writer)
 				if cmd != nil {
-					printFlagSuggestions(lastArg, cmd.Flags, c.App.Writer)
+					printFlagSuggestions(lastArg, cmd.Flags, cCtx.App.Writer)
+
+					return
 				}
+
+				printFlagSuggestions(lastArg, cCtx.App.Flags, cCtx.App.Writer)
+
 				return
 			}
 		}
+
 		if cmd != nil {
-			printCommandSuggestions(cmd.Subcommands, c.App.Writer)
+			printCommandSuggestions(cmd.Subcommands, cCtx.App.Writer)
-		} else {
+			return
-			printCommandSuggestions(c.App.Commands, c.App.Writer)
 		}
+
+		printCommandSuggestions(cCtx.App.Commands, cCtx.App.Writer)
 	}
 }
 
@@ -207,7 +224,13 @@ func ShowCommandHelp(ctx *Context, command string) error {
 	}
 
 	if ctx.App.CommandNotFound == nil {
-		return Exit(fmt.Sprintf("No help topic for '%v'", command), 3)
+		errMsg := fmt.Sprintf("No help topic for '%v'", command)
+		if ctx.App.Suggest {
+			if suggestion := SuggestCommand(ctx.App.Commands, command); suggestion != "" {
+				errMsg += ". " + suggestion
+			}
+		}
+		return Exit(errMsg, 3)
 	}
 
 	ctx.App.CommandNotFound(ctx, command)
@@ -221,32 +244,32 @@ func ShowSubcommandHelpAndExit(c *Context, exitCode int) {
 }
 
 // ShowSubcommandHelp prints help for the given subcommand
-func ShowSubcommandHelp(c *Context) error {
+func ShowSubcommandHelp(cCtx *Context) error {
-	if c == nil {
+	if cCtx == nil {
 		return nil
 	}
 
-	if c.Command != nil {
+	if cCtx.Command != nil {
-		return ShowCommandHelp(c, c.Command.Name)
+		return ShowCommandHelp(cCtx, cCtx.Command.Name)
 	}
 
-	return ShowCommandHelp(c, "")
+	return ShowCommandHelp(cCtx, "")
 }
 
 // ShowVersion prints the version number of the App
-func ShowVersion(c *Context) {
+func ShowVersion(cCtx *Context) {
-	VersionPrinter(c)
+	VersionPrinter(cCtx)
 }
 
-func printVersion(c *Context) {
+func printVersion(cCtx *Context) {
-	_, _ = fmt.Fprintf(c.App.Writer, "%v version %v\n", c.App.Name, c.App.Version)
+	_, _ = fmt.Fprintf(cCtx.App.Writer, "%v version %v\n", cCtx.App.Name, cCtx.App.Version)
 }
 
 // ShowCompletions prints the lists of commands within a given context
-func ShowCompletions(c *Context) {
+func ShowCompletions(cCtx *Context) {
-	a := c.App
+	a := cCtx.App
 	if a != nil && a.BashComplete != nil {
-		a.BashComplete(c)
+		a.BashComplete(cCtx)
 	}
 }
 
@@ -268,12 +291,29 @@ func ShowCommandCompletions(ctx *Context, command string) {
 // The customFuncs map will be combined with a default template.FuncMap to
 // allow using arbitrary functions in template rendering.
 func printHelpCustom(out io.Writer, templ string, data interface{}, customFuncs map[string]interface{}) {
+
+	const maxLineLength = 10000
+
 	funcMap := template.FuncMap{
 		"join":    strings.Join,
 		"indent":  indent,
 		"nindent": nindent,
 		"trim":    strings.TrimSpace,
+		"wrap":    func(input string, offset int) string { return wrap(input, offset, maxLineLength) },
+		"offset":  offset,
 	}
+
+	if customFuncs["wrapAt"] != nil {
+		if wa, ok := customFuncs["wrapAt"]; ok {
+			if waf, ok := wa.(func() int); ok {
+				wrapAt := waf()
+				customFuncs["wrap"] = func(input string, offset int) string {
+					return wrap(input, offset, wrapAt)
+				}
+			}
+		}
+	}
+
 	for key, value := range customFuncs {
 		funcMap[key] = value
 	}
@@ -297,20 +337,20 @@ func printHelp(out io.Writer, templ string, data interface{}) {
 	HelpPrinterCustom(out, templ, data, nil)
 }
 
-func checkVersion(c *Context) bool {
+func checkVersion(cCtx *Context) bool {
 	found := false
 	for _, name := range VersionFlag.Names() {
-		if c.Bool(name) {
+		if cCtx.Bool(name) {
 			found = true
 		}
 	}
 	return found
 }
 
-func checkHelp(c *Context) bool {
+func checkHelp(cCtx *Context) bool {
 	found := false
 	for _, name := range HelpFlag.Names() {
-		if c.Bool(name) {
+		if cCtx.Bool(name) {
 			found = true
 		}
 	}
@@ -326,9 +366,9 @@ func checkCommandHelp(c *Context, name string) bool {
 	return false
 }
 
-func checkSubcommandHelp(c *Context) bool {
+func checkSubcommandHelp(cCtx *Context) bool {
-	if c.Bool("h") || c.Bool("help") {
+	if cCtx.Bool("h") || cCtx.Bool("help") {
-		_ = ShowSubcommandHelp(c)
+		_ = ShowSubcommandHelp(cCtx)
 		return true
 	}
 
@@ -350,20 +390,20 @@ func checkShellCompleteFlag(a *App, arguments []string) (bool, []string) {
 	return true, arguments[:pos]
 }
 
-func checkCompletions(c *Context) bool {
+func checkCompletions(cCtx *Context) bool {
-	if !c.shellComplete {
+	if !cCtx.shellComplete {
 		return false
 	}
 
-	if args := c.Args(); args.Present() {
+	if args := cCtx.Args(); args.Present() {
 		name := args.First()
-		if cmd := c.App.Command(name); cmd != nil {
+		if cmd := cCtx.App.Command(name); cmd != nil {
 			// let the command handle the completion
 			return false
 		}
 	}
 
-	ShowCompletions(c)
+	ShowCompletions(cCtx)
 	return true
 }
 
@@ -384,3 +424,55 @@ func indent(spaces int, v string) string {
 func nindent(spaces int, v string) string {
 	return "\n" + indent(spaces, v)
 }
+
+func wrap(input string, offset int, wrapAt int) string {
+	var sb strings.Builder
+
+	lines := strings.Split(input, "\n")
+
+	padding := strings.Repeat(" ", offset)
+
+	for i, line := range lines {
+		if i != 0 {
+			sb.WriteString(padding)
+		}
+
+		sb.WriteString(wrapLine(line, offset, wrapAt, padding))
+
+		if i != len(lines)-1 {
+			sb.WriteString("\n")
+		}
+	}
+
+	return sb.String()
+}
+
+func wrapLine(input string, offset int, wrapAt int, padding string) string {
+	if wrapAt <= offset || len(input) <= wrapAt-offset {
+		return input
+	}
+
+	lineWidth := wrapAt - offset
+	words := strings.Fields(input)
+	if len(words) == 0 {
+		return input
+	}
+
+	wrapped := words[0]
+	spaceLeft := lineWidth - len(wrapped)
+	for _, word := range words[1:] {
+		if len(word)+1 > spaceLeft {
+			wrapped += "\n" + padding + word
+			spaceLeft = lineWidth - len(word)
+		} else {
+			wrapped += " " + word
+			spaceLeft -= 1 + len(word)
+		}
+	}
+
+	return wrapped
+}
+
+func offset(input string, fixed int) int {
+	return len(input) + fixed
+}

help_test.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"os"
 	"runtime"
 	"strings"
 	"testing"
@@ -1037,3 +1038,311 @@ func TestHideHelpCommand_WithSubcommands(t *testing.T) {
 		t.Errorf("Run returned unexpected error: %v", err)
 	}
 }
+
+func TestDefaultCompleteWithFlags(t *testing.T) {
+	origEnv := os.Environ()
+	origArgv := os.Args
+
+	t.Cleanup(func() {
+		os.Args = origArgv
+		resetEnv(origEnv)
+	})
+
+	os.Setenv("SHELL", "bash")
+
+	for _, tc := range []struct {
+		name     string
+		c        *Context
+		cmd      *Command
+		argv     []string
+		expected string
+	}{
+		{
+			name:     "empty",
+			c:        &Context{App: &App{}},
+			cmd:      &Command{},
+			argv:     []string{"prog", "cmd"},
+			expected: "",
+		},
+		{
+			name: "typical-flag-suggestion",
+			c: &Context{App: &App{
+				Name: "cmd",
+				Flags: []Flag{
+					&BoolFlag{Name: "happiness"},
+					&Int64Flag{Name: "everybody-jump-on"},
+				},
+				Commands: []*Command{
+					{Name: "putz"},
+				},
+			}},
+			cmd: &Command{
+				Flags: []Flag{
+					&BoolFlag{Name: "excitement"},
+					&StringFlag{Name: "hat-shape"},
+				},
+			},
+			argv:     []string{"cmd", "--e", "--generate-bash-completion"},
+			expected: "--excitement\n",
+		},
+		{
+			name: "typical-command-suggestion",
+			c: &Context{App: &App{
+				Name: "cmd",
+				Flags: []Flag{
+					&BoolFlag{Name: "happiness"},
+					&Int64Flag{Name: "everybody-jump-on"},
+				},
+			}},
+			cmd: &Command{
+				Name: "putz",
+				Subcommands: []*Command{
+					{Name: "futz"},
+				},
+				Flags: []Flag{
+					&BoolFlag{Name: "excitement"},
+					&StringFlag{Name: "hat-shape"},
+				},
+			},
+			argv:     []string{"cmd", "--generate-bash-completion"},
+			expected: "futz\n",
+		},
+	} {
+		t.Run(tc.name, func(ct *testing.T) {
+			writer := &bytes.Buffer{}
+			tc.c.App.Writer = writer
+
+			os.Args = tc.argv
+			f := DefaultCompleteWithFlags(tc.cmd)
+			f(tc.c)
+
+			written := writer.String()
+
+			if written != tc.expected {
+				ct.Errorf("written help does not match expected %q != %q", written, tc.expected)
+			}
+		})
+	}
+}
+
+func TestWrappedHelp(t *testing.T) {
+
+	// Reset HelpPrinter after this test.
+	defer func(old helpPrinter) {
+		HelpPrinter = old
+	}(HelpPrinter)
+
+	output := new(bytes.Buffer)
+	app := &App{
+		Writer: output,
+		Flags: []Flag{
+			&BoolFlag{Name: "foo",
+				Aliases: []string{"h"},
+				Usage:   "here's a really long help text line, let's see where it wraps. blah blah blah and so on.",
+			},
+		},
+		Usage:     "here's a sample App.Usage string long enough that it should be wrapped in this test",
+		UsageText: "i'm not sure how App.UsageText differs from App.Usage, but this should also be wrapped in this test",
+		// TODO: figure out how to make ArgsUsage appear in the help text, and test that
+		Description: `here's a sample App.Description string long enough that it should be wrapped in this test
+
+with a newline
+   and an indented line`,
+		Copyright: `Here's a sample copyright text string long enough that it should be wrapped.
+Including newlines.
+   And also indented lines.
+
+
+And then another long line. Blah blah blah does anybody ever read these things?`,
+	}
+
+	c := NewContext(app, nil, nil)
+
+	HelpPrinter = func(w io.Writer, templ string, data interface{}) {
+		funcMap := map[string]interface{}{
+			"wrapAt": func() int {
+				return 30
+			},
+		}
+
+		HelpPrinterCustom(w, templ, data, funcMap)
+	}
+
+	_ = ShowAppHelp(c)
+
+	expected := `NAME:
+    - here's a sample
+      App.Usage string long
+      enough that it should be
+      wrapped in this test
+
+USAGE:
+   i'm not sure how
+   App.UsageText differs from
+   App.Usage, but this should
+   also be wrapped in this
+   test
+
+DESCRIPTION:
+   here's a sample
+   App.Description string long
+   enough that it should be
+   wrapped in this test
+   
+   with a newline
+      and an indented line
+
+GLOBAL OPTIONS:
+   --foo, -h here's a
+      really long help text
+      line, let's see where it
+      wraps. blah blah blah
+      and so on. (default:
+      false)
+
+COPYRIGHT:
+   Here's a sample copyright
+   text string long enough
+   that it should be wrapped.
+   Including newlines.
+      And also indented lines.
+   
+   
+   And then another long line.
+   Blah blah blah does anybody
+   ever read these things?
+`
+
+	if output.String() != expected {
+		t.Errorf("Unexpected wrapping, got:\n%s\nexpected: %s",
+			output.String(), expected)
+	}
+}
+
+func TestWrappedCommandHelp(t *testing.T) {
+
+	// Reset HelpPrinter after this test.
+	defer func(old helpPrinter) {
+		HelpPrinter = old
+	}(HelpPrinter)
+
+	output := new(bytes.Buffer)
+	app := &App{
+		Writer: output,
+		Commands: []*Command{
+			{
+				Name:        "add",
+				Aliases:     []string{"a"},
+				Usage:       "add a task to the list",
+				UsageText:   "this is an even longer way of describing adding a task to the list",
+				Description: "and a description long enough to wrap in this test case",
+				Action: func(c *Context) error {
+					return nil
+				},
+			},
+		},
+	}
+
+	c := NewContext(app, nil, nil)
+
+	HelpPrinter = func(w io.Writer, templ string, data interface{}) {
+		funcMap := map[string]interface{}{
+			"wrapAt": func() int {
+				return 30
+			},
+		}
+
+		HelpPrinterCustom(w, templ, data, funcMap)
+	}
+
+	_ = ShowCommandHelp(c, "add")
+
+	expected := `NAME:
+    - add a task to the list
+
+USAGE:
+   this is an even longer way
+   of describing adding a task
+   to the list
+
+DESCRIPTION:
+   and a description long
+   enough to wrap in this test
+   case
+`
+
+	if output.String() != expected {
+		t.Errorf("Unexpected wrapping, got:\n%s\nexpected: %s",
+			output.String(), expected)
+	}
+}
+
+func TestWrappedSubcommandHelp(t *testing.T) {
+
+	// Reset HelpPrinter after this test.
+	defer func(old helpPrinter) {
+		HelpPrinter = old
+	}(HelpPrinter)
+
+	output := new(bytes.Buffer)
+	app := &App{
+		Name:   "cli.test",
+		Writer: output,
+		Commands: []*Command{
+			{
+				Name:        "bar",
+				Aliases:     []string{"a"},
+				Usage:       "add a task to the list",
+				UsageText:   "this is an even longer way of describing adding a task to the list",
+				Description: "and a description long enough to wrap in this test case",
+				Action: func(c *Context) error {
+					return nil
+				},
+				Subcommands: []*Command{
+					{
+						Name:      "grok",
+						Usage:     "remove an existing template",
+						UsageText: "longer usage text goes here, la la la, hopefully this is long enough to wrap even more",
+						Action: func(c *Context) error {
+							return nil
+						},
+					},
+				},
+			},
+		},
+	}
+
+	HelpPrinter = func(w io.Writer, templ string, data interface{}) {
+		funcMap := map[string]interface{}{
+			"wrapAt": func() int {
+				return 30
+			},
+		}
+
+		HelpPrinterCustom(w, templ, data, funcMap)
+	}
+
+	_ = app.Run([]string{"foo", "bar", "grok", "--help"})
+
+	expected := `NAME:
+   cli.test bar grok - remove
+                       an
+                       existing
+                       template
+
+USAGE:
+   longer usage text goes
+   here, la la la, hopefully
+   this is long enough to wrap
+   even more
+
+OPTIONS:
+   --help, -h  show help (default: false)
+   
+`
+
+	if output.String() != expected {
+		t.Errorf("Unexpected wrapping, got:\n%s\nexpected: %s",
+			output.String(), expected)
+	}
+}

internal/build/build.go

@@ -6,19 +6,45 @@ import (
 	"bufio"
 	"bytes"
 	"fmt"
-	"io/ioutil"
 	"log"
 	"math"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"strings"
 
 	"github.com/urfave/cli/v2"
 )
 
-var packages = []string{"cli", "altsrc"}
+const (
+	badNewsEmoji      = "🚨"
+	goodNewsEmoji     = "✨"
+	checksPassedEmoji = "✅"
+
+	v2diffWarning = `
+# The unified diff above indicates that the public API surface area
+# has changed. If you feel that the changes are acceptable and adhere
+# to the semantic versioning promise of the v2.x series described in
+# docs/CONTRIBUTING.md, please run the following command to promote
+# the current go docs:
+#
+#     make v2approve
+#
+`
+)
 
 func main() {
+	top, err := func() (string, error) {
+		if v, err := sh("git", "rev-parse", "--show-toplevel"); err == nil {
+			return strings.TrimSpace(v), nil
+		}
+
+		return os.Getwd()
+	}()
+	if err != nil {
+		log.Fatal(err)
+	}
+
 	app := cli.NewApp()
 
 	app.Name = "builder"
@@ -37,22 +63,56 @@ func main() {
 			Name:   "gfmrun",
 			Action: GfmrunActionFunc,
 		},
-		{
-			Name:   "toc",
-			Action: TocActionFunc,
-		},
 		{
 			Name:   "check-binary-size",
 			Action: checkBinarySizeActionFunc,
 		},
+		{
+			Name:   "generate",
+			Action: GenerateActionFunc,
+		},
+		{
+			Name: "v2diff",
+			Flags: []cli.Flag{
+				&cli.BoolFlag{Name: "color", Value: false},
+			},
+			Action: V2Diff,
+		},
+		{
+			Name:   "v2approve",
+			Action: V2Approve,
+		},
+	}
+	app.Flags = []cli.Flag{
+		&cli.StringFlag{
+			Name:  "tags",
+			Usage: "set build tags",
+		},
+		&cli.PathFlag{
+			Name:  "top",
+			Value: top,
+		},
+		&cli.StringSliceFlag{
+			Name:  "packages",
+			Value: cli.NewStringSlice("cli", "altsrc", "internal/build", "internal/genflags"),
+		},
 	}
 
-	err := app.Run(os.Args)
+	if err := app.Run(os.Args); err != nil {
-	if err != nil {
 		log.Fatal(err)
 	}
 }
 
+func sh(exe string, args ...string) (string, error) {
+	cmd := exec.Command(exe, args...)
+	cmd.Stdin = os.Stdin
+	cmd.Stderr = os.Stderr
+
+	fmt.Fprintf(os.Stderr, "# ---> %s\n", cmd)
+	outBytes, err := cmd.Output()
+	return string(outBytes), err
+}
+
 func runCmd(arg string, args ...string) error {
 	cmd := exec.Command(arg, args...)
 
@@ -60,80 +120,102 @@ func runCmd(arg string, args ...string) error {
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
 
+	fmt.Fprintf(os.Stderr, "# ---> %s\n", cmd)
 	return cmd.Run()
 }
 
-func VetActionFunc(_ *cli.Context) error {
+func VetActionFunc(cCtx *cli.Context) error {
-	return runCmd("go", "vet")
+	return runCmd("go", "vet", cCtx.Path("top")+"/...")
 }
 
 func TestActionFunc(c *cli.Context) error {
-	for _, pkg := range packages {
+	tags := c.String("tags")
-		var packageName string
 
-		if pkg == "cli" {
+	for _, pkg := range c.StringSlice("packages") {
-			packageName = "github.com/urfave/cli/v2"
+		packageName := "github.com/urfave/cli/v2"
-		} else {
+
+		if pkg != "cli" {
 			packageName = fmt.Sprintf("github.com/urfave/cli/v2/%s", pkg)
 		}
 
-		coverProfile := fmt.Sprintf("--coverprofile=%s.coverprofile", pkg)
+		if err := runCmd(
-
+			"go", "test",
-		err := runCmd("go", "test", "-v", coverProfile, packageName)
+			"-tags", tags,
-		if err != nil {
+			"-v",
+			"--coverprofile", pkg+".coverprofile",
+			"--covermode", "count",
+			"--cover", packageName,
+			packageName,
+		); err != nil {
 			return err
 		}
 	}
 
-	return testCleanup()
+	return testCleanup(c.StringSlice("packages"))
 }
 
-func testCleanup() error {
+func testCleanup(packages []string) error {
-	var out bytes.Buffer
+	out := &bytes.Buffer{}
+
+	fmt.Fprintf(out, "mode: count\n")
 
 	for _, pkg := range packages {
-		file, err := os.Open(fmt.Sprintf("%s.coverprofile", pkg))
+		filename := pkg + ".coverprofile"
+
+		lineBytes, err := os.ReadFile(filename)
 		if err != nil {
 			return err
 		}
 
-		b, err := ioutil.ReadAll(file)
+		lines := strings.Split(string(lineBytes), "\n")
-		if err != nil {
-			return err
-		}
 
-		out.Write(b)
+		fmt.Fprintf(out, strings.Join(lines[1:], "\n"))
-		err = file.Close()
-		if err != nil {
-			return err
-		}
 
-		err = os.Remove(fmt.Sprintf("%s.coverprofile", pkg))
+		if err := os.Remove(filename); err != nil {
-		if err != nil {
 			return err
 		}
 	}
 
-	outFile, err := os.Create("coverage.txt")
+	return os.WriteFile("coverage.txt", out.Bytes(), 0644)
-	if err != nil {
-		return err
-	}
-
-	_, err = out.WriteTo(outFile)
-	if err != nil {
-		return err
-	}
-
-	err = outFile.Close()
-	if err != nil {
-		return err
-	}
-
-	return nil
 }
 
-func GfmrunActionFunc(c *cli.Context) error {
+func GfmrunActionFunc(cCtx *cli.Context) error {
-	filename := c.Args().Get(0)
+	top := cCtx.Path("top")
+
+	bash, err := exec.LookPath("bash")
+	if err != nil {
+		return err
+	}
+
+	os.Setenv("SHELL", bash)
+
+	tmpDir, err := os.MkdirTemp("", "urfave-cli*")
+	if err != nil {
+		return err
+	}
+
+	wd, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+
+	if err := os.Chdir(tmpDir); err != nil {
+		return err
+	}
+
+	fmt.Fprintf(cCtx.App.ErrWriter, "# ---> workspace/TMPDIR is %q\n", tmpDir)
+
+	if err := runCmd("go", "work", "init", top); err != nil {
+		return err
+	}
+
+	os.Setenv("TMPDIR", tmpDir)
+
+	if err := os.Chdir(wd); err != nil {
+		return err
+	}
+
+	filename := cCtx.Args().Get(0)
 	if filename == "" {
 		filename = "README.md"
 	}
@@ -162,26 +244,11 @@ func GfmrunActionFunc(c *cli.Context) error {
 		return err
 	}
 
-	return runCmd("gfmrun", "-c", fmt.Sprint(counter), "-s", filename)
+	if err := runCmd("gfmrun", "-c", fmt.Sprint(counter), "-s", filename); err != nil {
-}
-
-func TocActionFunc(c *cli.Context) error {
-	filename := c.Args().Get(0)
-	if filename == "" {
-		filename = "README.md"
-	}
-
-	err := runCmd("markdown-toc", "-i", filename)
-	if err != nil {
 		return err
 	}
 
-	err = runCmd("git", "diff", "--exit-code")
+	return os.RemoveAll(tmpDir)
-	if err != nil {
-		return err
-	}
-
-	return nil
 }
 
 // checkBinarySizeActionFunc checks the size of an example binary to ensure that we are keeping size down
@@ -193,22 +260,26 @@ func checkBinarySizeActionFunc(c *cli.Context) (err error) {
 		cliBuiltFilePath     = "./internal/example-cli/built-example"
 		helloSourceFilePath  = "./internal/example-hello-world/example-hello-world.go"
 		helloBuiltFilePath   = "./internal/example-hello-world/built-example"
-		desiredMinBinarySize = 1.9
 		desiredMaxBinarySize = 2.2
-		badNewsEmoji         = "🚨"
-		goodNewsEmoji        = "✨"
-		checksPassedEmoji    = "✅"
 		mbStringFormatter    = "%.1fMB"
 	)
 
+	desiredMinBinarySize := 1.675
+
+	tags := c.String("tags")
+
+	if strings.Contains(tags, "urfave_cli_no_docs") {
+		desiredMinBinarySize = 1.39
+	}
+
 	// get cli example size
-	cliSize, err := getSize(cliSourceFilePath, cliBuiltFilePath)
+	cliSize, err := getSize(cliSourceFilePath, cliBuiltFilePath, tags)
 	if err != nil {
 		return err
 	}
 
 	// get hello world size
-	helloSize, err := getSize(helloSourceFilePath, helloBuiltFilePath)
+	helloSize, err := getSize(helloSourceFilePath, helloBuiltFilePath, tags)
 	if err != nil {
 		return err
 	}
@@ -270,9 +341,72 @@ func checkBinarySizeActionFunc(c *cli.Context) (err error) {
 	return nil
 }
 
-func getSize(sourcePath string, builtPath string) (size int64, err error) {
+func GenerateActionFunc(cCtx *cli.Context) error {
+	top := cCtx.Path("top")
+
+	cliDocs, err := sh("go", "doc", "-all", top)
+	if err != nil {
+		return err
+	}
+
+	altsrcDocs, err := sh("go", "doc", "-all", filepath.Join(top, "altsrc"))
+	if err != nil {
+		return err
+	}
+
+	if err := os.WriteFile(
+		filepath.Join(top, "godoc-current.txt"),
+		[]byte(cliDocs+altsrcDocs),
+		0644,
+	); err != nil {
+		return err
+	}
+
+	return runCmd("go", "generate", cCtx.Path("top")+"/...")
+}
+
+func V2Diff(cCtx *cli.Context) error {
+	os.Chdir(cCtx.Path("top"))
+
+	err := runCmd(
+		"diff",
+		"--ignore-all-space",
+		"--minimal",
+		"--color="+func() string {
+			if cCtx.Bool("color") {
+				return "always"
+			}
+			return "auto"
+		}(),
+		"--unified",
+		"--label=a/godoc",
+		filepath.Join("testdata", "godoc-v2.x.txt"),
+		"--label=b/godoc",
+		"godoc-current.txt",
+	)
+
+	if err != nil {
+		fmt.Printf("# %v ---> Hey! <---\n", badNewsEmoji)
+		fmt.Println(strings.TrimSpace(v2diffWarning))
+	}
+
+	return err
+}
+
+func V2Approve(cCtx *cli.Context) error {
+	top := cCtx.Path("top")
+
+	return runCmd(
+		"cp",
+		"-v",
+		filepath.Join(top, "godoc-current.txt"),
+		filepath.Join(top, "testdata", "godoc-v2.x.txt"),
+	)
+}
+
+func getSize(sourcePath string, builtPath string, tags string) (size int64, err error) {
 	// build example binary
-	err = runCmd("go", "build", "-o", builtPath, "-ldflags", "-s -w", sourcePath)
+	err = runCmd("go", "build", "-tags", tags, "-o", builtPath, "-ldflags", "-s -w", sourcePath)
 	if err != nil {
 		fmt.Println("issue getting size for example binary")
 		return 0, err

internal/example-cli/example-cli.go

@@ -7,5 +7,5 @@ import (
 )
 
 func main() {
-	(&cli.App{}).Run([]string{})
+	(&cli.App{}).Run([]string{""})
 }

internal/genflags/cmd/genflags/main.go

@@ -0,0 +1,163 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	_ "embed"
+	"log"
+	"os"
+	"os/exec"
+	"os/signal"
+	"path/filepath"
+	"strings"
+	"syscall"
+	"text/template"
+
+	"github.com/urfave/cli/v2"
+	"github.com/urfave/cli/v2/internal/genflags"
+	"gopkg.in/yaml.v3"
+)
+
+const (
+	defaultPackageName = "cli"
+)
+
+func sh(ctx context.Context, exe string, args ...string) (string, error) {
+	cmd := exec.CommandContext(ctx, exe, args...)
+	cmd.Stderr = os.Stderr
+	outBytes, err := cmd.Output()
+	return string(outBytes), err
+}
+
+func main() {
+	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
+	defer stop()
+
+	top := "../../"
+	if v, err := sh(ctx, "git", "rev-parse", "--show-toplevel"); err == nil {
+		top = strings.TrimSpace(v)
+	}
+
+	app := &cli.App{
+		Name:  "genflags",
+		Usage: "Generate flag types for urfave/cli",
+		Flags: []cli.Flag{
+			&cli.PathFlag{
+				Name:    "flag-spec-yaml",
+				Aliases: []string{"f"},
+				Value:   filepath.Join(top, "flag-spec.yaml"),
+			},
+			&cli.PathFlag{
+				Name:    "generated-output",
+				Aliases: []string{"o"},
+				Value:   filepath.Join(top, "zz_generated.flags.go"),
+			},
+			&cli.PathFlag{
+				Name:    "generated-test-output",
+				Aliases: []string{"t"},
+				Value:   filepath.Join(top, "zz_generated.flags_test.go"),
+			},
+			&cli.StringFlag{
+				Name:    "generated-package-name",
+				Aliases: []string{"p"},
+				Value:   defaultPackageName,
+			},
+			&cli.StringFlag{
+				Name:    "generated-test-package-name",
+				Aliases: []string{"T"},
+				Value:   defaultPackageName + "_test",
+			},
+			&cli.StringFlag{
+				Name:    "urfave-cli-namespace",
+				Aliases: []string{"n"},
+				Value:   "",
+			},
+			&cli.StringFlag{
+				Name:    "urfave-cli-test-namespace",
+				Aliases: []string{"N"},
+				Value:   "cli.",
+			},
+		},
+		Action: runGenFlags,
+	}
+
+	if err := app.RunContext(ctx, os.Args); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func runGenFlags(cCtx *cli.Context) error {
+	specBytes, err := os.ReadFile(cCtx.Path("flag-spec-yaml"))
+	if err != nil {
+		return err
+	}
+
+	spec := &genflags.Spec{}
+	if err := yaml.Unmarshal(specBytes, spec); err != nil {
+		return err
+	}
+
+	if cCtx.IsSet("generated-package-name") {
+		spec.PackageName = strings.TrimSpace(cCtx.String("generated-package-name"))
+	}
+
+	if strings.TrimSpace(spec.PackageName) == "" {
+		spec.PackageName = defaultPackageName
+	}
+
+	if cCtx.IsSet("generated-test-package-name") {
+		spec.TestPackageName = strings.TrimSpace(cCtx.String("generated-test-package-name"))
+	}
+
+	if strings.TrimSpace(spec.TestPackageName) == "" {
+		spec.TestPackageName = defaultPackageName + "_test"
+	}
+
+	if cCtx.IsSet("urfave-cli-namespace") {
+		spec.UrfaveCLINamespace = strings.TrimSpace(cCtx.String("urfave-cli-namespace"))
+	}
+
+	if cCtx.IsSet("urfave-cli-test-namespace") {
+		spec.UrfaveCLITestNamespace = strings.TrimSpace(cCtx.String("urfave-cli-test-namespace"))
+	} else {
+		spec.UrfaveCLITestNamespace = "cli."
+	}
+
+	genTmpl, err := template.New("gen").Parse(genflags.TemplateString)
+	if err != nil {
+		return err
+	}
+
+	genTestTmpl, err := template.New("gen_test").Parse(genflags.TestTemplateString)
+	if err != nil {
+		return err
+	}
+
+	genBuf := &bytes.Buffer{}
+	if err := genTmpl.Execute(genBuf, spec); err != nil {
+		return err
+	}
+
+	genTestBuf := &bytes.Buffer{}
+	if err := genTestTmpl.Execute(genTestBuf, spec); err != nil {
+		return err
+	}
+
+	if err := os.WriteFile(cCtx.Path("generated-output"), genBuf.Bytes(), 0644); err != nil {
+		return err
+	}
+
+	if err := os.WriteFile(cCtx.Path("generated-test-output"), genTestBuf.Bytes(), 0644); err != nil {
+		return err
+	}
+
+	if _, err := sh(cCtx.Context, "goimports", "-w", cCtx.Path("generated-output")); err != nil {
+		return err
+	}
+
+	if _, err := sh(cCtx.Context, "goimports", "-w", cCtx.Path("generated-test-output")); err != nil {
+		return err
+	}
+
+	return nil
+}

internal/genflags/generated.gotmpl

@@ -0,0 +1,68 @@
+// WARNING: this file is generated. DO NOT EDIT
+
+package {{.PackageName}}
+
+{{range .SortedFlagTypes}}
+// {{.TypeName}} is a flag with type {{if .ValuePointer}}*{{end}}{{.GoType}}
+type {{.TypeName}} struct {
+  Name string
+
+  Category string
+  DefaultText string
+  FilePath string
+  Usage string
+
+  Required bool
+  Hidden bool
+  HasBeenSet bool
+
+  Value {{if .ValuePointer}}*{{end}}{{.GoType}}
+  Destination *{{.GoType}}
+
+  Aliases []string
+  EnvVars []string
+
+  {{range .StructFields}}
+  {{.Name}} {{.Type}}
+  {{end}}
+}
+
+{{if .GenerateFmtStringerInterface}}
+// String returns a readable representation of this value (for usage defaults)
+func (f *{{.TypeName}}) String() string {
+  return {{$.UrfaveCLINamespace}}FlagStringer(f)
+}
+{{end}}{{/* /if .GenerateFmtStringerInterface */}}
+
+{{if .GenerateFlagInterface}}
+// IsSet returns whether or not the flag has been set through env or file
+func (f *{{.TypeName}}) IsSet() bool {
+  return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *{{.TypeName}}) Names() []string {
+  return {{$.UrfaveCLINamespace}}FlagNames(f.Name, f.Aliases)
+}
+
+{{end}}{{/* /if .GenerateFlagInterface */}}
+
+{{if .GenerateRequiredFlagInterface}}
+// IsRequired returns whether or not the flag is required
+func (f *{{.TypeName}}) IsRequired() bool {
+  return f.Required
+}
+{{end}}{{/* /if .GenerateRequiredFlagInterface */}}
+
+{{if .GenerateVisibleFlagInterface}}
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *{{.TypeName}}) IsVisible() bool {
+	return !f.Hidden
+}
+{{end}}{{/* /if .GenerateVisibleFlagInterface */}}
+{{end}}{{/* /range .SortedFlagTypes */}}
+
+// vim{{/* 👻 */}}:ro
+{{/*
+vim:filetype=gotexttmpl
+*/}}

internal/genflags/generated_test.gotmpl

@@ -0,0 +1,43 @@
+// WARNING: this file is generated. DO NOT EDIT
+
+package {{.TestPackageName}}
+
+{{range .SortedFlagTypes}}
+{{if .GenerateFlagInterface}}
+func Test{{.TypeName}}_SatisfiesFlagInterface(t *testing.T) {
+  var f {{$.UrfaveCLITestNamespace}}Flag = &{{$.UrfaveCLITestNamespace}}{{.TypeName}}{}
+
+  _ = f.IsSet()
+  _ = f.Names()
+}
+{{end}}
+
+{{if .GenerateFmtStringerInterface}}
+func Test{{.TypeName}}_SatisfiesFmtStringerInterface(t *testing.T) {
+  var f fmt.Stringer = &{{$.UrfaveCLITestNamespace}}{{.TypeName}}{}
+
+  _ = f.String()
+}
+{{end}}
+
+{{if .GenerateRequiredFlagInterface}}
+func Test{{.TypeName}}_SatisfiesRequiredFlagInterface(t *testing.T) {
+  var f {{$.UrfaveCLITestNamespace}}RequiredFlag = &{{$.UrfaveCLITestNamespace}}{{.TypeName}}{}
+
+  _ = f.IsRequired()
+}
+{{end}}
+
+{{if .GenerateVisibleFlagInterface}}
+func Test{{.TypeName}}_SatisfiesVisibleFlagInterface(t *testing.T) {
+  var f {{$.UrfaveCLITestNamespace}}VisibleFlag = &{{$.UrfaveCLITestNamespace}}{{.TypeName}}{}
+
+  _ = f.IsVisible()
+}
+{{end}}
+{{end}}
+
+// vim{{/* 👻 */}}:ro
+{{/*
+vim:filetype=gotexttmpl
+*/}}

internal/genflags/package.go

@@ -0,0 +1,34 @@
+package genflags
+
+import (
+	_ "embed"
+	"strings"
+
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
+)
+
+var (
+	//go:embed generated.gotmpl
+	TemplateString string
+
+	//go:embed generated_test.gotmpl
+	TestTemplateString string
+
+	titler = cases.Title(language.Und, cases.NoLower)
+)
+
+func TypeName(goType string, fc *FlagTypeConfig) string {
+	if fc != nil && strings.TrimSpace(fc.TypeName) != "" {
+		return strings.TrimSpace(fc.TypeName)
+	}
+
+	dotSplit := strings.Split(goType, ".")
+	goType = dotSplit[len(dotSplit)-1]
+
+	if strings.HasPrefix(goType, "[]") {
+		return titler.String(strings.TrimPrefix(goType, "[]")) + "SliceFlag"
+	}
+
+	return titler.String(goType) + "Flag"
+}

internal/genflags/package_test.go

@@ -0,0 +1,41 @@
+package genflags_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/urfave/cli/v2/internal/genflags"
+)
+
+func TestTypeName(t *testing.T) {
+	for _, tc := range []struct {
+		gt       string
+		fc       *genflags.FlagTypeConfig
+		expected string
+	}{
+		{gt: "int", fc: nil, expected: "IntFlag"},
+		{gt: "int", fc: &genflags.FlagTypeConfig{}, expected: "IntFlag"},
+		{gt: "int", fc: &genflags.FlagTypeConfig{TypeName: "VeryIntyFlag"}, expected: "VeryIntyFlag"},
+		{gt: "[]bool", fc: nil, expected: "BoolSliceFlag"},
+		{gt: "[]bool", fc: &genflags.FlagTypeConfig{}, expected: "BoolSliceFlag"},
+		{gt: "[]bool", fc: &genflags.FlagTypeConfig{TypeName: "ManyTruthsFlag"}, expected: "ManyTruthsFlag"},
+		{gt: "time.Rumination", fc: nil, expected: "RuminationFlag"},
+		{gt: "time.Rumination", fc: &genflags.FlagTypeConfig{}, expected: "RuminationFlag"},
+		{gt: "time.Rumination", fc: &genflags.FlagTypeConfig{TypeName: "PonderFlag"}, expected: "PonderFlag"},
+	} {
+		t.Run(
+			fmt.Sprintf("type=%s,cfg=%v", tc.gt, func() string {
+				if tc.fc != nil {
+					return tc.fc.TypeName
+				}
+				return "nil"
+			}()),
+			func(ct *testing.T) {
+				actual := genflags.TypeName(tc.gt, tc.fc)
+				if tc.expected != actual {
+					ct.Errorf("expected %q, got %q", tc.expected, actual)
+				}
+			},
+		)
+	}
+}

internal/genflags/spec.go

@@ -0,0 +1,108 @@
+package genflags
+
+import (
+	"sort"
+	"strings"
+)
+
+type Spec struct {
+	FlagTypes              map[string]*FlagTypeConfig `yaml:"flag_types"`
+	PackageName            string                     `yaml:"package_name"`
+	TestPackageName        string                     `yaml:"test_package_name"`
+	UrfaveCLINamespace     string                     `yaml:"urfave_cli_namespace"`
+	UrfaveCLITestNamespace string                     `yaml:"urfave_cli_test_namespace"`
+}
+
+func (gfs *Spec) SortedFlagTypes() []*FlagType {
+	typeNames := []string{}
+
+	for name := range gfs.FlagTypes {
+		if strings.HasPrefix(name, "[]") {
+			name = strings.TrimPrefix(name, "[]") + "Slice"
+		}
+
+		typeNames = append(typeNames, name)
+	}
+
+	sort.Strings(typeNames)
+
+	ret := make([]*FlagType, len(typeNames))
+
+	for i, typeName := range typeNames {
+		ret[i] = &FlagType{
+			GoType: typeName,
+			Config: gfs.FlagTypes[typeName],
+		}
+	}
+
+	return ret
+}
+
+type FlagTypeConfig struct {
+	SkipInterfaces []string           `yaml:"skip_interfaces"`
+	StructFields   []*FlagStructField `yaml:"struct_fields"`
+	TypeName       string             `yaml:"type_name"`
+	ValuePointer   bool               `yaml:"value_pointer"`
+}
+
+type FlagStructField struct {
+	Name string
+	Type string
+}
+
+type FlagType struct {
+	GoType string
+	Config *FlagTypeConfig
+}
+
+func (ft *FlagType) StructFields() []*FlagStructField {
+	if ft.Config == nil || ft.Config.StructFields == nil {
+		return []*FlagStructField{}
+	}
+
+	return ft.Config.StructFields
+}
+
+func (ft *FlagType) ValuePointer() bool {
+	if ft.Config == nil {
+		return false
+	}
+
+	return ft.Config.ValuePointer
+}
+
+func (ft *FlagType) TypeName() string {
+	return TypeName(ft.GoType, ft.Config)
+}
+
+func (ft *FlagType) GenerateFmtStringerInterface() bool {
+	return ft.skipInterfaceNamed("fmt.Stringer")
+}
+
+func (ft *FlagType) GenerateFlagInterface() bool {
+	return ft.skipInterfaceNamed("Flag")
+}
+
+func (ft *FlagType) GenerateRequiredFlagInterface() bool {
+	return ft.skipInterfaceNamed("RequiredFlag")
+}
+
+func (ft *FlagType) GenerateVisibleFlagInterface() bool {
+	return ft.skipInterfaceNamed("VisibleFlag")
+}
+
+func (ft *FlagType) skipInterfaceNamed(name string) bool {
+	if ft.Config == nil {
+		return true
+	}
+
+	lowName := strings.ToLower(name)
+
+	for _, interfaceName := range ft.Config.SkipInterfaces {
+		if strings.ToLower(interfaceName) == lowName {
+			return false
+		}
+	}
+
+	return true
+}

internal/genflags/spec_test.go

@@ -0,0 +1,112 @@
+package genflags_test
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/urfave/cli/v2/internal/genflags"
+)
+
+func TestSpec_SortedFlagTypes(t *testing.T) {
+	spec := &genflags.Spec{
+		FlagTypes: map[string]*genflags.FlagTypeConfig{
+			"nerf": &genflags.FlagTypeConfig{},
+			"gerf": nil,
+		},
+	}
+
+	actual := spec.SortedFlagTypes()
+	expected := []*genflags.FlagType{
+		{
+			GoType: "gerf",
+			Config: nil,
+		},
+		{
+			GoType: "nerf",
+			Config: &genflags.FlagTypeConfig{},
+		},
+	}
+	if !reflect.DeepEqual(expected, actual) {
+		t.Errorf("expected %#v, got %#v", expected, actual)
+	}
+}
+
+func genFlagType() *genflags.FlagType {
+	return &genflags.FlagType{
+		GoType: "blerf",
+		Config: &genflags.FlagTypeConfig{
+			SkipInterfaces: []string{"fmt.Stringer"},
+			StructFields: []*genflags.FlagStructField{
+				{
+					Name: "Foibles",
+					Type: "int",
+				},
+				{
+					Name: "Hoopled",
+					Type: "bool",
+				},
+			},
+			TypeName:     "YeOldeBlerfFlag",
+			ValuePointer: true,
+		},
+	}
+}
+
+func TestFlagType_StructFields(t *testing.T) {
+	ft := genFlagType()
+
+	sf := ft.StructFields()
+	if 2 != len(sf) {
+		t.Errorf("expected 2 struct fields, got %v", len(sf))
+		return
+	}
+
+	if "Foibles" != sf[0].Name {
+		t.Errorf("expected struct field order to be retained")
+	}
+}
+
+func TestFlagType_ValuePointer(t *testing.T) {
+	ft := genFlagType()
+
+	if !ft.ValuePointer() {
+		t.Errorf("expected ValuePointer to be true")
+		return
+	}
+
+	ft.Config = nil
+
+	if ft.ValuePointer() {
+		t.Errorf("expected ValuePointer to be false")
+	}
+}
+
+func TestFlagType_GenerateFmtStringerInterface(t *testing.T) {
+	ft := genFlagType()
+
+	if ft.GenerateFmtStringerInterface() {
+		t.Errorf("expected GenerateFmtStringerInterface to be false")
+		return
+	}
+
+	ft.Config = nil
+
+	if !ft.GenerateFmtStringerInterface() {
+		t.Errorf("expected GenerateFmtStringerInterface to be true")
+	}
+}
+
+func TestFlagType_GenerateFlagInterface(t *testing.T) {
+	ft := genFlagType()
+
+	if !ft.GenerateFlagInterface() {
+		t.Errorf("expected GenerateFlagInterface to be true")
+		return
+	}
+
+	ft.Config = nil
+
+	if !ft.GenerateFlagInterface() {
+		t.Errorf("expected GenerateFlagInterface to be true")
+	}
+}

mkdocs-requirements.txt

@@ -0,0 +1,5 @@
+mkdocs-git-revision-date-localized-plugin~=1.0
+mkdocs-material-extensions~=1.0
+mkdocs-material~=8.2
+mkdocs~=1.3
+pygments~=2.12

mkdocs.yml

@@ -0,0 +1,62 @@
+# NOTE: the mkdocs dependencies will need to be installed out of
+# band until this whole thing gets more automated:
+#
+#     pip install -r mkdocs-requirements.txt
+#
+
+site_name: urfave/cli
+site_url: https://cli.urfave.org/
+repo_url: https://github.com/urfave/cli
+edit_uri: edit/main/docs/
+nav:
+  - Home: index.md
+  - v2 Manual: v2/index.md
+  - v1 Manual: v1/index.md
+theme:
+  name: material
+  palette:
+    - media: "(prefers-color-scheme: light)"
+      scheme: default
+      toggle:
+        icon: material/brightness-4
+        name: dark mode
+    - media: "(prefers-color-scheme: dark)"
+      scheme: slate
+      toggle:
+        icon: material/brightness-7
+        name: light mode
+plugins:
+  - git-revision-date-localized
+  - search
+# NOTE: this is the recommended configuration from
+# https://squidfunk.github.io/mkdocs-material/setup/extensions/#recommended-configuration
+markdown_extensions:
+  - abbr
+  - admonition
+  - attr_list
+  - def_list
+  - footnotes
+  - meta
+  - md_in_html
+  - toc:
+      permalink: true
+  - pymdownx.arithmatex:
+      generic: true
+  - pymdownx.betterem:
+      smart_enable: all
+  - pymdownx.caret
+  - pymdownx.details
+  - pymdownx.emoji:
+      emoji_index: !!python/name:materialx.emoji.twemoji
+      emoji_generator: !!python/name:materialx.emoji.to_svg
+  - pymdownx.highlight
+  - pymdownx.inlinehilite
+  - pymdownx.keys
+  - pymdownx.mark
+  - pymdownx.smartsymbols
+  - pymdownx.superfences
+  - pymdownx.tabbed:
+      alternate_style: true
+  - pymdownx.tasklist:
+      custom_checkbox: true
+  - pymdownx.tilde

parse.go

@@ -26,9 +26,8 @@ func parseIter(set *flag.FlagSet, ip iterativeParser, args []string, shellComple
 			return err
 		}
 
-		errStr := err.Error()
+		trimmed, trimErr := flagFromError(err)
-		trimmed := strings.TrimPrefix(errStr, "flag provided but not defined: -")
+		if trimErr != nil {
-		if errStr == trimmed {
 			return err
 		}
 
@@ -67,6 +66,19 @@ func parseIter(set *flag.FlagSet, ip iterativeParser, args []string, shellComple
 	}
 }
 
+const providedButNotDefinedErrMsg = "flag provided but not defined: -"
+
+// flagFromError tries to parse a provided flag from an error message. If the
+// parsing fials, it returns the input error and an empty string
+func flagFromError(err error) (string, error) {
+	errStr := err.Error()
+	trimmed := strings.TrimPrefix(errStr, providedButNotDefinedErrMsg)
+	if errStr == trimmed {
+		return "", err
+	}
+	return trimmed, nil
+}
+
 func splitShortOptions(set *flag.FlagSet, arg string) []string {
 	shortFlagsExist := func(s string) bool {
 		for _, c := range s[1:] {

sliceflag.go

@@ -0,0 +1,293 @@
+//go:build go1.18
+// +build go1.18
+
+package cli
+
+import (
+	"flag"
+	"reflect"
+)
+
+type (
+	// SliceFlag extends implementations like StringSliceFlag and IntSliceFlag with support for using slices directly,
+	// as Value and/or Destination.
+	// See also SliceFlagTarget, MultiStringFlag, MultiFloat64Flag, MultiInt64Flag, MultiIntFlag.
+	SliceFlag[T SliceFlagTarget[E], S ~[]E, E any] struct {
+		Target      T
+		Value       S
+		Destination *S
+	}
+
+	// SliceFlagTarget models a target implementation for use with SliceFlag.
+	// The three methods, SetValue, SetDestination, and GetDestination, are necessary to propagate Value and
+	// Destination, where Value is propagated inwards (initially), and Destination is propagated outwards (on every
+	// update).
+	SliceFlagTarget[E any] interface {
+		Flag
+		RequiredFlag
+		DocGenerationFlag
+		VisibleFlag
+		CategorizableFlag
+
+		// SetValue should propagate the given slice to the target, ideally as a new value.
+		// Note that a nil slice should nil/clear any existing value (modelled as ~[]E).
+		SetValue(slice []E)
+		// SetDestination should propagate the given slice to the target, ideally as a new value.
+		// Note that a nil slice should nil/clear any existing value (modelled as ~*[]E).
+		SetDestination(slice []E)
+		// GetDestination should return the current value referenced by any destination, or nil if nil/unset.
+		GetDestination() []E
+	}
+
+	// MultiStringFlag extends StringSliceFlag with support for using slices directly, as Value and/or Destination.
+	// See also SliceFlag.
+	MultiStringFlag = SliceFlag[*StringSliceFlag, []string, string]
+
+	// MultiFloat64Flag extends Float64SliceFlag with support for using slices directly, as Value and/or Destination.
+	// See also SliceFlag.
+	MultiFloat64Flag = SliceFlag[*Float64SliceFlag, []float64, float64]
+
+	// MultiInt64Flag extends Int64SliceFlag with support for using slices directly, as Value and/or Destination.
+	// See also SliceFlag.
+	MultiInt64Flag = SliceFlag[*Int64SliceFlag, []int64, int64]
+
+	// MultiIntFlag extends IntSliceFlag with support for using slices directly, as Value and/or Destination.
+	// See also SliceFlag.
+	MultiIntFlag = SliceFlag[*IntSliceFlag, []int, int]
+
+	flagValueHook struct {
+		value Generic
+		hook  func()
+	}
+)
+
+var (
+	// compile time assertions
+
+	_ SliceFlagTarget[string]  = (*StringSliceFlag)(nil)
+	_ SliceFlagTarget[string]  = (*SliceFlag[*StringSliceFlag, []string, string])(nil)
+	_ SliceFlagTarget[string]  = (*MultiStringFlag)(nil)
+	_ SliceFlagTarget[float64] = (*MultiFloat64Flag)(nil)
+	_ SliceFlagTarget[int64]   = (*MultiInt64Flag)(nil)
+	_ SliceFlagTarget[int]     = (*MultiIntFlag)(nil)
+
+	_ Generic    = (*flagValueHook)(nil)
+	_ Serializer = (*flagValueHook)(nil)
+)
+
+func (x *SliceFlag[T, S, E]) Apply(set *flag.FlagSet) error {
+	x.Target.SetValue(x.convertSlice(x.Value))
+
+	destination := x.Destination
+	if destination == nil {
+		x.Target.SetDestination(nil)
+
+		return x.Target.Apply(set)
+	}
+
+	x.Target.SetDestination(x.convertSlice(*destination))
+
+	return applyFlagValueHook(set, x.Target.Apply, func() {
+		*destination = x.Target.GetDestination()
+	})
+}
+
+func (x *SliceFlag[T, S, E]) convertSlice(slice S) []E {
+	result := make([]E, len(slice))
+	copy(result, slice)
+	return result
+}
+
+func (x *SliceFlag[T, S, E]) SetValue(slice S) {
+	x.Value = slice
+}
+
+func (x *SliceFlag[T, S, E]) SetDestination(slice S) {
+	if slice != nil {
+		x.Destination = &slice
+	} else {
+		x.Destination = nil
+	}
+}
+
+func (x *SliceFlag[T, S, E]) GetDestination() S {
+	if destination := x.Destination; destination != nil {
+		return *destination
+	}
+	return nil
+}
+
+func (x *SliceFlag[T, S, E]) String() string         { return x.Target.String() }
+func (x *SliceFlag[T, S, E]) Names() []string        { return x.Target.Names() }
+func (x *SliceFlag[T, S, E]) IsSet() bool            { return x.Target.IsSet() }
+func (x *SliceFlag[T, S, E]) IsRequired() bool       { return x.Target.IsRequired() }
+func (x *SliceFlag[T, S, E]) TakesValue() bool       { return x.Target.TakesValue() }
+func (x *SliceFlag[T, S, E]) GetUsage() string       { return x.Target.GetUsage() }
+func (x *SliceFlag[T, S, E]) GetValue() string       { return x.Target.GetValue() }
+func (x *SliceFlag[T, S, E]) GetDefaultText() string { return x.Target.GetDefaultText() }
+func (x *SliceFlag[T, S, E]) GetEnvVars() []string   { return x.Target.GetEnvVars() }
+func (x *SliceFlag[T, S, E]) IsVisible() bool        { return x.Target.IsVisible() }
+func (x *SliceFlag[T, S, E]) GetCategory() string    { return x.Target.GetCategory() }
+
+func (x *flagValueHook) Set(value string) error {
+	if err := x.value.Set(value); err != nil {
+		return err
+	}
+	x.hook()
+	return nil
+}
+
+func (x *flagValueHook) String() string {
+	// note: this is necessary due to the way Go's flag package handles defaults
+	isZeroValue := func(f flag.Value, v string) bool {
+		/*
+			https://cs.opensource.google/go/go/+/refs/tags/go1.18.3:src/flag/flag.go;drc=2580d0e08d5e9f979b943758d3c49877fb2324cb;l=453
+
+			Copyright (c) 2009 The Go Authors. All rights reserved.
+			Redistribution and use in source and binary forms, with or without
+			modification, are permitted provided that the following conditions are
+			met:
+			   * Redistributions of source code must retain the above copyright
+			notice, this list of conditions and the following disclaimer.
+			   * Redistributions in binary form must reproduce the above
+			copyright notice, this list of conditions and the following disclaimer
+			in the documentation and/or other materials provided with the
+			distribution.
+			   * Neither the name of Google Inc. nor the names of its
+			contributors may be used to endorse or promote products derived from
+			this software without specific prior written permission.
+			THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+			"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+			LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+			A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+			OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+			SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+			LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+			DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+			THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+			(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+			OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+		*/
+		// Build a zero value of the flag's Value type, and see if the
+		// result of calling its String method equals the value passed in.
+		// This works unless the Value type is itself an interface type.
+		typ := reflect.TypeOf(f)
+		var z reflect.Value
+		if typ.Kind() == reflect.Pointer {
+			z = reflect.New(typ.Elem())
+		} else {
+			z = reflect.Zero(typ)
+		}
+		return v == z.Interface().(flag.Value).String()
+	}
+	if x.value != nil {
+		// only return non-empty if not the same string as returned by the zero value
+		if s := x.value.String(); !isZeroValue(x.value, s) {
+			return s
+		}
+	}
+	return ``
+}
+
+func (x *flagValueHook) Serialize() string {
+	if value, ok := x.value.(Serializer); ok {
+		return value.Serialize()
+	}
+	return x.String()
+}
+
+// applyFlagValueHook wraps calls apply then wraps flags to call a hook function on update and after initial apply.
+func applyFlagValueHook(set *flag.FlagSet, apply func(set *flag.FlagSet) error, hook func()) error {
+	if apply == nil || set == nil || hook == nil {
+		panic(`invalid input`)
+	}
+	var tmp flag.FlagSet
+	if err := apply(&tmp); err != nil {
+		return err
+	}
+	tmp.VisitAll(func(f *flag.Flag) { set.Var(&flagValueHook{value: f.Value, hook: hook}, f.Name, f.Usage) })
+	hook()
+	return nil
+}
+
+// newSliceFlagValue is for implementing SliceFlagTarget.SetValue and SliceFlagTarget.SetDestination.
+// It's e.g. as part of StringSliceFlag.SetValue, using the factory NewStringSlice.
+func newSliceFlagValue[R any, S ~[]E, E any](factory func(defaults ...E) *R, defaults S) *R {
+	if defaults == nil {
+		return nil
+	}
+	return factory(defaults...)
+}
+
+// unwrapFlagValue strips any/all *flagValueHook wrappers.
+func unwrapFlagValue(v flag.Value) flag.Value {
+	for {
+		h, ok := v.(*flagValueHook)
+		if !ok {
+			return v
+		}
+		v = h.value
+	}
+}
+
+// NOTE: the methods below are in this file to make use of the build constraint
+
+func (f *Float64SliceFlag) SetValue(slice []float64) {
+	f.Value = newSliceFlagValue(NewFloat64Slice, slice)
+}
+
+func (f *Float64SliceFlag) SetDestination(slice []float64) {
+	f.Destination = newSliceFlagValue(NewFloat64Slice, slice)
+}
+
+func (f *Float64SliceFlag) GetDestination() []float64 {
+	if destination := f.Destination; destination != nil {
+		return destination.Value()
+	}
+	return nil
+}
+
+func (f *Int64SliceFlag) SetValue(slice []int64) {
+	f.Value = newSliceFlagValue(NewInt64Slice, slice)
+}
+
+func (f *Int64SliceFlag) SetDestination(slice []int64) {
+	f.Destination = newSliceFlagValue(NewInt64Slice, slice)
+}
+
+func (f *Int64SliceFlag) GetDestination() []int64 {
+	if destination := f.Destination; destination != nil {
+		return destination.Value()
+	}
+	return nil
+}
+
+func (f *IntSliceFlag) SetValue(slice []int) {
+	f.Value = newSliceFlagValue(NewIntSlice, slice)
+}
+
+func (f *IntSliceFlag) SetDestination(slice []int) {
+	f.Destination = newSliceFlagValue(NewIntSlice, slice)
+}
+
+func (f *IntSliceFlag) GetDestination() []int {
+	if destination := f.Destination; destination != nil {
+		return destination.Value()
+	}
+	return nil
+}
+
+func (f *StringSliceFlag) SetValue(slice []string) {
+	f.Value = newSliceFlagValue(NewStringSlice, slice)
+}
+
+func (f *StringSliceFlag) SetDestination(slice []string) {
+	f.Destination = newSliceFlagValue(NewStringSlice, slice)
+}
+
+func (f *StringSliceFlag) GetDestination() []string {
+	if destination := f.Destination; destination != nil {
+		return destination.Value()
+	}
+	return nil
+}

sliceflag_pre18.go

@@ -0,0 +1,10 @@
+//go:build !go1.18
+// +build !go1.18
+
+package cli
+
+import (
+	"flag"
+)
+
+func unwrapFlagValue(v flag.Value) flag.Value { return v }

suggestions.go

@@ -0,0 +1,60 @@
+package cli
+
+import (
+	"fmt"
+
+	"github.com/xrash/smetrics"
+)
+
+func jaroWinkler(a, b string) float64 {
+	// magic values are from https://github.com/xrash/smetrics/blob/039620a656736e6ad994090895784a7af15e0b80/jaro-winkler.go#L8
+	const (
+		boostThreshold = 0.7
+		prefixSize     = 4
+	)
+	return smetrics.JaroWinkler(a, b, boostThreshold, prefixSize)
+}
+
+func suggestFlag(flags []Flag, provided string, hideHelp bool) string {
+	distance := 0.0
+	suggestion := ""
+
+	for _, flag := range flags {
+		flagNames := flag.Names()
+		if !hideHelp {
+			flagNames = append(flagNames, HelpFlag.Names()...)
+		}
+		for _, name := range flagNames {
+			newDistance := jaroWinkler(name, provided)
+			if newDistance > distance {
+				distance = newDistance
+				suggestion = name
+			}
+		}
+	}
+
+	if len(suggestion) == 1 {
+		suggestion = "-" + suggestion
+	} else if len(suggestion) > 1 {
+		suggestion = "--" + suggestion
+	}
+
+	return suggestion
+}
+
+// suggestCommand takes a list of commands and a provided string to suggest a
+// command name
+func suggestCommand(commands []*Command, provided string) (suggestion string) {
+	distance := 0.0
+	for _, command := range commands {
+		for _, name := range append(command.Names(), helpName, helpAlias) {
+			newDistance := jaroWinkler(name, provided)
+			if newDistance > distance {
+				distance = newDistance
+				suggestion = name
+			}
+		}
+	}
+
+	return fmt.Sprintf(SuggestDidYouMeanTemplate, suggestion)
+}

suggestions_test.go

@@ -0,0 +1,187 @@
+package cli
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+)
+
+func TestSuggestFlag(t *testing.T) {
+	// Given
+	app := testApp()
+
+	for _, testCase := range []struct {
+		provided, expected string
+	}{
+		{"", ""},
+		{"a", "--another-flag"},
+		{"hlp", "--help"},
+		{"k", ""},
+		{"s", "-s"},
+	} {
+		// When
+		res := suggestFlag(app.Flags, testCase.provided, false)
+
+		// Then
+		expect(t, res, testCase.expected)
+	}
+}
+
+func TestSuggestFlagHideHelp(t *testing.T) {
+	// Given
+	app := testApp()
+
+	// When
+	res := suggestFlag(app.Flags, "hlp", true)
+
+	// Then
+	expect(t, res, "--fl")
+}
+
+func TestSuggestFlagFromError(t *testing.T) {
+	// Given
+	app := testApp()
+
+	for _, testCase := range []struct {
+		command, provided, expected string
+	}{
+		{"", "hel", "--help"},
+		{"", "soccer", "--socket"},
+		{"config", "anot", "--another-flag"},
+	} {
+		// When
+		res, _ := app.suggestFlagFromError(
+			errors.New(providedButNotDefinedErrMsg+testCase.provided),
+			testCase.command,
+		)
+
+		// Then
+		expect(t, res, fmt.Sprintf(SuggestDidYouMeanTemplate+"\n\n", testCase.expected))
+	}
+}
+
+func TestSuggestFlagFromErrorWrongError(t *testing.T) {
+	// Given
+	app := testApp()
+
+	// When
+	_, err := app.suggestFlagFromError(errors.New("invalid"), "")
+
+	// Then
+	expect(t, true, err != nil)
+}
+
+func TestSuggestFlagFromErrorWrongCommand(t *testing.T) {
+	// Given
+	app := testApp()
+
+	// When
+	_, err := app.suggestFlagFromError(
+		errors.New(providedButNotDefinedErrMsg+"flag"),
+		"invalid",
+	)
+
+	// Then
+	expect(t, true, err != nil)
+}
+
+func TestSuggestFlagFromErrorNoSuggestion(t *testing.T) {
+	// Given
+	app := testApp()
+
+	// When
+	_, err := app.suggestFlagFromError(
+		errors.New(providedButNotDefinedErrMsg+""),
+		"",
+	)
+
+	// Then
+	expect(t, true, err != nil)
+}
+
+func TestSuggestCommand(t *testing.T) {
+	// Given
+	app := testApp()
+
+	for _, testCase := range []struct {
+		provided, expected string
+	}{
+		{"", ""},
+		{"conf", "config"},
+		{"i", "i"},
+		{"information", "info"},
+		{"not-existing", "info"},
+	} {
+		// When
+		res := suggestCommand(app.Commands, testCase.provided)
+
+		// Then
+		expect(t, res, fmt.Sprintf(SuggestDidYouMeanTemplate, testCase.expected))
+	}
+}
+
+func ExampleApp_Suggest() {
+	app := &App{
+		Name:                  "greet",
+		Suggest:               true,
+		HideHelp:              true,
+		HideHelpCommand:       true,
+		CustomAppHelpTemplate: "(this space intentionally left blank)\n",
+		Flags: []Flag{
+			&StringFlag{Name: "name", Value: "squirrel", Usage: "a name to say"},
+		},
+		Action: func(cCtx *Context) error {
+			fmt.Printf("Hello %v\n", cCtx.String("name"))
+			return nil
+		},
+	}
+
+	app.Run([]string{"greet", "--nema", "chipmunk"})
+	// Output:
+	// Incorrect Usage. flag provided but not defined: -nema
+	//
+	// Did you mean "--name"?
+	//
+	// (this space intentionally left blank)
+}
+
+func ExampleApp_Suggest_command() {
+	app := &App{
+		Name:                  "greet",
+		Suggest:               true,
+		HideHelp:              true,
+		HideHelpCommand:       true,
+		CustomAppHelpTemplate: "(this space intentionally left blank)\n",
+		Flags: []Flag{
+			&StringFlag{Name: "name", Value: "squirrel", Usage: "a name to say"},
+		},
+		Action: func(cCtx *Context) error {
+			fmt.Printf("Hello %v\n", cCtx.String("name"))
+			return nil
+		},
+		Commands: []*Command{
+			{
+				Name:               "neighbors",
+				CustomHelpTemplate: "(this space intentionally left blank)\n",
+				Flags: []Flag{
+					&BoolFlag{Name: "smiling"},
+				},
+				Action: func(cCtx *Context) error {
+					if cCtx.Bool("smiling") {
+						fmt.Println("😀")
+					}
+					fmt.Println("Hello, neighbors")
+					return nil
+				},
+			},
+		},
+	}
+
+	app.Run([]string{"greet", "neighbors", "--sliming"})
+	// Output:
+	// Incorrect Usage: flag provided but not defined: -sliming
+	//
+	// Did you mean "--smiling"?
+	//
+	// (this space intentionally left blank)
+}

template.go

@@ -4,16 +4,16 @@ package cli
 // cli.go uses text/template to render templates. You can
 // render custom help text by setting this variable.
 var AppHelpTemplate = `NAME:
-   {{.Name}}{{if .Usage}} - {{.Usage}}{{end}}
+   {{$v := offset .Name 6}}{{wrap .Name 3}}{{if .Usage}} - {{wrap .Usage $v}}{{end}}
 
 USAGE:
-   {{if .UsageText}}{{.UsageText | nindent 3 | trim}}{{else}}{{.HelpName}} {{if .VisibleFlags}}[global options]{{end}}{{if .Commands}} command [command options]{{end}} {{if .ArgsUsage}}{{.ArgsUsage}}{{else}}[arguments...]{{end}}{{end}}{{if .Version}}{{if not .HideVersion}}
+   {{if .UsageText}}{{wrap .UsageText 3}}{{else}}{{.HelpName}} {{if .VisibleFlags}}[global options]{{end}}{{if .Commands}} command [command options]{{end}} {{if .ArgsUsage}}{{.ArgsUsage}}{{else}}[arguments...]{{end}}{{end}}{{if .Version}}{{if not .HideVersion}}
 
 VERSION:
    {{.Version}}{{end}}{{end}}{{if .Description}}
 
 DESCRIPTION:
-   {{.Description | nindent 3 | trim}}{{end}}{{if len .Authors}}
+   {{wrap .Description 3}}{{end}}{{if len .Authors}}
 
 AUTHOR{{with $length := len .Authors}}{{if ne 1 $length}}S{{end}}{{end}}:
    {{range $index, $author := .Authors}}{{if $index}}
@@ -22,34 +22,44 @@ AUTHOR{{with $length := len .Authors}}{{if ne 1 $length}}S{{end}}{{end}}:
 COMMANDS:{{range .VisibleCategories}}{{if .Name}}
    {{.Name}}:{{range .VisibleCommands}}
      {{join .Names ", "}}{{"\t"}}{{.Usage}}{{end}}{{else}}{{range .VisibleCommands}}
-   {{join .Names ", "}}{{"\t"}}{{.Usage}}{{end}}{{end}}{{end}}{{end}}{{if .VisibleFlags}}
+   {{join .Names ", "}}{{"\t"}}{{.Usage}}{{end}}{{end}}{{end}}{{end}}{{if .VisibleFlagCategories}}
+
+GLOBAL OPTIONS:{{range .VisibleFlagCategories}}
+   {{if .Name}}{{.Name}}
+   {{end}}{{range .Flags}}{{.}}
+   {{end}}{{end}}{{else}}{{if .VisibleFlags}}
 
 GLOBAL OPTIONS:
    {{range $index, $option := .VisibleFlags}}{{if $index}}
-   {{end}}{{$option}}{{end}}{{end}}{{if .Copyright}}
+   {{end}}{{wrap $option.String 6}}{{end}}{{end}}{{end}}{{if .Copyright}}
 
 COPYRIGHT:
-   {{.Copyright}}{{end}}
+   {{wrap .Copyright 3}}{{end}}
 `
 
 // CommandHelpTemplate is the text template for the command help topic.
 // cli.go uses text/template to render templates. You can
 // render custom help text by setting this variable.
 var CommandHelpTemplate = `NAME:
-   {{.HelpName}} - {{.Usage}}
+   {{$v := offset .HelpName 6}}{{wrap .HelpName 3}}{{if .Usage}} - {{wrap .Usage $v}}{{end}}
 
 USAGE:
-   {{if .UsageText}}{{.UsageText | nindent 3 | trim}}{{else}}{{.HelpName}}{{if .VisibleFlags}} [command options]{{end}} {{if .ArgsUsage}}{{.ArgsUsage}}{{else}}[arguments...]{{end}}{{end}}{{if .Category}}
+   {{if .UsageText}}{{wrap .UsageText 3}}{{else}}{{.HelpName}}{{if .VisibleFlags}} [command options]{{end}} {{if .ArgsUsage}}{{.ArgsUsage}}{{else}}[arguments...]{{end}}{{end}}{{if .Category}}
 
 CATEGORY:
    {{.Category}}{{end}}{{if .Description}}
 
 DESCRIPTION:
-   {{.Description | nindent 3 | trim}}{{end}}{{if .VisibleFlags}}
+   {{wrap .Description 3}}{{end}}{{if .VisibleFlagCategories}}
+
+OPTIONS:{{range .VisibleFlagCategories}}
+   {{if .Name}}{{.Name}}
+   {{end}}{{range .Flags}}{{.}}
+   {{end}}{{end}}{{else}}{{if .VisibleFlags}}
 
 OPTIONS:
    {{range .VisibleFlags}}{{.}}
-   {{end}}{{end}}
+   {{end}}{{end}}{{end}}
 `
 
 // SubcommandHelpTemplate is the text template for the subcommand help topic.
@@ -59,10 +69,10 @@ var SubcommandHelpTemplate = `NAME:
    {{.HelpName}} - {{.Usage}}
 
 USAGE:
-   {{if .UsageText}}{{.UsageText | nindent 3 | trim}}{{else}}{{.HelpName}} command{{if .VisibleFlags}} [command options]{{end}} {{if .ArgsUsage}}{{.ArgsUsage}}{{else}}[arguments...]{{end}}{{end}}{{if .Description}}
+   {{if .UsageText}}{{wrap .UsageText 3}}{{else}}{{.HelpName}} command{{if .VisibleFlags}} [command options]{{end}} {{if .ArgsUsage}}{{.ArgsUsage}}{{else}}[arguments...]{{end}}{{end}}{{if .Description}}
 
 DESCRIPTION:
-   {{.Description | nindent 3 | trim}}{{end}}
+   {{wrap .Description 3}}{{end}}
 
 COMMANDS:{{range .VisibleCategories}}{{if .Name}}
    {{.Name}}:{{range .VisibleCommands}}

testdata/empty.yml

@@ -0,0 +1 @@
+# empty file

zz_generated.flags.go

@@ -0,0 +1,674 @@
+// WARNING: this file is generated. DO NOT EDIT
+
+package cli
+
+import "time"
+
+// Float64SliceFlag is a flag with type *Float64Slice
+type Float64SliceFlag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       *Float64Slice
+	Destination *Float64Slice
+
+	Aliases []string
+	EnvVars []string
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *Float64SliceFlag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *Float64SliceFlag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *Float64SliceFlag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *Float64SliceFlag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// GenericFlag is a flag with type Generic
+type GenericFlag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       Generic
+	Destination *Generic
+
+	Aliases []string
+	EnvVars []string
+
+	TakesFile bool
+}
+
+// String returns a readable representation of this value (for usage defaults)
+func (f *GenericFlag) String() string {
+	return FlagStringer(f)
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *GenericFlag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *GenericFlag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *GenericFlag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *GenericFlag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// Int64SliceFlag is a flag with type *Int64Slice
+type Int64SliceFlag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       *Int64Slice
+	Destination *Int64Slice
+
+	Aliases []string
+	EnvVars []string
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *Int64SliceFlag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *Int64SliceFlag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *Int64SliceFlag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *Int64SliceFlag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// IntSliceFlag is a flag with type *IntSlice
+type IntSliceFlag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       *IntSlice
+	Destination *IntSlice
+
+	Aliases []string
+	EnvVars []string
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *IntSliceFlag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *IntSliceFlag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *IntSliceFlag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *IntSliceFlag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// PathFlag is a flag with type Path
+type PathFlag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       Path
+	Destination *Path
+
+	Aliases []string
+	EnvVars []string
+
+	TakesFile bool
+}
+
+// String returns a readable representation of this value (for usage defaults)
+func (f *PathFlag) String() string {
+	return FlagStringer(f)
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *PathFlag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *PathFlag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *PathFlag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *PathFlag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// StringSliceFlag is a flag with type *StringSlice
+type StringSliceFlag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       *StringSlice
+	Destination *StringSlice
+
+	Aliases []string
+	EnvVars []string
+
+	TakesFile bool
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *StringSliceFlag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *StringSliceFlag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *StringSliceFlag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *StringSliceFlag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// TimestampFlag is a flag with type *Timestamp
+type TimestampFlag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       *Timestamp
+	Destination *Timestamp
+
+	Aliases []string
+	EnvVars []string
+
+	Layout string
+
+	Timezone *time.Location
+}
+
+// String returns a readable representation of this value (for usage defaults)
+func (f *TimestampFlag) String() string {
+	return FlagStringer(f)
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *TimestampFlag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *TimestampFlag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *TimestampFlag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *TimestampFlag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// BoolFlag is a flag with type bool
+type BoolFlag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       bool
+	Destination *bool
+
+	Aliases []string
+	EnvVars []string
+}
+
+// String returns a readable representation of this value (for usage defaults)
+func (f *BoolFlag) String() string {
+	return FlagStringer(f)
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *BoolFlag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *BoolFlag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *BoolFlag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *BoolFlag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// Float64Flag is a flag with type float64
+type Float64Flag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       float64
+	Destination *float64
+
+	Aliases []string
+	EnvVars []string
+}
+
+// String returns a readable representation of this value (for usage defaults)
+func (f *Float64Flag) String() string {
+	return FlagStringer(f)
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *Float64Flag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *Float64Flag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *Float64Flag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *Float64Flag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// IntFlag is a flag with type int
+type IntFlag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       int
+	Destination *int
+
+	Aliases []string
+	EnvVars []string
+}
+
+// String returns a readable representation of this value (for usage defaults)
+func (f *IntFlag) String() string {
+	return FlagStringer(f)
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *IntFlag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *IntFlag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *IntFlag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *IntFlag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// Int64Flag is a flag with type int64
+type Int64Flag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       int64
+	Destination *int64
+
+	Aliases []string
+	EnvVars []string
+}
+
+// String returns a readable representation of this value (for usage defaults)
+func (f *Int64Flag) String() string {
+	return FlagStringer(f)
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *Int64Flag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *Int64Flag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *Int64Flag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *Int64Flag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// StringFlag is a flag with type string
+type StringFlag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       string
+	Destination *string
+
+	Aliases []string
+	EnvVars []string
+
+	TakesFile bool
+}
+
+// String returns a readable representation of this value (for usage defaults)
+func (f *StringFlag) String() string {
+	return FlagStringer(f)
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *StringFlag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *StringFlag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *StringFlag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *StringFlag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// DurationFlag is a flag with type time.Duration
+type DurationFlag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       time.Duration
+	Destination *time.Duration
+
+	Aliases []string
+	EnvVars []string
+}
+
+// String returns a readable representation of this value (for usage defaults)
+func (f *DurationFlag) String() string {
+	return FlagStringer(f)
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *DurationFlag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *DurationFlag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *DurationFlag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *DurationFlag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// UintFlag is a flag with type uint
+type UintFlag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       uint
+	Destination *uint
+
+	Aliases []string
+	EnvVars []string
+}
+
+// String returns a readable representation of this value (for usage defaults)
+func (f *UintFlag) String() string {
+	return FlagStringer(f)
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *UintFlag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *UintFlag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *UintFlag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *UintFlag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// Uint64Flag is a flag with type uint64
+type Uint64Flag struct {
+	Name string
+
+	Category    string
+	DefaultText string
+	FilePath    string
+	Usage       string
+
+	Required   bool
+	Hidden     bool
+	HasBeenSet bool
+
+	Value       uint64
+	Destination *uint64
+
+	Aliases []string
+	EnvVars []string
+}
+
+// String returns a readable representation of this value (for usage defaults)
+func (f *Uint64Flag) String() string {
+	return FlagStringer(f)
+}
+
+// IsSet returns whether or not the flag has been set through env or file
+func (f *Uint64Flag) IsSet() bool {
+	return f.HasBeenSet
+}
+
+// Names returns the names of the flag
+func (f *Uint64Flag) Names() []string {
+	return FlagNames(f.Name, f.Aliases)
+}
+
+// IsRequired returns whether or not the flag is required
+func (f *Uint64Flag) IsRequired() bool {
+	return f.Required
+}
+
+// IsVisible returns true if the flag is not hidden, otherwise false
+func (f *Uint64Flag) IsVisible() bool {
+	return !f.Hidden
+}
+
+// vim:ro

zz_generated.flags_test.go

@@ -0,0 +1,363 @@
+// WARNING: this file is generated. DO NOT EDIT
+
+package cli_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/urfave/cli/v2"
+)
+
+func TestFloat64SliceFlag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.Float64SliceFlag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestFloat64SliceFlag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.Float64SliceFlag{}
+
+	_ = f.IsRequired()
+}
+
+func TestFloat64SliceFlag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.Float64SliceFlag{}
+
+	_ = f.IsVisible()
+}
+
+func TestGenericFlag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.GenericFlag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestGenericFlag_SatisfiesFmtStringerInterface(t *testing.T) {
+	var f fmt.Stringer = &cli.GenericFlag{}
+
+	_ = f.String()
+}
+
+func TestGenericFlag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.GenericFlag{}
+
+	_ = f.IsRequired()
+}
+
+func TestGenericFlag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.GenericFlag{}
+
+	_ = f.IsVisible()
+}
+
+func TestInt64SliceFlag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.Int64SliceFlag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestInt64SliceFlag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.Int64SliceFlag{}
+
+	_ = f.IsRequired()
+}
+
+func TestInt64SliceFlag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.Int64SliceFlag{}
+
+	_ = f.IsVisible()
+}
+
+func TestIntSliceFlag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.IntSliceFlag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestIntSliceFlag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.IntSliceFlag{}
+
+	_ = f.IsRequired()
+}
+
+func TestIntSliceFlag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.IntSliceFlag{}
+
+	_ = f.IsVisible()
+}
+
+func TestPathFlag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.PathFlag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestPathFlag_SatisfiesFmtStringerInterface(t *testing.T) {
+	var f fmt.Stringer = &cli.PathFlag{}
+
+	_ = f.String()
+}
+
+func TestPathFlag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.PathFlag{}
+
+	_ = f.IsRequired()
+}
+
+func TestPathFlag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.PathFlag{}
+
+	_ = f.IsVisible()
+}
+
+func TestStringSliceFlag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.StringSliceFlag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestStringSliceFlag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.StringSliceFlag{}
+
+	_ = f.IsRequired()
+}
+
+func TestStringSliceFlag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.StringSliceFlag{}
+
+	_ = f.IsVisible()
+}
+
+func TestTimestampFlag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.TimestampFlag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestTimestampFlag_SatisfiesFmtStringerInterface(t *testing.T) {
+	var f fmt.Stringer = &cli.TimestampFlag{}
+
+	_ = f.String()
+}
+
+func TestTimestampFlag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.TimestampFlag{}
+
+	_ = f.IsRequired()
+}
+
+func TestTimestampFlag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.TimestampFlag{}
+
+	_ = f.IsVisible()
+}
+
+func TestBoolFlag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.BoolFlag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestBoolFlag_SatisfiesFmtStringerInterface(t *testing.T) {
+	var f fmt.Stringer = &cli.BoolFlag{}
+
+	_ = f.String()
+}
+
+func TestBoolFlag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.BoolFlag{}
+
+	_ = f.IsRequired()
+}
+
+func TestBoolFlag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.BoolFlag{}
+
+	_ = f.IsVisible()
+}
+
+func TestFloat64Flag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.Float64Flag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestFloat64Flag_SatisfiesFmtStringerInterface(t *testing.T) {
+	var f fmt.Stringer = &cli.Float64Flag{}
+
+	_ = f.String()
+}
+
+func TestFloat64Flag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.Float64Flag{}
+
+	_ = f.IsRequired()
+}
+
+func TestFloat64Flag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.Float64Flag{}
+
+	_ = f.IsVisible()
+}
+
+func TestIntFlag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.IntFlag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestIntFlag_SatisfiesFmtStringerInterface(t *testing.T) {
+	var f fmt.Stringer = &cli.IntFlag{}
+
+	_ = f.String()
+}
+
+func TestIntFlag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.IntFlag{}
+
+	_ = f.IsRequired()
+}
+
+func TestIntFlag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.IntFlag{}
+
+	_ = f.IsVisible()
+}
+
+func TestInt64Flag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.Int64Flag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestInt64Flag_SatisfiesFmtStringerInterface(t *testing.T) {
+	var f fmt.Stringer = &cli.Int64Flag{}
+
+	_ = f.String()
+}
+
+func TestInt64Flag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.Int64Flag{}
+
+	_ = f.IsRequired()
+}
+
+func TestInt64Flag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.Int64Flag{}
+
+	_ = f.IsVisible()
+}
+
+func TestStringFlag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.StringFlag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestStringFlag_SatisfiesFmtStringerInterface(t *testing.T) {
+	var f fmt.Stringer = &cli.StringFlag{}
+
+	_ = f.String()
+}
+
+func TestStringFlag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.StringFlag{}
+
+	_ = f.IsRequired()
+}
+
+func TestStringFlag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.StringFlag{}
+
+	_ = f.IsVisible()
+}
+
+func TestDurationFlag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.DurationFlag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestDurationFlag_SatisfiesFmtStringerInterface(t *testing.T) {
+	var f fmt.Stringer = &cli.DurationFlag{}
+
+	_ = f.String()
+}
+
+func TestDurationFlag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.DurationFlag{}
+
+	_ = f.IsRequired()
+}
+
+func TestDurationFlag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.DurationFlag{}
+
+	_ = f.IsVisible()
+}
+
+func TestUintFlag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.UintFlag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestUintFlag_SatisfiesFmtStringerInterface(t *testing.T) {
+	var f fmt.Stringer = &cli.UintFlag{}
+
+	_ = f.String()
+}
+
+func TestUintFlag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.UintFlag{}
+
+	_ = f.IsRequired()
+}
+
+func TestUintFlag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.UintFlag{}
+
+	_ = f.IsVisible()
+}
+
+func TestUint64Flag_SatisfiesFlagInterface(t *testing.T) {
+	var f cli.Flag = &cli.Uint64Flag{}
+
+	_ = f.IsSet()
+	_ = f.Names()
+}
+
+func TestUint64Flag_SatisfiesFmtStringerInterface(t *testing.T) {
+	var f fmt.Stringer = &cli.Uint64Flag{}
+
+	_ = f.String()
+}
+
+func TestUint64Flag_SatisfiesRequiredFlagInterface(t *testing.T) {
+	var f cli.RequiredFlag = &cli.Uint64Flag{}
+
+	_ = f.IsRequired()
+}
+
+func TestUint64Flag_SatisfiesVisibleFlagInterface(t *testing.T) {
+	var f cli.VisibleFlag = &cli.Uint64Flag{}
+
+	_ = f.IsVisible()
+}
+
+// vim:ro