Merge branch 'master' into required_flags

flag.go

@@ -3,49 +3,102 @@ package cli
 import (
 	"flag"
 	"fmt"
-	"os"
+	"io/ioutil"
+	"reflect"
+	"runtime"
 	"strconv"
 	"strings"
+	"syscall"
 	"time"
 )
 
-// This flag enables bash-completion for all commands and subcommands
-var BashCompletionFlag = BoolFlag{
-	Name: "generate-bash-completion",
+const defaultPlaceholder = "value"
+
+// BashCompletionFlag enables bash-completion for all commands and subcommands
+var BashCompletionFlag Flag = BoolFlag{
+	Name:   "generate-bash-completion",
+	Hidden: true,
 }
 
-// This flag prints the version for the application
-var VersionFlag = BoolFlag{
+// VersionFlag prints the version for the application
+var VersionFlag Flag = BoolFlag{
 	Name:  "version, v",
 	Usage: "print the version",
 }
 
-// This flag prints the help for all commands and subcommands
+// HelpFlag prints the help for all commands and subcommands
 // Set to the zero value (BoolFlag{}) to disable flag -- keeps subcommand
 // unless HideHelp is set to true)
-var HelpFlag = BoolFlag{
+var HelpFlag Flag = BoolFlag{
 	Name:  "help, h",
 	Usage: "show help",
 }
 
+// FlagStringer converts a flag definition to a string. This is used by help
+// to display a flag.
+var FlagStringer FlagStringFunc = stringifyFlag
+
+// FlagNamePrefixer converts a full flag name and its placeholder into the help
+// message flag prefix. This is used by the default FlagStringer.
+var FlagNamePrefixer FlagNamePrefixFunc = prefixedNames
+
+// FlagEnvHinter annotates flag help message with the environment variable
+// details. This is used by the default FlagStringer.
+var FlagEnvHinter FlagEnvHintFunc = withEnvHint
+
+// FlagFileHinter annotates flag help message with the environment variable
+// details. This is used by the default FlagStringer.
+var FlagFileHinter FlagFileHintFunc = withFileHint
+
+// FlagsByName is a slice of Flag.
+type FlagsByName []Flag
+
+func (f FlagsByName) Len() int {
+	return len(f)
+}
+
+func (f FlagsByName) Less(i, j int) bool {
+	return lexicographicLess(f[i].GetName(), f[j].GetName())
+}
+
+func (f FlagsByName) Swap(i, j int) {
+	f[i], f[j] = f[j], f[i]
+}
+
 // Flag is a common interface related to parsing flags in cli.
-// For more advanced flag parsing techniques, it is recomended that
+// For more advanced flag parsing techniques, it is recommended that
 // this interface be implemented.
 type Flag interface {
 	fmt.Stringer
 	// Apply Flag settings to the given flag set
 	Apply(*flag.FlagSet)
-	getName() string
 	IsRequired() bool
+	GetName() string
 }
 
-func flagSet(name string, flags []Flag) *flag.FlagSet {
+// errorableFlag is an interface that allows us to return errors during apply
+// it allows flags defined in this library to return errors in a fashion backwards compatible
+// TODO remove in v2 and modify the existing Flag interface to return errors
+type errorableFlag interface {
+	Flag
+
+	ApplyWithError(*flag.FlagSet) error
+}
+
+func flagSet(name string, flags []Flag) (*flag.FlagSet, error) {
 	set := flag.NewFlagSet(name, flag.ContinueOnError)
 
 	for _, f := range flags {
-		f.Apply(set)
+		//TODO remove in v2 when errorableFlag is removed
+		if ef, ok := f.(errorableFlag); ok {
+			if err := ef.ApplyWithError(set); err != nil {
+				return nil, err
+			}
+		} else {
+			f.Apply(set)
+		}
 	}
-	return set
+	return set, nil
 }
 
 func eachName(longName string, fn func(string)) {
@@ -80,42 +133,47 @@ func (f GenericFlag) String() string {
 
 // Apply takes the flagset and calls Set on the generic flag with the value
 // provided by the user for parsing by the flag
+// Ignores parsing errors
 func (f GenericFlag) Apply(set *flag.FlagSet) {
+	f.ApplyWithError(set)
+}
+
+// ApplyWithError 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) ApplyWithError(set *flag.FlagSet) error {
 	val := f.Value
-	if f.EnvVar != "" {
-		for _, envVar := range strings.Split(f.EnvVar, ",") {
-			envVar = strings.TrimSpace(envVar)
-			if envVal := os.Getenv(envVar); envVal != "" {
-				val.Set(envVal)
-				break
-			}
+	if fileEnvVal, ok := flagFromFileEnv(f.FilePath, f.EnvVar); ok {
+		if err := val.Set(fileEnvVal); err != nil {
+			return fmt.Errorf("could not parse %s as value for flag %s: %s", fileEnvVal, f.Name, err)
 		}
 	}
 
 	eachName(f.Name, func(name string) {
 		set.Var(f.Value, name, f.Usage)
 	})
-}
 
-func (f GenericFlag) getName() string {
-	return f.Name
+	return nil
 }
 
 func (f GenericFlag) IsRequired() bool {
 	return f.Required
 }
 
+// StringSlice is an opaque type for []string to satisfy flag.Value and flag.Getter
 type StringSlice []string
 
+// Set appends the string value to the list of values
 func (f *StringSlice) Set(value string) error {
 	*f = append(*f, value)
 	return nil
 }
 
+// String returns a readable representation of this value (for usage defaults)
 func (f *StringSlice) String() string {
 	return fmt.Sprintf("%s", *f)
 }
 
+// Value returns the slice of strings set by this flag
 func (f *StringSlice) Value() []string {
 	return *f
 }
@@ -134,52 +192,67 @@ func (f StringSliceFlag) String() string {
 	return withHints(f.EnvVar, f.Required, fmt.Sprintf("%s [%v]\t%v", prefixedNames(f.Name), pref+firstName+" option "+pref+firstName+" option", f.Usage))
 }
 
+// Get returns the slice of strings set by this flag
+func (f *StringSlice) Get() interface{} {
+	return *f
+}
+
+// Apply populates the flag given the flag set and environment
+// Ignores errors
 func (f StringSliceFlag) Apply(set *flag.FlagSet) {
-	if f.EnvVar != "" {
-		for _, envVar := range strings.Split(f.EnvVar, ",") {
-			envVar = strings.TrimSpace(envVar)
-			if envVal := os.Getenv(envVar); envVal != "" {
-				newVal := &StringSlice{}
-				for _, s := range strings.Split(envVal, ",") {
-					s = strings.TrimSpace(s)
-					newVal.Set(s)
-				}
-				f.Value = newVal
-				break
+	f.ApplyWithError(set)
+}
+
+// ApplyWithError populates the flag given the flag set and environment
+func (f StringSliceFlag) ApplyWithError(set *flag.FlagSet) error {
+	if envVal, ok := flagFromFileEnv(f.FilePath, f.EnvVar); ok {
+		newVal := &StringSlice{}
+		for _, s := range strings.Split(envVal, ",") {
+			s = strings.TrimSpace(s)
+			if err := newVal.Set(s); err != nil {
+				return fmt.Errorf("could not parse %s as string value for flag %s: %s", envVal, f.Name, err)
 			}
 		}
+		if f.Value == nil {
+			f.Value = newVal
+		} else {
+			*f.Value = *newVal
+		}
 	}
 
 	eachName(f.Name, func(name string) {
+		if f.Value == nil {
+			f.Value = &StringSlice{}
+		}
 		set.Var(f.Value, name, f.Usage)
 	})
-}
 
-func (f StringSliceFlag) getName() string {
-	return f.Name
+	return nil
 }
 
 func (f StringSliceFlag) IsRequired() bool {
 	return f.Required
 }
 
+// IntSlice is an opaque type for []int to satisfy flag.Value and flag.Getter
 type IntSlice []int
 
+// Set parses the value into an integer and appends it to the list of values
 func (f *IntSlice) Set(value string) error {
-
 	tmp, err := strconv.Atoi(value)
 	if err != nil {
 		return err
-	} else {
-		*f = append(*f, tmp)
 	}
+	*f = append(*f, tmp)
 	return nil
 }
 
+// String returns a readable representation of this value (for usage defaults)
 func (f *IntSlice) String() string {
-	return fmt.Sprintf("%d", *f)
+	return fmt.Sprintf("%#v", *f)
 }
 
+// Value returns the slice of ints set by this flag
 func (f *IntSlice) Value() []int {
 	return *f
 }
@@ -198,32 +271,60 @@ func (f IntSliceFlag) String() string {
 	return withHints(f.EnvVar, f.Required, fmt.Sprintf("%s [%v]\t%v", prefixedNames(f.Name), pref+firstName+" option "+pref+firstName+" option", f.Usage))
 }
 
+// Get returns the slice of ints set by this flag
+func (f *IntSlice) Get() interface{} {
+	return *f
+}
+
+// Apply populates the flag given the flag set and environment
+// Ignores errors
 func (f IntSliceFlag) Apply(set *flag.FlagSet) {
-	if f.EnvVar != "" {
-		for _, envVar := range strings.Split(f.EnvVar, ",") {
-			envVar = strings.TrimSpace(envVar)
-			if envVal := os.Getenv(envVar); envVal != "" {
-				newVal := &IntSlice{}
-				for _, s := range strings.Split(envVal, ",") {
-					s = strings.TrimSpace(s)
-					err := newVal.Set(s)
-					if err != nil {
-						fmt.Fprintf(os.Stderr, err.Error())
-					}
-				}
-				f.Value = newVal
-				break
+	f.ApplyWithError(set)
+}
+
+// ApplyWithError populates the flag given the flag set and environment
+func (f IntSliceFlag) ApplyWithError(set *flag.FlagSet) error {
+	if envVal, ok := flagFromFileEnv(f.FilePath, f.EnvVar); ok {
+		newVal := &IntSlice{}
+		for _, s := range strings.Split(envVal, ",") {
+			s = strings.TrimSpace(s)
+			if err := newVal.Set(s); err != nil {
+				return fmt.Errorf("could not parse %s as int slice value for flag %s: %s", envVal, f.Name, err)
 			}
 		}
+		if f.Value == nil {
+			f.Value = newVal
+		} else {
+			*f.Value = *newVal
+		}
 	}
 
 	eachName(f.Name, func(name string) {
+		if f.Value == nil {
+			f.Value = &IntSlice{}
+		}
 		set.Var(f.Value, name, f.Usage)
 	})
+
+	return nil
 }
 
-func (f IntSliceFlag) getName() string {
-	return f.Name
+// Int64Slice is an opaque type for []int to satisfy flag.Value and flag.Getter
+type Int64Slice []int64
+
+// Set parses the value into an integer and appends it to the list of values
+func (f *Int64Slice) Set(value string) error {
+	tmp, err := strconv.ParseInt(value, 10, 64)
+	if err != nil {
+		return err
+	}
+	*f = append(*f, tmp)
+	return nil
+}
+
+// String returns a readable representation of this value (for usage defaults)
+func (f *Int64Slice) String() string {
+	return fmt.Sprintf("%#v", *f)
 }
 
 func (f IntSliceFlag) IsRequired() bool {
@@ -241,28 +342,52 @@ func (f BoolFlag) String() string {
 	return withHints(f.EnvVar, f.Required, fmt.Sprintf("%s\t%v", prefixedNames(f.Name), f.Usage))
 }
 
-func (f BoolFlag) Apply(set *flag.FlagSet) {
-	val := false
-	if f.EnvVar != "" {
-		for _, envVar := range strings.Split(f.EnvVar, ",") {
-			envVar = strings.TrimSpace(envVar)
-			if envVal := os.Getenv(envVar); envVal != "" {
-				envValBool, err := strconv.ParseBool(envVal)
-				if err == nil {
-					val = envValBool
-				}
-				break
+// Value returns the slice of ints set by this flag
+func (f *Int64Slice) Value() []int64 {
+	return *f
+}
+
+// Get returns the slice of ints set by this flag
+func (f *Int64Slice) Get() interface{} {
+	return *f
+}
+
+// Apply populates the flag given the flag set and environment
+// Ignores errors
+func (f Int64SliceFlag) Apply(set *flag.FlagSet) {
+	f.ApplyWithError(set)
+}
+
+// ApplyWithError populates the flag given the flag set and environment
+func (f Int64SliceFlag) ApplyWithError(set *flag.FlagSet) error {
+	if envVal, ok := flagFromFileEnv(f.FilePath, f.EnvVar); ok {
+		newVal := &Int64Slice{}
+		for _, s := range strings.Split(envVal, ",") {
+			s = strings.TrimSpace(s)
+			if err := newVal.Set(s); err != nil {
+				return fmt.Errorf("could not parse %s as int64 slice value for flag %s: %s", envVal, f.Name, err)
 			}
 		}
+		if f.Value == nil {
+			f.Value = newVal
+		} else {
+			*f.Value = *newVal
+		}
 	}
 
 	eachName(f.Name, func(name string) {
-		set.Bool(name, val, f.Usage)
+		if f.Value == nil {
+			f.Value = &Int64Slice{}
+		}
+		set.Var(f.Value, name, f.Usage)
 	})
+	return nil
 }
 
-func (f BoolFlag) getName() string {
-	return f.Name
+// Apply populates the flag given the flag set and environment
+// Ignores errors
+func (f BoolFlag) Apply(set *flag.FlagSet) {
+	f.ApplyWithError(set)
 }
 
 func (f BoolFlag) IsRequired() bool {
@@ -280,28 +405,63 @@ func (f BoolTFlag) String() string {
 	return withHints(f.EnvVar, f.Required, fmt.Sprintf("%s\t%v", prefixedNames(f.Name), f.Usage))
 }
 
-func (f BoolTFlag) Apply(set *flag.FlagSet) {
-	val := true
-	if f.EnvVar != "" {
-		for _, envVar := range strings.Split(f.EnvVar, ",") {
-			envVar = strings.TrimSpace(envVar)
-			if envVal := os.Getenv(envVar); envVal != "" {
-				envValBool, err := strconv.ParseBool(envVal)
-				if err == nil {
-					val = envValBool
-					break
-				}
+// ApplyWithError populates the flag given the flag set and environment
+func (f BoolFlag) ApplyWithError(set *flag.FlagSet) error {
+	val := false
+	if envVal, ok := flagFromFileEnv(f.FilePath, f.EnvVar); ok {
+		if envVal == "" {
+			val = false
+		} else {
+			envValBool, err := strconv.ParseBool(envVal)
+			if err != nil {
+				return fmt.Errorf("could not parse %s as bool value for flag %s: %s", envVal, f.Name, err)
 			}
+			val = envValBool
 		}
 	}
 
 	eachName(f.Name, func(name string) {
+		if f.Destination != nil {
+			set.BoolVar(f.Destination, name, val, f.Usage)
+			return
+		}
 		set.Bool(name, val, f.Usage)
 	})
+
+	return nil
 }
 
-func (f BoolTFlag) getName() string {
-	return f.Name
+// Apply populates the flag given the flag set and environment
+// Ignores errors
+func (f BoolTFlag) Apply(set *flag.FlagSet) {
+	f.ApplyWithError(set)
+}
+
+// ApplyWithError populates the flag given the flag set and environment
+func (f BoolTFlag) ApplyWithError(set *flag.FlagSet) error {
+	val := true
+
+	if envVal, ok := flagFromFileEnv(f.FilePath, f.EnvVar); ok {
+		if envVal == "" {
+			val = false
+		} else {
+			envValBool, err := strconv.ParseBool(envVal)
+			if err != nil {
+				return fmt.Errorf("could not parse %s as bool value for flag %s: %s", envVal, f.Name, err)
+			}
+			val = envValBool
+		}
+	}
+
+	eachName(f.Name, func(name string) {
+		if f.Destination != nil {
+			set.BoolVar(f.Destination, name, val, f.Usage)
+			return
+		}
+		set.Bool(name, val, f.Usage)
+	})
+
+	return nil
 }
 
 func (f BoolTFlag) IsRequired() bool {
@@ -316,37 +476,60 @@ type StringFlag struct {
 	Required bool
 }
 
-func (f StringFlag) String() string {
-	var fmtString string
-	fmtString = "%s %v\t%v"
-
-	if len(f.Value) > 0 {
-		fmtString = "%s \"%v\"\t%v"
-	} else {
-		fmtString = "%s %v\t%v"
-	}
-
-	return withHints(f.EnvVar, f.Required, fmt.Sprintf(fmtString, prefixedNames(f.Name), f.Value, f.Usage))
+// Apply populates the flag given the flag set and environment
+// Ignores errors
+func (f StringFlag) Apply(set *flag.FlagSet) {
+	f.ApplyWithError(set)
 }
 
-func (f StringFlag) Apply(set *flag.FlagSet) {
-	if f.EnvVar != "" {
-		for _, envVar := range strings.Split(f.EnvVar, ",") {
-			envVar = strings.TrimSpace(envVar)
-			if envVal := os.Getenv(envVar); envVal != "" {
-				f.Value = envVal
-				break
-			}
-		}
+// ApplyWithError populates the flag given the flag set and environment
+func (f StringFlag) ApplyWithError(set *flag.FlagSet) error {
+	if envVal, ok := flagFromFileEnv(f.FilePath, f.EnvVar); ok {
+		f.Value = envVal
 	}
 
 	eachName(f.Name, func(name string) {
+		if f.Destination != nil {
+			set.StringVar(f.Destination, name, f.Value, f.Usage)
+			return
+		}
 		set.String(name, f.Value, f.Usage)
 	})
+
+	return nil
 }
 
-func (f StringFlag) getName() string {
-	return f.Name
+// Apply populates the flag given the flag set and environment
+// Ignores errors
+func (f IntFlag) Apply(set *flag.FlagSet) {
+	f.ApplyWithError(set)
+}
+
+// ApplyWithError populates the flag given the flag set and environment
+func (f IntFlag) ApplyWithError(set *flag.FlagSet) error {
+	if envVal, ok := flagFromFileEnv(f.FilePath, f.EnvVar); ok {
+		envValInt, err := strconv.ParseInt(envVal, 0, 64)
+		if err != nil {
+			return fmt.Errorf("could not parse %s as int value for flag %s: %s", envVal, f.Name, err)
+		}
+		f.Value = int(envValInt)
+	}
+
+	eachName(f.Name, func(name string) {
+		if f.Destination != nil {
+			set.IntVar(f.Destination, name, f.Value, f.Usage)
+			return
+		}
+		set.Int(name, f.Value, f.Usage)
+	})
+
+	return nil
+}
+
+// Apply populates the flag given the flag set and environment
+// Ignores errors
+func (f Int64Flag) Apply(set *flag.FlagSet) {
+	f.ApplyWithError(set)
 }
 
 func (f StringFlag) IsRequired() bool {
@@ -365,27 +548,54 @@ func (f IntFlag) String() string {
 	return withHints(f.EnvVar, f.Required, fmt.Sprintf("%s \"%v\"\t%v", prefixedNames(f.Name), f.Value, f.Usage))
 }
 
-func (f IntFlag) Apply(set *flag.FlagSet) {
-	if f.EnvVar != "" {
-		for _, envVar := range strings.Split(f.EnvVar, ",") {
-			envVar = strings.TrimSpace(envVar)
-			if envVal := os.Getenv(envVar); envVal != "" {
-				envValInt, err := strconv.ParseInt(envVal, 0, 64)
-				if err == nil {
-					f.Value = int(envValInt)
-					break
-				}
-			}
+// ApplyWithError populates the flag given the flag set and environment
+func (f Int64Flag) ApplyWithError(set *flag.FlagSet) error {
+	if envVal, ok := flagFromFileEnv(f.FilePath, f.EnvVar); ok {
+		envValInt, err := strconv.ParseInt(envVal, 0, 64)
+		if err != nil {
+			return fmt.Errorf("could not parse %s as int value for flag %s: %s", envVal, f.Name, err)
 		}
+
+		f.Value = envValInt
 	}
 
 	eachName(f.Name, func(name string) {
-		set.Int(name, f.Value, f.Usage)
+		if f.Destination != nil {
+			set.Int64Var(f.Destination, name, f.Value, f.Usage)
+			return
+		}
+		set.Int64(name, f.Value, f.Usage)
 	})
+
+	return nil
 }
 
-func (f IntFlag) getName() string {
-	return f.Name
+// Apply populates the flag given the flag set and environment
+// Ignores errors
+func (f UintFlag) Apply(set *flag.FlagSet) {
+	f.ApplyWithError(set)
+}
+
+// ApplyWithError populates the flag given the flag set and environment
+func (f UintFlag) ApplyWithError(set *flag.FlagSet) error {
+	if envVal, ok := flagFromFileEnv(f.FilePath, f.EnvVar); ok {
+		envValInt, err := strconv.ParseUint(envVal, 0, 64)
+		if err != nil {
+			return fmt.Errorf("could not parse %s as uint value for flag %s: %s", envVal, f.Name, err)
+		}
+
+		f.Value = uint(envValInt)
+	}
+
+	eachName(f.Name, func(name string) {
+		if f.Destination != nil {
+			set.UintVar(f.Destination, name, f.Value, f.Usage)
+			return
+		}
+		set.Uint(name, f.Value, f.Usage)
+	})
+
+	return nil
 }
 
 func (f IntFlag) IsRequired() bool {
@@ -404,27 +614,59 @@ func (f DurationFlag) String() string {
 	return withHints(f.EnvVar, f.Required, fmt.Sprintf("%s \"%v\"\t%v", prefixedNames(f.Name), f.Value, f.Usage))
 }
 
-func (f DurationFlag) Apply(set *flag.FlagSet) {
-	if f.EnvVar != "" {
-		for _, envVar := range strings.Split(f.EnvVar, ",") {
-			envVar = strings.TrimSpace(envVar)
-			if envVal := os.Getenv(envVar); envVal != "" {
-				envValDuration, err := time.ParseDuration(envVal)
-				if err == nil {
-					f.Value = envValDuration
-					break
-				}
-			}
+// Apply populates the flag given the flag set and environment
+// Ignores errors
+func (f Uint64Flag) Apply(set *flag.FlagSet) {
+	f.ApplyWithError(set)
+}
+
+// ApplyWithError populates the flag given the flag set and environment
+func (f Uint64Flag) ApplyWithError(set *flag.FlagSet) error {
+	if envVal, ok := flagFromFileEnv(f.FilePath, f.EnvVar); ok {
+		envValInt, err := strconv.ParseUint(envVal, 0, 64)
+		if err != nil {
+			return fmt.Errorf("could not parse %s as uint64 value for flag %s: %s", envVal, f.Name, err)
 		}
+
+		f.Value = uint64(envValInt)
 	}
 
 	eachName(f.Name, func(name string) {
-		set.Duration(name, f.Value, f.Usage)
+		if f.Destination != nil {
+			set.Uint64Var(f.Destination, name, f.Value, f.Usage)
+			return
+		}
+		set.Uint64(name, f.Value, f.Usage)
 	})
+
+	return nil
 }
 
-func (f DurationFlag) getName() string {
-	return f.Name
+// Apply populates the flag given the flag set and environment
+// Ignores errors
+func (f DurationFlag) Apply(set *flag.FlagSet) {
+	f.ApplyWithError(set)
+}
+
+// ApplyWithError populates the flag given the flag set and environment
+func (f DurationFlag) ApplyWithError(set *flag.FlagSet) error {
+	if envVal, ok := flagFromFileEnv(f.FilePath, f.EnvVar); ok {
+		envValDuration, err := time.ParseDuration(envVal)
+		if err != nil {
+			return fmt.Errorf("could not parse %s as duration for flag %s: %s", envVal, f.Name, err)
+		}
+
+		f.Value = envValDuration
+	}
+
+	eachName(f.Name, func(name string) {
+		if f.Destination != nil {
+			set.DurationVar(f.Destination, name, f.Value, f.Usage)
+			return
+		}
+		set.Duration(name, f.Value, f.Usage)
+	})
+	return nil
 }
 
 func (f DurationFlag) IsRequired() bool {
@@ -443,26 +685,43 @@ func (f Float64Flag) String() string {
 	return withHints(f.EnvVar, f.Required, fmt.Sprintf("%s \"%v\"\t%v", prefixedNames(f.Name), f.Value, f.Usage))
 }
 
+// Apply populates the flag given the flag set and environment
+// Ignores errors
 func (f Float64Flag) Apply(set *flag.FlagSet) {
-	if f.EnvVar != "" {
-		for _, envVar := range strings.Split(f.EnvVar, ",") {
-			envVar = strings.TrimSpace(envVar)
-			if envVal := os.Getenv(envVar); envVal != "" {
-				envValFloat, err := strconv.ParseFloat(envVal, 10)
-				if err == nil {
-					f.Value = float64(envValFloat)
-				}
-			}
+	f.ApplyWithError(set)
+}
+
+// ApplyWithError populates the flag given the flag set and environment
+func (f Float64Flag) ApplyWithError(set *flag.FlagSet) error {
+	if envVal, ok := flagFromFileEnv(f.FilePath, f.EnvVar); ok {
+		envValFloat, err := strconv.ParseFloat(envVal, 10)
+		if err != nil {
+			return fmt.Errorf("could not parse %s as float64 value for flag %s: %s", envVal, f.Name, err)
 		}
+
+		f.Value = float64(envValFloat)
 	}
 
 	eachName(f.Name, func(name string) {
+		if f.Destination != nil {
+			set.Float64Var(f.Destination, name, f.Value, f.Usage)
+			return
+		}
 		set.Float64(name, f.Value, f.Usage)
 	})
+
+	return nil
 }
 
-func (f Float64Flag) getName() string {
-	return f.Name
+func visibleFlags(fl []Flag) []Flag {
+	visible := []Flag{}
+	for _, flag := range fl {
+		field := flagValue(flag).FieldByName("Hidden")
+		if !field.IsValid() || !field.Bool() {
+			visible = append(visible, flag)
+		}
+	}
+	return visible
 }
 
 func (f Float64Flag) IsRequired() bool {
@@ -479,22 +738,51 @@ func prefixFor(name string) (prefix string) {
 	return
 }
 
-func prefixedNames(fullName string) (prefixed string) {
+// Returns the placeholder, if any, and the unquoted usage string.
+func unquoteUsage(usage string) (string, string) {
+	for i := 0; i < len(usage); i++ {
+		if usage[i] == '`' {
+			for j := i + 1; j < len(usage); j++ {
+				if usage[j] == '`' {
+					name := usage[i+1 : j]
+					usage = usage[:i] + name + usage[j+1:]
+					return name, usage
+				}
+			}
+			break
+		}
+	}
+	return "", usage
+}
+
+func prefixedNames(fullName, placeholder string) string {
+	var prefixed string
 	parts := strings.Split(fullName, ",")
 	for i, name := range parts {
 		name = strings.Trim(name, " ")
 		prefixed += prefixFor(name) + name
+		if placeholder != "" {
+			prefixed += " " + placeholder
+		}
 		if i < len(parts)-1 {
 			prefixed += ", "
 		}
 	}
-	return
+	return prefixed
 }
 
 func withEnvHint(envVar, str string) string {
 	envText := ""
 	if envVar != "" {
-		envText = fmt.Sprintf(" [$%s]", strings.Join(strings.Split(envVar, ","), ", $"))
+		prefix := "$"
+		suffix := ""
+		sep := ", $"
+		if runtime.GOOS == "windows" {
+			prefix = "%"
+			suffix = "%"
+			sep = "%, %"
+		}
+		envText = " [" + prefix + strings.Join(strings.Split(envVar, ","), sep) + suffix + "]"
 	}
 	return str + envText
 }
@@ -510,3 +798,147 @@ func withRequiredHint(isRequired bool, str string) string {
 func withHints(envVar string, isRequired bool, str string) string {
 	return withRequiredHint(isRequired, withEnvHint(envVar, str))
 }
+
+func withFileHint(filePath, str string) string {
+	fileText := ""
+	if filePath != "" {
+		fileText = fmt.Sprintf(" [%s]", filePath)
+	}
+	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 stringifyFlag(f Flag) string {
+	fv := flagValue(f)
+
+	switch f.(type) {
+	case IntSliceFlag:
+		return FlagFileHinter(
+			fv.FieldByName("FilePath").String(),
+			FlagEnvHinter(
+				fv.FieldByName("EnvVar").String(),
+				stringifyIntSliceFlag(f.(IntSliceFlag)),
+			),
+		)
+	case Int64SliceFlag:
+		return FlagFileHinter(
+			fv.FieldByName("FilePath").String(),
+			FlagEnvHinter(
+				fv.FieldByName("EnvVar").String(),
+				stringifyInt64SliceFlag(f.(Int64SliceFlag)),
+			),
+		)
+	case StringSliceFlag:
+		return FlagFileHinter(
+			fv.FieldByName("FilePath").String(),
+			FlagEnvHinter(
+				fv.FieldByName("EnvVar").String(),
+				stringifyStringSliceFlag(f.(StringSliceFlag)),
+			),
+		)
+	}
+
+	placeholder, usage := unquoteUsage(fv.FieldByName("Usage").String())
+
+	needsPlaceholder := false
+	defaultValueString := ""
+
+	if val := fv.FieldByName("Value"); val.IsValid() {
+		needsPlaceholder = true
+		defaultValueString = fmt.Sprintf(" (default: %v)", val.Interface())
+
+		if val.Kind() == reflect.String && val.String() != "" {
+			defaultValueString = fmt.Sprintf(" (default: %q)", val.String())
+		}
+	}
+
+	if defaultValueString == " (default: )" {
+		defaultValueString = ""
+	}
+
+	if needsPlaceholder && placeholder == "" {
+		placeholder = defaultPlaceholder
+	}
+
+	usageWithDefault := strings.TrimSpace(usage + defaultValueString)
+
+	return FlagFileHinter(
+		fv.FieldByName("FilePath").String(),
+		FlagEnvHinter(
+			fv.FieldByName("EnvVar").String(),
+			FlagNamePrefixer(fv.FieldByName("Name").String(), placeholder)+"\t"+usageWithDefault,
+		),
+	)
+}
+
+func stringifyIntSliceFlag(f IntSliceFlag) string {
+	defaultVals := []string{}
+	if f.Value != nil && len(f.Value.Value()) > 0 {
+		for _, i := range f.Value.Value() {
+			defaultVals = append(defaultVals, strconv.Itoa(i))
+		}
+	}
+
+	return stringifySliceFlag(f.Usage, f.Name, defaultVals)
+}
+
+func stringifyInt64SliceFlag(f Int64SliceFlag) string {
+	defaultVals := []string{}
+	if f.Value != nil && len(f.Value.Value()) > 0 {
+		for _, i := range f.Value.Value() {
+			defaultVals = append(defaultVals, strconv.FormatInt(i, 10))
+		}
+	}
+
+	return stringifySliceFlag(f.Usage, f.Name, defaultVals)
+}
+
+func stringifyStringSliceFlag(f StringSliceFlag) string {
+	defaultVals := []string{}
+	if f.Value != nil && len(f.Value.Value()) > 0 {
+		for _, s := range f.Value.Value() {
+			if len(s) > 0 {
+				defaultVals = append(defaultVals, strconv.Quote(s))
+			}
+		}
+	}
+
+	return stringifySliceFlag(f.Usage, f.Name, defaultVals)
+}
+
+func stringifySliceFlag(usage, name string, defaultVals []string) string {
+	placeholder, usage := unquoteUsage(usage)
+	if placeholder == "" {
+		placeholder = defaultPlaceholder
+	}
+
+	defaultVal := ""
+	if len(defaultVals) > 0 {
+		defaultVal = fmt.Sprintf(" (default: %s)", strings.Join(defaultVals, ", "))
+	}
+
+	usageWithDefault := strings.TrimSpace(usage + defaultVal)
+	return FlagNamePrefixer(name, placeholder) + "\t" + usageWithDefault
+}
+
+func flagFromFileEnv(filePath, envName string) (val string, ok bool) {
+	for _, envVar := range strings.Split(envName, ",") {
+		envVar = strings.TrimSpace(envVar)
+		if envVal, ok := syscall.Getenv(envVar); ok {
+			return envVal, true
+		}
+	}
+	for _, fileVar := range strings.Split(filePath, ",") {
+		if data, err := ioutil.ReadFile(fileVar); err == nil {
+			return string(data), true
+		}
+	}
+	return "", false
+}