Implement required flags

app.go

@@ -87,14 +87,25 @@ func (a *App) Run(arguments []string) error {
 	set.SetOutput(ioutil.Discard)
 	err := set.Parse(arguments[1:])
 	nerr := normalizeFlags(a.Flags, set)
+	cerr := checkRequiredFlags(a.Flags, set)
+
+	context := NewContext(a, set, set)
+
 	if nerr != nil {
 		fmt.Println(nerr)
-		context := NewContext(a, set, set)
+		fmt.Println("")
 		ShowAppHelp(context)
 		fmt.Println("")
 		return nerr
 	}
-	context := NewContext(a, set, set)
+
+	if cerr != nil {
+		fmt.Println(cerr)
+		fmt.Println("")
+		ShowAppHelp(context)
+		fmt.Println("")
+		return cerr
+	}
 
 	if err != nil {
 		fmt.Printf("Incorrect Usage.\n\n")
@@ -164,10 +175,13 @@ func (a *App) RunAsSubcommand(ctx *Context) error {
 	set.SetOutput(ioutil.Discard)
 	err := set.Parse(ctx.Args().Tail())
 	nerr := normalizeFlags(a.Flags, set)
+	cerr := checkRequiredFlags(a.Flags, set)
+
 	context := NewContext(a, set, ctx.globalSet)
 
 	if nerr != nil {
 		fmt.Println(nerr)
+		fmt.Println("")
 		if len(a.Commands) > 0 {
 			ShowSubcommandHelp(context)
 		} else {
@@ -177,6 +191,20 @@ func (a *App) RunAsSubcommand(ctx *Context) error {
 		return nerr
 	}
 
+	if cerr != nil {
+		fmt.Println(cerr)
+		fmt.Println("")
+		if len(a.Commands) > 0 {
+			ShowSubcommandHelp(context)
+			fmt.Println("subcommands")
+		} else {
+			ShowCommandHelp(ctx, context.Args().First())
+			fmt.Println("commands")
+		}
+		fmt.Println("")
+		return cerr
+	}
+
 	if err != nil {
 		fmt.Printf("Incorrect Usage.\n\n")
 		ShowSubcommandHelp(context)

command.go

@@ -88,6 +88,16 @@ func (c Command) Run(ctx *Context) error {
 		fmt.Println("")
 		return nerr
 	}
+
+	cerr := checkRequiredFlags(c.Flags, set)
+	if cerr != nil {
+		fmt.Println(cerr)
+		fmt.Println("")
+		ShowCommandHelp(ctx, c.Name)
+		fmt.Println("")
+		return cerr
+	}
+
 	context := NewContext(ctx.App, set, ctx.globalSet)
 
 	if checkCommandCompletions(context, c.Name) {

context.go

@@ -3,6 +3,7 @@ package cli
 import (
 	"errors"
 	"flag"
+	"fmt"
 	"strconv"
 	"strings"
 	"time"
@@ -337,3 +338,20 @@ func normalizeFlags(flags []Flag, set *flag.FlagSet) error {
 	}
 	return nil
 }
+
+func checkRequiredFlags(flags []Flag, set *flag.FlagSet) error {
+	visited := make(map[string]bool)
+	set.Visit(func(f *flag.Flag) {
+		visited[f.Name] = true
+	})
+
+	for _, f := range flags {
+		if f.IsRequired() {
+			key := strings.Split(f.getName(), ",")[0]
+			if !visited[key] {
+				return fmt.Errorf("Required flag %s not set", f.getName())
+			}
+		}
+	}
+	return nil
+}

flag.go

@@ -34,6 +34,7 @@ type Flag interface {
 	// Apply Flag settings to the given flag set
 	Apply(*flag.FlagSet)
 	getName() string
+	IsRequired() bool
 }
 
 func flagSet(name string, flags []Flag) *flag.FlagSet {
@@ -61,10 +62,11 @@ type Generic interface {
 
 // GenericFlag is the flag type for types implementing Generic
 type GenericFlag struct {
-	Name   string
+	Name     string
-	Value  Generic
+	Value    Generic
-	Usage  string
+	Usage    string
-	EnvVar string
+	EnvVar   string
+	Required bool
 }
 
 func (f GenericFlag) String() string {
@@ -88,6 +90,10 @@ func (f GenericFlag) getName() string {
 	return f.Name
 }
 
+func (f GenericFlag) IsRequired() bool {
+	return f.Required
+}
+
 type StringSlice []string
 
 func (f *StringSlice) Set(value string) error {
@@ -104,10 +110,11 @@ func (f *StringSlice) Value() []string {
 }
 
 type StringSliceFlag struct {
-	Name   string
+	Name     string
-	Value  *StringSlice
+	Value    *StringSlice
-	Usage  string
+	Usage    string
-	EnvVar string
+	EnvVar   string
+	Required bool
 }
 
 func (f StringSliceFlag) String() string {
@@ -136,6 +143,10 @@ func (f StringSliceFlag) getName() string {
 	return f.Name
 }
 
+func (f StringSliceFlag) IsRequired() bool {
+	return f.Required
+}
+
 type IntSlice []int
 
 func (f *IntSlice) Set(value string) error {
@@ -158,10 +169,11 @@ func (f *IntSlice) Value() []int {
 }
 
 type IntSliceFlag struct {
-	Name   string
+	Name     string
-	Value  *IntSlice
+	Value    *IntSlice
-	Usage  string
+	Usage    string
-	EnvVar string
+	EnvVar   string
+	Required bool
 }
 
 func (f IntSliceFlag) String() string {
@@ -193,10 +205,15 @@ func (f IntSliceFlag) getName() string {
 	return f.Name
 }
 
+func (f IntSliceFlag) IsRequired() bool {
+	return f.Required
+}
+
 type BoolFlag struct {
-	Name   string
+	Name     string
-	Usage  string
+	Usage    string
-	EnvVar string
+	EnvVar   string
+	Required bool
 }
 
 func (f BoolFlag) String() string {
@@ -223,10 +240,15 @@ func (f BoolFlag) getName() string {
 	return f.Name
 }
 
+func (f BoolFlag) IsRequired() bool {
+	return f.Required
+}
+
 type BoolTFlag struct {
-	Name   string
+	Name     string
-	Usage  string
+	Usage    string
-	EnvVar string
+	EnvVar   string
+	Required bool
 }
 
 func (f BoolTFlag) String() string {
@@ -253,11 +275,16 @@ func (f BoolTFlag) getName() string {
 	return f.Name
 }
 
+func (f BoolTFlag) IsRequired() bool {
+	return f.Required
+}
+
 type StringFlag struct {
-	Name   string
+	Name     string
-	Value  string
+	Value    string
-	Usage  string
+	Usage    string
-	EnvVar string
+	EnvVar   string
+	Required bool
 }
 
 func (f StringFlag) String() string {
@@ -289,11 +316,16 @@ func (f StringFlag) getName() string {
 	return f.Name
 }
 
+func (f StringFlag) IsRequired() bool {
+	return f.Required
+}
+
 type IntFlag struct {
-	Name   string
+	Name     string
-	Value  int
+	Value    int
-	Usage  string
+	Usage    string
-	EnvVar string
+	EnvVar   string
+	Required bool
 }
 
 func (f IntFlag) String() string {
@@ -319,11 +351,16 @@ func (f IntFlag) getName() string {
 	return f.Name
 }
 
+func (f IntFlag) IsRequired() bool {
+	return f.Required
+}
+
 type DurationFlag struct {
-	Name   string
+	Name     string
-	Value  time.Duration
+	Value    time.Duration
-	Usage  string
+	Usage    string
-	EnvVar string
+	EnvVar   string
+	Required bool
 }
 
 func (f DurationFlag) String() string {
@@ -349,11 +386,16 @@ func (f DurationFlag) getName() string {
 	return f.Name
 }
 
+func (f DurationFlag) IsRequired() bool {
+	return f.Required
+}
+
 type Float64Flag struct {
-	Name   string
+	Name     string
-	Value  float64
+	Value    float64
-	Usage  string
+	Usage    string
-	EnvVar string
+	EnvVar   string
+	Required bool
 }
 
 func (f Float64Flag) String() string {
@@ -379,6 +421,10 @@ func (f Float64Flag) getName() string {
 	return f.Name
 }
 
+func (f Float64Flag) IsRequired() bool {
+	return f.Required
+}
+
 func prefixFor(name string) (prefix string) {
 	if len(name) == 1 {
 		prefix = "-"