feat: flag action

app.go

@@ -340,6 +340,10 @@ func (a *App) RunContext(ctx context.Context, arguments []string) (err error) {
 		}
 	}
 
+	if err = runFlagActions(cCtx, a.Flags); err != nil {
+		return err
+	}
+
 	var c *Command
 	args := cCtx.Args()
 	if args.Present() {
@@ -521,6 +525,10 @@ func (a *App) RunAsSubcommand(ctx *Context) (err error) {
 		}
 	}
 
+	if err = runFlagActions(cCtx, a.Flags); err != nil {
+		return err
+	}
+
 	args := cCtx.Args()
 	if args.Present() {
 		name := args.First()
@@ -644,6 +652,24 @@ func (a *App) argsWithDefaultCommand(oldArgs Args) Args {
 	return oldArgs
 }
 
+func runFlagActions(c *Context, fs []Flag) error {
+	for _, f := range fs {
+		isSet := false
+		for _, name := range f.Names() {
+			if c.IsSet(name) {
+				isSet = true
+				break
+			}
+		}
+		if isSet {
+			if err := f.RunAction(c); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
 // Author represents someone who has contributed to a cli project.
 type Author struct {
 	Name  string // The Authors name

app_test.go

@@ -2357,6 +2357,10 @@ func (c *customBoolFlag) Apply(set *flag.FlagSet) error {
 	return nil
 }
 
+func (c *customBoolFlag) RunAction(*Context) error {
+	return nil
+}
+
 func (c *customBoolFlag) IsSet() bool {
 	return false
 }
@@ -2596,3 +2600,66 @@ func TestSetupInitializesOnlyNilWriters(t *testing.T) {
 		t.Errorf("expected a.Writer to be os.Stdout")
 	}
 }
+
+func TestFlagAction(t *testing.T) {
+	r := []string{}
+	actionFunc := func(c *Context, s string) error {
+		r = append(r, s)
+		return nil
+	}
+
+	app := &App{
+		Name:   "command",
+		Writer: io.Discard,
+		Flags:  []Flag{&StringFlag{Name: "flag", Action: actionFunc}},
+		Commands: []*Command{
+			{
+				Name:  "command1",
+				Flags: []Flag{&StringFlag{Name: "flag1", Aliases: []string{"f1"}, Action: actionFunc}},
+				Subcommands: []*Command{
+					{
+						Name:  "command2",
+						Flags: []Flag{&StringFlag{Name: "flag2", Action: actionFunc}},
+					},
+				},
+			},
+		},
+	}
+
+	tests := []struct {
+		args []string
+		exp  []string
+	}{
+		{
+			args: []string{"command", "--flag=f"},
+			exp:  []string{"f"},
+		},
+		{
+			args: []string{"command", "command1", "-f1=f1", "command2"},
+			exp:  []string{"f1"},
+		},
+		{
+			args: []string{"command", "command1", "-f1=f1", "command2", "--flag2=f2"},
+			exp:  []string{"f1", "f2"},
+		},
+		{
+			args: []string{"command", "--flag=f", "command1", "-flag1=f1"},
+			exp:  []string{"f", "f1"},
+		},
+		{
+			args: []string{"command", "--flag=f", "command1", "-f1=f1"},
+			exp:  []string{"f", "f1"},
+		},
+		{
+			args: []string{"command", "--flag=f", "command1", "-f1=f1", "command2", "--flag2=f2"},
+			exp:  []string{"f", "f1", "f2"},
+		},
+	}
+
+	for _, test := range tests {
+		r = []string{}
+		err := app.Run(test.args)
+		expect(t, err, nil)
+		expect(t, r, test.exp)
+	}
+}

command.go

@@ -165,6 +165,10 @@ func (c *Command) Run(ctx *Context) (err error) {
 		}
 	}
 
+	if err = runFlagActions(cCtx, c.Flags); err != nil {
+		return err
+	}
+
 	if c.Action == nil {
 		c.Action = helpSubcommand.Action
 	}

flag.go

@@ -122,6 +122,8 @@ type Flag interface {
 	// GetValue returns the flags value as string representation and an empty
 	// string if the flag takes no value at all.
 	GetValue() string
+
+	RunAction(*Context) error
 }
 
 // Countable is an interface to enable detection of flag values which support

flag_bool.go

@@ -72,6 +72,15 @@ func (f *BoolFlag) GetDefaultText() string {
 	return fmt.Sprintf("%v", f.Value)
 }
 
+// RunAction executes flag action if set
+func (f *BoolFlag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.Bool(f.Name))
+	}
+
+	return nil
+}
+
 // Apply populates the flag given the flag set and environment
 func (f *BoolFlag) Apply(set *flag.FlagSet) error {
 	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {

flag_duration.go

@@ -42,6 +42,15 @@ func (f *DurationFlag) Get(ctx *Context) time.Duration {
 	return ctx.Duration(f.Name)
 }
 
+// RunAction executes flag action if set
+func (f *DurationFlag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.Duration(f.Name))
+	}
+
+	return nil
+}
+
 // Duration looks up the value of a local DurationFlag, returns
 // 0 if not found
 func (cCtx *Context) Duration(name string) time.Duration {

flag_float64.go

@@ -42,6 +42,15 @@ func (f *Float64Flag) Get(ctx *Context) float64 {
 	return ctx.Float64(f.Name)
 }
 
+// RunAction executes flag action if set
+func (f *Float64Flag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.Float64(f.Name))
+	}
+
+	return nil
+}
+
 // Float64 looks up the value of a local Float64Flag, returns
 // 0 if not found
 func (cCtx *Context) Float64(name string) float64 {

flag_float64_slice.go

@@ -153,6 +153,15 @@ func (f *Float64SliceFlag) stringify() string {
 	return stringifySliceFlag(f.Usage, f.Names(), defaultVals)
 }
 
+// RunAction executes flag action if set
+func (f *Float64SliceFlag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.Float64Slice(f.Name))
+	}
+
+	return nil
+}
+
 // Float64Slice looks up the value of a local Float64SliceFlag, returns
 // nil if not found
 func (cCtx *Context) Float64Slice(name string) []float64 {

flag_generic.go

@@ -45,6 +45,15 @@ func (f *GenericFlag) Get(ctx *Context) interface{} {
 	return ctx.Generic(f.Name)
 }
 
+// RunAction executes flag action if set
+func (f *GenericFlag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.Generic(f.Name))
+	}
+
+	return nil
+}
+
 // Generic looks up the value of a local GenericFlag, returns
 // nil if not found
 func (cCtx *Context) Generic(name string) interface{} {

flag_int.go

@@ -43,6 +43,15 @@ func (f *IntFlag) Get(ctx *Context) int {
 	return ctx.Int(f.Name)
 }
 
+// RunAction executes flag action if set
+func (f *IntFlag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.Int(f.Name))
+	}
+
+	return nil
+}
+
 // Int looks up the value of a local IntFlag, returns
 // 0 if not found
 func (cCtx *Context) Int(name string) int {

flag_int64.go

@@ -42,6 +42,15 @@ func (f *Int64Flag) Get(ctx *Context) int64 {
 	return ctx.Int64(f.Name)
 }
 
+// RunAction executes flag action if set
+func (f *Int64Flag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.Int64(f.Name))
+	}
+
+	return nil
+}
+
 // Int64 looks up the value of a local Int64Flag, returns
 // 0 if not found
 func (cCtx *Context) Int64(name string) int64 {

flag_int64_slice.go

@@ -151,6 +151,15 @@ func (f *Int64SliceFlag) stringify() string {
 	return stringifySliceFlag(f.Usage, f.Names(), defaultVals)
 }
 
+// RunAction executes flag action if set
+func (f *Int64SliceFlag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.Int64Slice(f.Name))
+	}
+
+	return nil
+}
+
 // Int64Slice looks up the value of a local Int64SliceFlag, returns
 // nil if not found
 func (cCtx *Context) Int64Slice(name string) []int64 {

flag_int_slice.go

@@ -162,6 +162,15 @@ func (f *IntSliceFlag) stringify() string {
 	return stringifySliceFlag(f.Usage, f.Names(), defaultVals)
 }
 
+// RunAction executes flag action if set
+func (f *IntSliceFlag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.IntSlice(f.Name))
+	}
+
+	return nil
+}
+
 // IntSlice looks up the value of a local IntSliceFlag, returns
 // nil if not found
 func (cCtx *Context) IntSlice(name string) []int {

flag_path.go

@@ -47,6 +47,15 @@ func (f *PathFlag) Get(ctx *Context) string {
 	return ctx.Path(f.Name)
 }
 
+// RunAction executes flag action if set
+func (f *PathFlag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.Path(f.Name))
+	}
+
+	return nil
+}
+
 // Path looks up the value of a local PathFlag, returns
 // "" if not found
 func (cCtx *Context) Path(name string) string {

flag_string.go

@@ -45,6 +45,15 @@ func (f *StringFlag) Get(ctx *Context) string {
 	return ctx.String(f.Name)
 }
 
+// RunAction executes flag action if set
+func (f *StringFlag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.String(f.Name))
+	}
+
+	return nil
+}
+
 // String looks up the value of a local StringFlag, returns
 // "" if not found
 func (cCtx *Context) String(name string) string {

flag_string_slice.go

@@ -143,6 +143,15 @@ func (f *StringSliceFlag) stringify() string {
 	return stringifySliceFlag(f.Usage, f.Names(), defaultVals)
 }
 
+// RunAction executes flag action if set
+func (f *StringSliceFlag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.StringSlice(f.Name))
+	}
+
+	return nil
+}
+
 // StringSlice looks up the value of a local StringSliceFlag, returns
 // nil if not found
 func (cCtx *Context) StringSlice(name string) []string {

flag_timestamp.go

@@ -120,6 +120,15 @@ func (f *TimestampFlag) Get(ctx *Context) *time.Time {
 	return ctx.Timestamp(f.Name)
 }
 
+// RunAction executes flag action if set
+func (f *TimestampFlag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.Timestamp(f.Name))
+	}
+
+	return nil
+}
+
 // Timestamp gets the timestamp from a flag name
 func (cCtx *Context) Timestamp(name string) *time.Time {
 	if fs := cCtx.lookupFlagSet(name); fs != nil {

flag_uint.go

@@ -42,6 +42,15 @@ func (f *UintFlag) Get(ctx *Context) uint {
 	return ctx.Uint(f.Name)
 }
 
+// RunAction executes flag action if set
+func (f *UintFlag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.Uint(f.Name))
+	}
+
+	return nil
+}
+
 // Uint looks up the value of a local UintFlag, returns
 // 0 if not found
 func (cCtx *Context) Uint(name string) uint {

flag_uint64.go

@@ -42,6 +42,15 @@ func (f *Uint64Flag) Get(ctx *Context) uint64 {
 	return ctx.Uint64(f.Name)
 }
 
+// RunAction executes flag action if set
+func (f *Uint64Flag) RunAction(c *Context) error {
+	if f.Action != nil {
+		return f.Action(c, c.Uint64(f.Name))
+	}
+
+	return nil
+}
+
 // Uint64 looks up the value of a local Uint64Flag, returns
 // 0 if not found
 func (cCtx *Context) Uint64(name string) uint64 {