Enable to customize completion commands

command.go

@@ -56,6 +56,8 @@ type Command struct {
 	ShellCompletionCommandName string `json:"-"`
 	// The function to call when checking for shell command completions
 	ShellComplete ShellCompleteFunc `json:"-"`
+	// The function to configure a shell completion command
+	ConfigureShellCompletionCommand ConfigureShellCompletionCommand `json:"-"`
 	// An action to execute before any subcommands are run, but after the context is ready
 	// If a non-nil error is returned, no subcommands are run
 	Before BeforeFunc `json:"-"`

command_setup.go

@@ -88,7 +88,7 @@ func (cmd *Command) setupDefaults(osArgs []string) {
 		cmd.SuggestCommandFunc = suggestCommand
 	}
 
-	if isRoot && cmd.EnableShellCompletion {
+	if isRoot && cmd.EnableShellCompletion || cmd.ConfigureShellCompletionCommand != nil {
 		completionCommand := buildCompletionCommand(cmd.Name)
 
 		if cmd.ShellCompletionCommandName != "" {
@@ -102,6 +102,9 @@ func (cmd *Command) setupDefaults(osArgs []string) {
 
 		tracef("appending completionCommand (cmd=%[1]q)", cmd.Name)
 		cmd.appendCommand(completionCommand)
+		if cmd.ConfigureShellCompletionCommand != nil {
+			cmd.ConfigureShellCompletionCommand(completionCommand)
+		}
 	}
 
 	tracef("setting command categories (cmd=%[1]q)", cmd.Name)

completion.go

@@ -5,6 +5,7 @@ import (
 	"embed"
 	"fmt"
 	"sort"
+	"strings"
 )
 
 const (
@@ -39,10 +40,28 @@ var (
 	}
 )
 
+const completionDescription = `Output shell completion script for bash, zsh, fish, or Powershell.
+Source the output to enable completion.
+
+# .bashrc
+source <($COMMAND completion bash)
+
+# .zshrc
+source <($COMMAND completion zsh)
+
+# fish
+$COMMAND completion fish > ~/.config/fish/completions/$COMMAND.fish
+
+# Powershell
+Output the script to path/to/autocomplete/$COMMAND.ps1 an run it.
+`
+
 func buildCompletionCommand(appName string) *Command {
 	return &Command{
-		Name:   completionCommandName,
-		Hidden: true,
+		Name:        completionCommandName,
+		Hidden:      true,
+		Usage:       "Output shell completion script for bash, zsh, fish, or Powershell",
+		Description: strings.ReplaceAll(completionDescription, "$COMMAND", appName),
 		Action: func(ctx context.Context, cmd *Command) error {
 			return printShellCompletion(ctx, cmd, appName)
 		},

docs/v3/examples/completions/shell-completions.md

@@ -233,6 +233,50 @@ func main() {
 ```
 ![](../../images/custom-bash-autocomplete.gif)
 
+#### Customize a completion command
+
+By default, a completion command is hidden, meaning the command isn't included in the help message.
+You can customize it by setting root Command's `ConfigureShellCompletionCommand`.
+
+```go
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/urfave/cli/v3"
+)
+
+func main() {
+	cmd := &cli.Command{
+		Name: "greet",
+		// EnableShellCompletion is unnecessary
+		ConfigureShellCompletionCommand: func(cmd *cli.Command) { // cmd is a completion command
+			cmd.Hidden = false // Make a completion command public
+			cmd.Usage = "..." // Customize Usage
+			cmd.Description = "..." // Customize Description
+		},
+		Commands: []*cli.Command{
+			{
+				Name:  "hello",
+				Usage: "Say hello",
+				Action: func(ctx context.Context, cmd *cli.Command) error {
+					fmt.Println("Hello")
+					return nil
+				},
+			},
+		},
+	}
+
+	if err := cmd.Run(context.Background(), os.Args); err != nil {
+		log.Fatal(err)
+	}
+}
+```
+
 #### Customization
 
 The default shell completion flag (`--generate-shell-completion`) is defined as

funcs.go

@@ -20,6 +20,9 @@ type ActionFunc func(context.Context, *Command) error
 // CommandNotFoundFunc is executed if the proper command cannot be found
 type CommandNotFoundFunc func(context.Context, *Command, string)
 
+// ConfigureShellCompletionCommand is a function to configure a shell completion command
+type ConfigureShellCompletionCommand func(*Command)
+
 // OnUsageErrorFunc is executed if a usage error occurs. This is useful for displaying
 // customized usage error messages.  This function is able to replace the
 // original error messages.  If this function is not set, the "Incorrect usage"

godoc-current.txt

@@ -433,6 +433,8 @@ type Command struct {
 	ShellCompletionCommandName string `json:"-"`
 	// The function to call when checking for shell command completions
 	ShellComplete ShellCompleteFunc `json:"-"`
+	// The function to configure a shell completion command
+	ConfigureShellCompletionCommand ConfigureShellCompletionCommand `json:"-"`
 	// An action to execute before any subcommands are run, but after the context is ready
 	// If a non-nil error is returned, no subcommands are run
 	Before BeforeFunc `json:"-"`
@@ -751,6 +753,10 @@ type CommandCategory interface {
 type CommandNotFoundFunc func(context.Context, *Command, string)
     CommandNotFoundFunc is executed if the proper command cannot be found
 
+type ConfigureShellCompletionCommand func(*Command)
+    ConfigureShellCompletionCommand is a function to configure a shell
+    completion command
+
 type Countable interface {
 	Count() int
 }

testdata/godoc-v3.x.txt

@@ -433,6 +433,8 @@ type Command struct {
 	ShellCompletionCommandName string `json:"-"`
 	// The function to call when checking for shell command completions
 	ShellComplete ShellCompleteFunc `json:"-"`
+	// The function to configure a shell completion command
+	ConfigureShellCompletionCommand ConfigureShellCompletionCommand `json:"-"`
 	// An action to execute before any subcommands are run, but after the context is ready
 	// If a non-nil error is returned, no subcommands are run
 	Before BeforeFunc `json:"-"`
@@ -751,6 +753,10 @@ type CommandCategory interface {
 type CommandNotFoundFunc func(context.Context, *Command, string)
     CommandNotFoundFunc is executed if the proper command cannot be found
 
+type ConfigureShellCompletionCommand func(*Command)
+    ConfigureShellCompletionCommand is a function to configure a shell
+    completion command
+
 type Countable interface {
 	Count() int
 }