Improve the command for printing completion scripts

command.go

@@ -257,7 +257,7 @@ func (cmd *Command) setupDefaults(osArgs []string) {
 	}
 
 	if cmd.EnableShellCompletion || cmd.Root().shellCompletion {
-		completionCommand := buildCompletionCommand()
+		completionCommand := buildCompletionCommand(osArgs[0])
 
 		if cmd.ShellCompletionCommandName != "" {
 			tracef(

completion.go

@@ -2,49 +2,45 @@ package cli
 
 import (
 	"context"
-	"embed"
 	"fmt"
 	"sort"
 )
 
 const (
-	completionCommandName = "generate-completion"
-	completionFlagName    = "generate-shell-completion"
-	completionFlag        = "--" + completionFlagName
-)
-
-var (
-	//go:embed autocomplete
-	autoCompleteFS embed.FS
+	completionCommandName = "completion"
 
-	shellCompletions = map[string]renderCompletion{
-		"bash": getCompletion("autocomplete/bash_autocomplete"),
-		"ps":   getCompletion("autocomplete/powershell_autocomplete.ps1"),
-		"zsh":  getCompletion("autocomplete/zsh_autocomplete"),
-		"fish": func(c *Command) (string, error) {
-			return c.ToFishCompletion()
-		},
-	}
+	// This flag is supposed to only be used by the completion script itself to generate completions on the fly.
+	completionFlag = "--generate-shell-completion"
 )
 
-type renderCompletion func(*Command) (string, error)
-
-func getCompletion(s string) renderCompletion {
-	return func(c *Command) (string, error) {
-		b, err := autoCompleteFS.ReadFile(s)
-		return string(b), err
-	}
+var shellCompletions = map[string]renderCompletionFunc{
+	"bash": func(cmd *Command, appName string) (string, error) {
+		return genBashCompletion(appName), nil
+	},
+	"zsh": func(cmd *Command, appName string) (string, error) {
+		return genZshCompletion(appName), nil
+	},
+	"fish": func(c *Command, appName string) (string, error) {
+		return c.ToFishCompletion()
+	},
+	"pwsh": func(cmd *Command, appName string) (string, error) {
+		return genPwshCompletion(), nil
+	},
 }
 
-func buildCompletionCommand() *Command {
+type renderCompletionFunc func(cmd *Command, appName string) (string, error)
+
+func buildCompletionCommand(appName string) *Command {
 	return &Command{
 		Name:   completionCommandName,
 		Hidden: true,
-		Action: completionCommandAction,
+		Action: func(ctx context.Context, cmd *Command) error {
+			return printShellCompletion(ctx, cmd, appName)
+		},
 	}
 }
 
-func completionCommandAction(ctx context.Context, cmd *Command) error {
+func printShellCompletion(_ context.Context, cmd *Command, appName string) error {
 	var shells []string
 	for k := range shellCompletions {
 		shells = append(shells, k)
@@ -57,14 +53,103 @@ func completionCommandAction(ctx context.Context, cmd *Command) error {
 	}
 	s := cmd.Args().First()
 
-	if rc, ok := shellCompletions[s]; !ok {
+	renderCompletion, ok := shellCompletions[s]
+	if !ok {
 		return Exit(fmt.Sprintf("unknown shell %s, available shells are %+v", s, shells), 1)
-	} else if c, err := rc(cmd); err != nil {
+	}
+
+	completionScript, err := renderCompletion(cmd, appName)
+	if err != nil {
+		return Exit(err, 1)
+	}
+
+	_, err = cmd.Writer.Write([]byte(completionScript))
+	if err != nil {
 		return Exit(err, 1)
-	} else {
-		if _, err = cmd.Writer.Write([]byte(c)); err != nil {
-			return Exit(err, 1)
-		}
 	}
+
 	return nil
 }
+
+func genBashCompletion(appName string) string {
+	return fmt.Sprintf(`#!/usr/env/bin bash
+
+# This is a shell completion script auto-generated by https://github.com/urfave/cli for bash.
+
+# Macs have bash3 for which the bash-completion package doesn't include
+# _init_completion. This is a minimal version of that function.
+__%[1]s_init_completion() {
+  COMPREPLY=()
+  _get_comp_words_by_ref "$@" cur prev words cword
+}
+
+__%[1]s_bash_autocomplete() {
+  if [[ "${COMP_WORDS[0]}" != "source" ]]; then
+    local cur opts base words
+    COMPREPLY=()
+    cur="${COMP_WORDS[COMP_CWORD]}"
+    if declare -F _init_completion >/dev/null 2>&1; then
+      _init_completion -n "=:" || return
+    else
+      __%[1]s_init_completion -n "=:" || return
+    fi
+    words=("${words[@]:0:$cword}")
+    if [[ "$cur" == "-"* ]]; then
+      requestComp="${words[*]} ${cur} --generate-shell-completion"
+    else
+      requestComp="${words[*]} --generate-shell-completion"
+    fi
+    opts=$(eval "${requestComp}" 2>/dev/null)
+    COMPREPLY=($(compgen -W "${opts}" -- ${cur}))
+    return 0
+  fi
+}
+
+complete -o bashdefault -o default -o nospace -F __%[1]s_bash_autocomplete %[1]s
+`, appName)
+}
+
+func genZshCompletion(appName string) string {
+	return fmt.Sprintf(`#compdef %[1]s
+compdef _%[1]s %[1]s
+
+# This is a shell completion script auto-generated by https://github.com/urfave/cli for zsh.
+
+_%[1]s() {
+	local -a opts # Declare a local array
+	local current
+	current=${words[-1]} # -1 means "the last element"
+	if [[ "$current" == "-"* ]]; then
+		# Current word starts with a hyphen, so complete flags/options
+		opts=("${(@f)$(${words[@]:0:#words[@]-1} ${current} --generate-shell-completion)}")
+	else
+		# Current word does not start with a hyphen, so complete subcommands
+		opts=("${(@f)$(${words[@]:0:#words[@]-1} --generate-shell-completion)}")
+	fi
+
+	if [[ "${opts[1]}" != "" ]]; then
+		_describe 'values' opts
+	else
+		_files
+	fi
+}
+
+# Don't run the completion function when being source-ed or eval-ed.
+# See https://github.com/urfave/cli/issues/1874 for discussion.
+if [ "$funcstack[1]" = "_%[1]s" ]; then
+	_%[1]s
+fi
+`, appName)
+}
+
+func genPwshCompletion() string {
+	return `$fn = $($MyInvocation.MyCommand.Name)
+$name = $fn -replace "(.*)\.ps1$", '$1'
+Register-ArgumentCompleter -Native -CommandName $name -ScriptBlock {
+     param($commandName, $wordToComplete, $cursorPosition)
+     $other = "$wordToComplete --generate-shell-completion"
+         Invoke-Expression $other | ForEach-Object {
+            [System.Management.Automation.CompletionResult]::new($_, $_, 'ParameterValue', $_)
+         }
+ }`
+}

completion_test.go

@@ -200,7 +200,7 @@ func TestCompletionInvalidShell(t *testing.T) {
 	assert.ErrorContains(t, err, "unknown shell junky-sheell")
 
 	enableError := true
-	shellCompletions[unknownShellName] = func(c *Command) (string, error) {
+	shellCompletions[unknownShellName] = func(c *Command, appName string) (string, error) {
 		if enableError {
 			return "", fmt.Errorf("cant do completion")
 		}

examples/simpletask/main.go

@@ -0,0 +1,70 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/urfave/cli/v3"
+)
+
+func main() {
+	app := &cli.Command{
+		Name:                  "simpletask",
+		Usage:                 "a dead simple task manager",
+		EnableShellCompletion: true,
+		Action: func(ctx context.Context, command *cli.Command) error {
+			fmt.Println("decide what to do!")
+			return nil
+		},
+		Commands: []*cli.Command{
+			{
+				Name:    "add",
+				Aliases: []string{"a"},
+				Usage:   "add a task to the list",
+				Action: func(ctx context.Context, cmd *cli.Command) error {
+					fmt.Println("added task: ", cmd.Args().First())
+					return nil
+				},
+			},
+			{
+				Name:    "complete",
+				Aliases: []string{"c"},
+				Usage:   "complete a task on the list",
+				Action: func(ctx context.Context, cmd *cli.Command) error {
+					fmt.Println("completed task: ", cmd.Args().First())
+					return nil
+				},
+			},
+			{
+				Name:    "template",
+				Aliases: []string{"t"},
+				Usage:   "options for task templates",
+				Commands: []*cli.Command{
+					{
+						Name:  "add",
+						Usage: "add a new template",
+						Action: func(ctx context.Context, cmd *cli.Command) error {
+							fmt.Println("new task template: ", cmd.Args().First())
+							return nil
+						},
+					},
+					{
+						Name:  "remove",
+						Usage: "remove an existing template",
+						Action: func(ctx context.Context, cmd *cli.Command) error {
+							fmt.Println("removed task template: ", cmd.Args().First())
+							return nil
+						},
+					},
+				},
+			},
+		},
+	}
+
+	err := app.Run(context.Background(), os.Args)
+	if err != nil {
+		log.Fatal(err)
+	}
+}

help.go

@@ -190,8 +190,9 @@ func cliArgContains(flagName string, args []string) bool {
 }
 
 func printFlagSuggestions(lastArg string, flags []Flag, writer io.Writer) {
-	cur := strings.TrimPrefix(lastArg, "-")
-	cur = strings.TrimPrefix(cur, "-")
+	// Trim the prefix twice to handle both "-short" and "--long" flags.
+	currentArg := strings.TrimPrefix(lastArg, "-")
+	currentArg = strings.TrimPrefix(currentArg, "-")
 	for _, flag := range flags {
 		if bflag, ok := flag.(*BoolFlag); ok && bflag.Hidden {
 			continue
@@ -214,7 +215,7 @@ func printFlagSuggestions(lastArg string, flags []Flag, writer io.Writer) {
 			continue
 		}
 		// match if last argument matches this flag and it is not repeated
-		if strings.HasPrefix(name, cur) && cur != name && !cliArgContains(name, os.Args) {
+		if strings.HasPrefix(name, currentArg) && currentArg != name && !cliArgContains(name, os.Args) {
 			flagCompletion := fmt.Sprintf("%s%s", strings.Repeat("-", count), name)
 			if usage != "" && strings.HasSuffix(os.Getenv("SHELL"), "zsh") {
 				flagCompletion = fmt.Sprintf("%s:%s", flagCompletion, usage)