Add completion for help command (#1136)

* Don't exclude 'help' from bash completions

Fixes #1000.

* Provide completion for the help command

1- Show 'help' as a possible completion
2- Provide completions for the help command itself

Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>

Co-authored-by: Zaven Muradyan <voithos@google.com>

bash_completions.go

@@ -389,7 +389,7 @@ fi
 func writeCommands(buf *bytes.Buffer, cmd *Command) {
 	buf.WriteString("    commands=()\n")
 	for _, c := range cmd.Commands() {
-		if !c.IsAvailableCommand() || c == cmd.helpCommand {
+		if !c.IsAvailableCommand() && c != cmd.helpCommand {
 			continue
 		}
 		buf.WriteString(fmt.Sprintf("    commands+=(%q)\n", c.Name()))
@@ -582,7 +582,7 @@ func writeArgAliases(buf *bytes.Buffer, cmd *Command) {
 
 func gen(buf *bytes.Buffer, cmd *Command) {
 	for _, c := range cmd.Commands() {
-		if !c.IsAvailableCommand() || c == cmd.helpCommand {
+		if !c.IsAvailableCommand() && c != cmd.helpCommand {
 			continue
 		}
 		gen(buf, c)

command.go

@@ -1056,7 +1056,25 @@ func (c *Command) InitDefaultHelpCmd() {
 			Short: "Help about any command",
 			Long: `Help provides help for any command in the application.
 Simply type ` + c.Name() + ` help [path to command] for full details.`,
-
+			ValidArgsFunction: func(c *Command, args []string, toComplete string) ([]string, ShellCompDirective) {
+				var completions []string
+				cmd, _, e := c.Root().Find(args)
+				if e != nil {
+					return nil, ShellCompDirectiveNoFileComp
+				}
+				if cmd == nil {
+					// Root help command.
+					cmd = c.Root()
+				}
+				for _, subCmd := range cmd.Commands() {
+					if subCmd.IsAvailableCommand() || subCmd == cmd.helpCommand {
+						if strings.HasPrefix(subCmd.Name(), toComplete) {
+							completions = append(completions, fmt.Sprintf("%s\t%s", subCmd.Name(), subCmd.Short))
+						}
+					}
+				}
+				return completions, ShellCompDirectiveNoFileComp
+			},
 			Run: func(c *Command, args []string) {
 				cmd, _, e := c.Root().Find(args)
 				if cmd == nil || e != nil {

custom_completions.go

@@ -183,12 +183,14 @@ func (c *Command) getCompletions(args []string) (*Command, []string, ShellCompDi
 	}
 
 	if flag == nil {
-		// Complete subcommand names
+		// Complete subcommand names, including the help command
 		for _, subCmd := range finalCmd.Commands() {
-			if subCmd.IsAvailableCommand() && strings.HasPrefix(subCmd.Name(), toComplete) {
+			if subCmd.IsAvailableCommand() || subCmd == finalCmd.helpCommand {
+				if strings.HasPrefix(subCmd.Name(), toComplete) {
 					completions = append(completions, fmt.Sprintf("%s\t%s", subCmd.Name(), subCmd.Short))
 				}
 			}
+		}
 
 		if len(finalCmd.ValidArgs) > 0 {
 			// Always complete ValidArgs, even if we are completing a subcommand name.

custom_completions_test.go

@@ -629,3 +629,71 @@ func TestFlagCompletionInGoWithDesc(t *testing.T) {
 		t.Errorf("expected: %q, got: %q", expected, output)
 	}
 }
+
+func TestCompleteHelp(t *testing.T) {
+	rootCmd := &Command{Use: "root", Args: NoArgs, Run: emptyRun}
+	child1Cmd := &Command{
+		Use: "child1",
+		Run: emptyRun,
+	}
+	child2Cmd := &Command{
+		Use: "child2",
+		Run: emptyRun,
+	}
+	rootCmd.AddCommand(child1Cmd, child2Cmd)
+
+	child3Cmd := &Command{
+		Use: "child3",
+		Run: emptyRun,
+	}
+	child1Cmd.AddCommand(child3Cmd)
+
+	// Test that completion includes the help command
+	output, err := executeCommand(rootCmd, ShellCompNoDescRequestCmd, "")
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	expected := strings.Join([]string{
+		"child1",
+		"child2",
+		"help",
+		":0",
+		"Completion ended with directive: ShellCompDirectiveDefault", ""}, "\n")
+
+	if output != expected {
+		t.Errorf("expected: %q, got: %q", expected, output)
+	}
+
+	// Test sub-commands are completed on first level of help command
+	output, err = executeCommand(rootCmd, ShellCompNoDescRequestCmd, "help", "")
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	expected = strings.Join([]string{
+		"child1",
+		"child2",
+		"help", // "<program> help help" is a valid command, so should be completed
+		":4",
+		"Completion ended with directive: ShellCompDirectiveNoFileComp", ""}, "\n")
+
+	if output != expected {
+		t.Errorf("expected: %q, got: %q", expected, output)
+	}
+
+	// Test sub-commands are completed on first level of help command
+	output, err = executeCommand(rootCmd, ShellCompNoDescRequestCmd, "help", "child1", "")
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	expected = strings.Join([]string{
+		"child3",
+		":4",
+		"Completion ended with directive: ShellCompDirectiveNoFileComp", ""}, "\n")
+
+	if output != expected {
+		t.Errorf("expected: %q, got: %q", expected, output)
+	}
+}