blob: 104327c9a05424287b44f816836606e1c66f7867 [file] [log] [blame]
// Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
import '../command_runner.dart';
/// The built-in help command that's added to every [CommandRunner].
/// This command displays help information for the various subcommands.
class HelpCommand<T> extends Command<T> {
final name = "help";
String get description =>
"Display help information for ${runner.executableName}.";
String get invocation => "${runner.executableName} help [command]";
T run() {
// Show the default help if no command was specified.
if ( {
return null;
// Walk the command tree to show help for the selected command or
// subcommand.
var commands = runner.commands;
Command command;
var commandString = runner.executableName;
for (var name in {
if (commands.isEmpty) {
'Command "$commandString" does not expect a subcommand.');
if (commands[name] == null) {
if (command == null) {
runner.usageException('Could not find a command named "$name".');
'Could not find a subcommand named "$name" for "$commandString".');
command = commands[name];
commands = command.subcommands;
commandString += " $name";
return null;