Allow command ArgParsers to be overridden.

lib/command_runner.dart

 // 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 'dart:async';
 import 'dart:collection';
 import 'dart:math' as math;
 
 import 'src/arg_parser.dart';
 import 'src/arg_results.dart';
@@ skipping 49 matching lines @@
 
   /// An unmodifiable view of all top-level commands defined for this runner.
   Map<String, Command> get commands => new UnmodifiableMapView(_commands);
   final _commands = <String, Command>{};
 
   /// The top-level argument parser.
   ///
   /// Global options should be registered with this parser; they'll end up
   /// available via [Command.globalResults]. Commands should be registered with
   /// [addCommand] rather than directly on the parser.
-  final argParser = new ArgParser();
+  ArgParser get argParser => _argParser;
+  final _argParser = new ArgParser();
 
   CommandRunner(this.executableName, this.description) {
     argParser.addFlag('help',
         abbr: 'h', negatable: false, help: 'Print this usage information.');
     addCommand(new HelpCommand());
   }
 
   /// Prints the usage information for this runner.
   ///
   /// This is called internally by [run] and can be overridden by subclasses to
@@ skipping 161 matching lines @@
   /// This will be `null` until just before [Command.run] is called.
   ArgResults get argResults => _argResults;
   ArgResults _argResults;
 
   /// The argument parser for this command.
   ///
   /// Options for this command should be registered with this parser (often in
   /// the constructor); they'll end up available via [argResults]. Subcommands
   /// should be registered with [addSubcommand] rather than directly on the
   /// parser.
-  final argParser = new ArgParser();
+  ArgParser get argParser => _argParser;
+  final _argParser = new ArgParser();
 
   /// Generates a string displaying usage information for this command.
   ///
   /// This includes usage for the command's arguments as well as a list of
   /// subcommands, if there are any.
   String get usage => "$description\n\n$_usageWithoutDescription";
 
   /// An optional footer for [usage].
   ///
   /// If a subclass overrides this to return a string, it will automatically be
@@ skipping 120 matching lines @@
 
     for (var line in lines.skip(1)) {
       buffer.writeln();
       buffer.write(' ' * (length + 5));
       buffer.write(line);
     }
   }
 
   return buffer.toString();
 }