Moved the Option class to its own file in anticipation of working on it.

pkg/args/lib/args.dart

 // Copyright (c) 2013, 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.
 
 /**
  * This library lets you define parsers for parsing raw command-line arguments
  * into a set of options and values using [GNU][] and [POSIX][] style options.
  *
  * ## Installing ##
  *
@@ skipping 239 matching lines @@
  * options.
  *
  * [posix]: http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap12.html#tag_12_02
  * [gnu]: http://www.gnu.org/prep/standards/standards.html#Command_002dLine-Interfaces
  * [pub]: http://pub.dartlang.org
  */
 library args;
 
 import 'src/parser.dart';
 import 'src/usage.dart';
+import 'src/options.dart';
+export 'src/options.dart';
 
 /**
  * A class for taking a list of raw command line arguments and parsing out
  * options and flags from them.
  */
 class ArgParser {
   /**
    * The options that have been defined for this parser.
    */
   final Map<String, Option> options = <String, Option>{};
@@ skipping 100 matching lines @@
    * Finds the option whose abbreviation is [abbr], or `null` if no option has
    * that abbreviation.
    */
   Option findByAbbreviation(String abbr) {
     return options.values.firstWhere((option) => option.abbreviation == abbr,
         orElse: () => null);
   }
 }
 
 /**
- * A command-line option. Includes both flags and options which take a value.
- */
-class Option {
-  final String name;
-  final String abbreviation;
-  final List<String> allowed;
-  final defaultValue;
-  final Function callback;
-  final String help;
-  final Map<String, String> allowedHelp;
-  final bool isFlag;
-  final bool negatable;
-  final bool allowMultiple;
-
-  Option(this.name, this.abbreviation, this.help, this.allowed,
-      this.allowedHelp, this.defaultValue, this.callback, {this.isFlag,
-      this.negatable, this.allowMultiple: false}) {
-
-    if (name.isEmpty) {
-      throw new ArgumentError('Name cannot be empty.');
-    } else if (name.startsWith('-')) {
-      throw new ArgumentError('Name $name cannot start with "-".');
-    }
-
-    // Ensure name does not contain any invalid characters.
-    if (_invalidChars.hasMatch(name)) {
-      throw new ArgumentError('Name "$name" contains invalid characters.');
-    }
-
-    if (abbreviation != null) {
-      if (abbreviation.length != 1) {
-        throw new ArgumentError('Abbreviation must be null or have length 1.');
-      } else if(abbreviation == '-') {
-        throw new ArgumentError('Abbreviation cannot be "-".');
-      }
-
-      if (_invalidChars.hasMatch(abbreviation)) {
-        throw new ArgumentError('Abbreviation is an invalid character.');
-      }
-    }
-  }
-
-  static final _invalidChars = new RegExp(r'''[ \t\r\n"'\\/]''');
-}
-
-/**
  * The results of parsing a series of command line arguments using
  * [ArgParser.parse()]. Includes the parsed options and any remaining unparsed
  * command line arguments.
  */
 class ArgResults {
   final Map _options;
 
   /**
    * If these are the results for parsing a command's options, this will be
    * the name of the command. For top-level results, this returns `null`.
@@ skipping 23 matching lines @@
           'Could not find an option named "$name".');
     }
 
     return _options[name];
   }
 
   /** Get the names of the options as an [Iterable]. */
   Iterable<String> get options => _options.keys;
 }