Added support for multi-valued options (options that can occur more than once).

tests/lib/args/args_test.dart

 // Copyright (c) 2012, 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.
 
 #library('args_test');
 
 #import('../../../lib/unittest/unittest.dart');
 #import('../../../lib/args/args.dart');
 
 main() {
@@ skipping 339 matching lines @@
         parser.addOption('mode', allowed: ['debug', 'release']);
         var args = parser.parse(['--mode=debug']);
         expect(args['mode'], equals('debug'));
       });
 
       test('throw if the value is not in the allowed set', () {
         var parser = new ArgParser();
         parser.addOption('mode', allowed: ['debug', 'release']);
         throwsFormat(parser, ['--mode=profile']);
       });
+
+      test('returns last provided value', () {
+        var parser = new ArgParser();
+        parser.addOption('define');
+        var args = parser.parse(['--define=1', '--define=2']);
+        expect(args['define'], equals('2'));
+      });
+
+      test('returns a List if multi-valued', () {
+        var parser = new ArgParser();
+        parser.addOption('define', allowMultiple: true);
+        var args = parser.parse(['--define=1']);
+        expect(args['define'], equals(['1']));
+        args = parser.parse(['--define=1', '--define=2']);
+        expect(args['define'], equals(['1','2']));
+      });
+
+      test('returns the default value for multi-valued arguments '
+           'if not explicitly set', () {
+        var parser = new ArgParser();
+        parser.addOption('define', defaultsTo:'0', allowMultiple: true);
+        var args = parser.parse(['']);
+        expect(args['define'], equals(['0']));
+      });
     });
 
     group('remaining args', () {
       test('stops parsing args when a non-option-like arg is encountered', () {
         var parser = new ArgParser();
         parser.addFlag('woof');
         parser.addOption('meow');
         parser.addOption('tweet', defaultsTo: 'bird');
 
         var results = parser.parse(['--woof', '--meow', 'v', 'not', 'option']);
@@ skipping 180 matching lines @@
   group('ArgResults[]', () {
     test('throws if the name is not an option', () {
       var parser = new ArgParser();
       var results = parser.parse([]);
       throwsIllegalArg(() => results['unknown']);
     });
   });
 }
 
 throwsIllegalArg(function) {
-  expect(function, throwsA(new isInstanceOf<IllegalArgumentException>()));
+  expect(function, throwsIllegalArgumentException);
 }
 
 throwsFormat(ArgParser parser, List<String> args) {
   expect(() => parser.parse(args), throwsFormatException);
 }
 
 validateUsage(ArgParser parser, String expected) {
   expected = unindentString(expected);
   expect(parser.getUsage(), equals(expected));
 }
@@ skipping 25 matching lines @@
         throw new IllegalArgumentException(
             'Line "$line" does not have enough indentation.');
       }
 
       lines[i] = line.substring(indent);
     }
   }
 
   return Strings.join(lines, '\n');
 }