change addOption callback argument from bool to Dynamic

pkg/args/test/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('../../unittest/unittest.dart');
 
 // TODO(rnystrom): Use "package:" URL here when test.dart can handle pub.
 #import('../lib/args.dart');
@@ skipping 171 matching lines @@
       });
 
       test('are invoked even if the option is not present', () {
         var a = 'not called';
         var parser = new ArgParser();
         parser.addOption('a', callback: (value) => a = value);
 
         var args = parser.parse([]);
         expect(a, isNull);
       });
+      
+      test('for multiple present, allowMultiple, options are invoked with '
+          'value as a list', () {
+        var a;
+        var parser = new ArgParser();
+        parser.addOption('a', allowMultiple: true, 
+            callback: (value) => a = value);
+          
+        var args = parser.parse(['--a=v', '--a=x']);
+        expect(a, equals(['v', 'x']));
+      });
+      
+      test('for single present, allowMultiple, options are invoked with '
+          ' value as a single element list', () {
+        var a;
+        var parser = new ArgParser();
+        parser.addOption('a', allowMultiple: true,
+            callback: (value) => a = value);
+        
+        var args = parser.parse(['--a=v']);
+        expect(a, equals(['v']));
+      });
+      
+      test('for absent, allowMultiple, options are invoked with default '
+          'value as a list.', () {
+        var a;
+        var parser = new ArgParser();
+        parser.addOption('a', allowMultiple: true, defaultsTo: 'v',
+            callback: (value) => a = value);
+        
+        var args = parser.parse([]);
+        expect(a, equals(['v']));
+      });
+      
+      test('for absent, allowMultiple, options are invoked with value '
+          'as an empty list.', () {
+        var a;
+        var parser = new ArgParser();
+        parser.addOption('a', allowMultiple: true,
+            callback: (value) => a = value);
+        
+        var args = parser.parse([]);
+        expect(a, isEmpty);
+      });
     });
 
     group('abbreviations', () {
       test('are parsed with a preceding "-"', () {
         var parser = new ArgParser();
         parser.addFlag('arg', abbr: 'a');
 
         var args = parser.parse(['-a']);
         expect(args['arg'], isTrue);
       });
@@ skipping 457 matching lines @@
         throw new IllegalArgumentException(
             'Line "$line" does not have enough indentation.');
       }
 
       lines[i] = line.substring(indent);
     }
   }
 
   return Strings.join(lines, '\n');
 }