[observe] provide notifications of keys/values changed for ObservableMap

pkg/polymer_expressions/test/bindings_test.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.
 
 library bindings_test;
 
 import 'dart:async';
 import 'dart:html';
 
 import 'package:observe/observe.dart';
@@ skipping 29 matching lines @@
         expect(binding.value, 'hi');
       });
     });
 
     test('should update text content when data changes', () {
       var model = new NotifyModel('abcde');
       var template = templateBind(new Element.html(
           '<template><span>{{x}}</span></template>'));
       testDiv.append(template.createInstance(model, new PolymerExpressions()));
 
+      var el;
       return new Future(() {
-        var el = testDiv.query("span");
+        el = testDiv.query("span");
         expect(el.text, 'abcde');
         expect(model.x, 'abcde');
         model.x = '___';
-
-        return new Future(() {
-          expect(model.x, '___');
-          expect(el.text, '___');
-        });
+      }).then(_nextMicrotask).then((_) {
+        expect(model.x, '___');
+        expect(el.text, '___');
       });
     });
 
     test('should log eval exceptions', () {
       var model = new NotifyModel('abcde');
       var completer = new Completer();
       runZoned(() {
         var template = templateBind(new Element.html(
             '<template><span>{{foo}}</span></template>'));
         testDiv.append(template.createInstance(model,
             new PolymerExpressions()));
 
-        return new Future(() {});
+        return _nextMicrotask(null);
       }, onError: (e) {
         expect('$e', startsWith("Error evaluating expression 'foo':"));
         completer.complete(true);
       });
       return completer.future;
     });
 
     test('should preserve the cursor position', () {
       var model = new NotifyModel('abcde');
       var template = templateBind(new Element.html(
@@ skipping 28 matching lines @@
         expect(el.value, 'abc de');
 
         // But propagating observable values through reassign the value and
         // selection will be preserved.
         expect(el.selectionStart, 4);
         expect(el.selectionEnd, 4);
 
         subscription.cancel();
       });
     });
+
+
+    test('detects changes to ObservableMap keys/values', () {
+      var map = new ObservableMap.from({'a': 1, 'b': 2});
+      var template = templateBind(new Element.html('<template>'
+          '<template repeat="{{k in x.keys}}">{{k}}:{{x[k]}},</template>'
+          '</template>'));
+      var model = new NotifyModel(map);
+      testDiv.append(template.createInstance(model, new PolymerExpressions()));
+
+      return new Future(() {
+        expect(testDiv.text, 'a:1,b:2,');
+        map.remove('b');
+        map['c'] = 3;
+      }).then(_nextMicrotask).then((_) {
+        expect(testDiv.text, 'a:1,c:3,');
+        map['a'] = 4;
+      }).then(_nextMicrotask).then((_) {
+        expect(testDiv.text, 'a:4,c:3,');
+      });
+    });
   });
 });
 
+_nextMicrotask(_) => new Future(() {});
+
 @reflectable
 class NotifyModel extends ChangeNotifier {
   var _x;
   NotifyModel([this._x]);
 
   get x => _x;
   set x(value) {
     _x = notifyPropertyChange(#x, _x, value);
   }
 }