[pkg:observe] Add support for explicit change notification, even on dirty-checked objects

pkg/observe/lib/src/change_notifier.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.
 
 part of observe;
 
 /**
- * Interface representing an [Observable] object that performs its own change
+ * Base class implementing [Observable] object that performs its own change
  * notifications, and does not need to be considered by [Observable.dirtyCheck].
- */
-abstract class ChangeNotifier extends Observable {
-  /**
-   * Notify observers of a change.
-   *
-   * For most objects [ChangeNotifierMixin.notifyPropertyChange] is more
-   * convenient, but collections sometimes deliver other types of changes such
-   * as a [ListChangeRecord].
-   */
-  void notifyChange(ChangeRecord record);
-}
-
-/**
- * Base class implementing [ChangeNotifier].
  *
  * When a field, property, or indexable item is changed, a derived class should
  * call [notifyPropertyChange]. See that method for an example.
  */
 typedef ChangeNotifierBase = Object with ChangeNotifierMixin;
 
 /**
- * Mixin for implementing [ChangeNotifier] objects.
+ * Mixin implementing [Observable] object that performs its own change
+ * notifications, and does not need to be considered by [Observable.dirtyCheck].
  *
  * When a field, property, or indexable item is changed, a derived class should
  * call [notifyPropertyChange]. See that method for an example.
  */
-abstract class ChangeNotifierMixin implements ChangeNotifier {
+abstract class ChangeNotifierMixin implements Observable {
   StreamController _changes;
   List<ChangeRecord> _records;
 
   Stream<List<ChangeRecord>> get changes {
     if (_changes == null) {
       _changes = new StreamController.broadcast(sync: true,
           onListen: _observed, onCancel: _unobserved);
     }
     return _changes.stream;
   }
 
   // TODO(jmesserly): should these be public? They're useful lifecycle methods
   // for subclasses. Ideally they'd be protected.
   /**
    * Override this method to be called when the [changes] are first observed.
    */
   void _observed() {}
 
   /**
    * Override this method to be called when the [changes] are no longer being
    * observed.
    */
   void _unobserved() {}
 
   bool deliverChanges() {
     var records = _records;
     _records = null;
     if (hasObservers && records != null) {
-      // TODO(jmesserly): make "records" immutable
-      _changes.add(records);
+      _changes.add(new UnmodifiableListView<ChangeRecord>(records));
       return true;
     }
     return false;
   }
 
   /**
    * True if this object has any observers, and should call
    * [notifyPropertyChange] for changes.
    */
   bool get hasObservers => _changes != null && _changes.hasListener;
 
   /**
    * Notify that the field [name] of this object has been changed.
    *
    * The [oldValue] and [newValue] are also recorded. If the two values are
    * identical, no change will be recorded.
    *
    * For convenience this returns [newValue]. This makes it easy to use in a
    * setter:
    *
    *     var _myField;
    *     get myField => _myField;
    *     set myField(value) {
    *       _myField = notifyPropertyChange(
    *           const Symbol('myField'), _myField, value);
    *     }
    */
-  // TODO(jmesserly): should this be == instead of identical, to prevent
-  // spurious loops?
-  notifyPropertyChange(Symbol field, Object oldValue, Object newValue) {
-    if (hasObservers && !identical(oldValue, newValue)) {
-      notifyChange(new PropertyChangeRecord(field));
-    }
-    return newValue;
-  }
+  notifyPropertyChange(Symbol field, Object oldValue, Object newValue)
+      => _notifyPropertyChange(this, field, oldValue, newValue);
 
   void notifyChange(ChangeRecord record) {
     if (!hasObservers) return;
 
     if (_records == null) {
       _records = [];
       runAsync(deliverChanges);
     }
     _records.add(record);
   }
 }