Deprecate 'return false' in event handlers

docs/docs/ref-05-events.md

@@ -27,6 +27,10 @@ Date timeStamp
 String type
 ```
 
+> Note:
+>
+> As of v0.12, returning `false` from an event handler will no longer stop event propagation. Instead, `e.stopPropagation()` or `e.preventDefault()` should be triggered manually, as appropriate.
+
 
 ## Supported Events
 
@@ -111,7 +115,7 @@ onDragOver onDragStart onDrop onMouseDown onMouseEnter onMouseLeave
 onMouseMove onMouseOut onMouseOver onMouseUp
 ```
 
-Properties: 
+Properties:
 
 ```javascript
 boolean altKey

src/browser/__tests__/ReactBrowserEventEmitter-test.js

@@ -253,7 +253,7 @@ describe('ReactBrowserEventEmitter', function() {
     expect(idCallOrder[0]).toBe(getID(CHILD));
   });
 
-  it('should stopPropagation if false is returned', function() {
+  it('should stopPropagation if false is returned, but warn', function() {
     ReactBrowserEventEmitter.putListener(
       getID(CHILD),
       ON_CLICK_KEY,
@@ -269,9 +269,16 @@ describe('ReactBrowserEventEmitter', function() {
       ON_CLICK_KEY,
       recordID.bind(null, getID(GRANDPARENT))
     );
+    spyOn(console, 'warn');
     ReactTestUtils.Simulate.click(CHILD);
     expect(idCallOrder.length).toBe(1);
     expect(idCallOrder[0]).toBe(getID(CHILD));
+    expect(console.warn.calls.length).toEqual(1);
+    expect(console.warn.calls[0].args[0]).toBe(
+      'Warning: Returning `false` from an event handler is deprecated and ' +
+      'will be ignored in a future release. Instead, manually call ' +
+      'e.stopPropagation() or e.preventDefault(), as appropriate.'
+    );
   });
 
   /**

src/browser/eventPlugins/SimpleEventPlugin.js

@@ -35,6 +35,7 @@ var getEventCharCode = require('getEventCharCode');
 
 var invariant = require('invariant');
 var keyOf = require('keyOf');
+var warning = require('warning');
 
 var topLevelTypes = EventConstants.topLevelTypes;
 
@@ -301,14 +302,22 @@ var SimpleEventPlugin = {
 
   /**
    * Same as the default implementation, except cancels the event when return
-   * value is false.
+   * value is false. This behavior will be disabled in a future release.
    *
    * @param {object} Event to be dispatched.
    * @param {function} Application-level callback.
    * @param {string} domID DOM ID to pass to the callback.
    */
   executeDispatch: function(event, listener, domID) {
     var returnValue = EventPluginUtils.executeDispatch(event, listener, domID);
+
+    warning(
+      typeof returnValue !== 'boolean',
+      'Returning `false` from an event handler is deprecated and will be ' +
+      'ignored in a future release. Instead, manually call ' +
+      'e.stopPropagation() or e.preventDefault(), as appropriate.'
+    );
+
     if (returnValue === false) {
       event.stopPropagation();
       event.preventDefault();