warn(SyntheticEvent): Warn when accessing or setting properties on re…

…leased syntheticEvents

src/renderers/dom/client/syntheticEvents/SyntheticEvent.js

@@ -156,13 +156,45 @@ assign(SyntheticEvent.prototype, {
    * `PooledClass` looks for `destructor` on each instance it releases.
    */
   destructor: function() {
+    var setNull = setToNullOrWarning.bind(this)
     var Interface = this.constructor.Interface;
     for (var propName in Interface) {
-      this[propName] = null;
+      setNull(propName);
+    }
+    var otherProps = ['dispatchConfig', '_targetInst', 'nativeEvent'];
+    otherProps.forEach(setNull);
+
+    function setToNullOrWarning(propName) {
+      if (__DEV__) {
+        Object.defineProperty(this, propName, {
+          set: function(val) {
+            // no-op
+            var warningCondition = false;
+            warning(
+              warningCondition,
+              'This synthetic event is reused for performance reasons. If you\'re ' +
+              'seeing this, you\'re setting property `' + propName + '` on a ' +
+              'released/nullified synthetic event. This is effectively a no-op. See ' +
+              'https://fb.me/react-event-pooling for more information.'
+            );
+            return val;
+          },
+          get: function() {
+            var warningCondition = false;
+            warning(
+              warningCondition,
+              'This synthetic event is reused for performance reasons. If you\'re ' +
+              'seeing this, you\'re accessing property `' + propName + '` on a ' +
+              'released/nullified synthetic event. This is set to null. See ' +
+              'https://fb.me/react-event-pooling for more information.'
+            );
+            return null;
+          }
+        })
+      } else {
+        this[propName] = null;
+      }
     }
-    this.dispatchConfig = null;
-    this._targetInst = null;
-    this.nativeEvent = null;
   },
 
 });

src/renderers/dom/client/syntheticEvents/__tests__/SyntheticEvent-test.js

@@ -73,6 +73,7 @@ describe('SyntheticEvent', function() {
   });
 
   it('should be nullified if the synthetic event has called destructor', function() {
+    spyOn(console, 'error');
     var target = document.createElement('div');
     var syntheticEvent = createEvent({srcElement: target});
     syntheticEvent.destructor();
@@ -81,27 +82,57 @@ describe('SyntheticEvent', function() {
     expect(syntheticEvent.target).toBe(null);
   });
 
+  it('should warn when accessing properties of a destructored synthetic event', function() {
+    spyOn(console, 'error');
+    var target = document.createElement('div');
+    var syntheticEvent = createEvent({srcElement: target});
+    syntheticEvent.destructor();
+    expect(syntheticEvent.type).toBe(null);
+    expect(console.error.calls.length).toBe(1);
+    expect(console.error.argsForCall[0][0]).toBe(
+      'Warning: This synthetic event is reused for performance reasons. If ' +
+      'you\'re seeing this, you\'re accessing a property on a ' +
+      'released/nullified synthetic event. This is set to null. See ' +
+      'https://fb.me/react-event-pooling for more information.'
+    );
+  });
+
+  it('should warn when setting properties of a destructored synthetic event', function() {
+    spyOn(console, 'error');
+    var target = document.createElement('div');
+    var syntheticEvent = createEvent({srcElement: target});
+    syntheticEvent.destructor();
+    expect(syntheticEvent.type = 'MouseEvent').toBe('MouseEvent');
+    expect(console.error.calls.length).toBe(1);
+    expect(console.error.argsForCall[0][0]).toBe(
+      'Warning: This synthetic event is reused for performance reasons. If ' +
+      'you\'re seeing this, you\'re setting a property on a ' +
+      'released/nullified synthetic event. This is effectively a no-op. See ' +
+      'https://fb.me/react-event-pooling for more information.'
+    );
+  });
+
   it('should warn if the synthetic event has been released when calling `preventDefault`', function() {
     spyOn(console, 'error');
     var syntheticEvent = createEvent({});
     SyntheticEvent.release(syntheticEvent);
     syntheticEvent.preventDefault();
-    expect(console.error.calls.length).toBe(1);
-    expect(console.error.argsForCall[0][0]).toBe(
+    expect(console.error.calls.length).toBe(3); // once each for setting `defaultPrevented`, accessing `nativeEvent`, and accessing `preventDefault`
+    expect(console.error.argsForCall[2][0]).toBe(
       'Warning: This synthetic event is reused for performance reasons. If ' +
       'you\'re seeing this, you\'re calling `preventDefault` on a ' +
       'released/nullified synthetic event. This is a no-op. See ' +
       'https://fb.me/react-event-pooling for more information.'
     );
   });
 
-  it('should warn if the synthetic event has been released when calling `stopPropagation`', function() {
+  iit('should warn if the synthetic event has been released when calling `stopPropagation`', function() {
     spyOn(console, 'error');
     var syntheticEvent = createEvent({});
     SyntheticEvent.release(syntheticEvent);
     syntheticEvent.stopPropagation();
-    expect(console.error.calls.length).toBe(1);
-    expect(console.error.argsForCall[0][0]).toBe(
+    expect(console.error.calls.length).toBe(2); // once each for accessing `nativeEvent` and accessing `setPropogation`
+    expect(console.error.argsForCall[1][0]).toBe(
       'Warning: This synthetic event is reused for performance reasons. If ' +
       'you\'re seeing this, you\'re calling `stopPropagation` on a ' +
       'released/nullified synthetic event. This is a no-op. See ' +