Merge pull request #2054 from chenglou/accum

[RFC] Use `accumulateInto` to save even more allocation

src/browser/eventPlugins/ResponderEventPlugin.js

@@ -23,7 +23,7 @@ var EventPluginUtils = require('EventPluginUtils');
 var EventPropagators = require('EventPropagators');
 var SyntheticEvent = require('SyntheticEvent');
 
-var accumulate = require('accumulate');
+var accumulateInto = require('accumulateInto');
 var keyOf = require('keyOf');
 
 var isStartish = EventPluginUtils.isStartish;
@@ -212,7 +212,7 @@ function setResponderAndExtractTransfer(
         nativeEvent
       );
       EventPropagators.accumulateDirectDispatches(terminateEvent);
-      extracted = accumulate(extracted, [grantEvent, terminateEvent]);
+      extracted = accumulateInto(extracted, [grantEvent, terminateEvent]);
       responderID = wantsResponderID;
     } else {
       var rejectEvent = SyntheticEvent.getPooled(
@@ -221,10 +221,10 @@ function setResponderAndExtractTransfer(
         nativeEvent
       );
       EventPropagators.accumulateDirectDispatches(rejectEvent);
-      extracted = accumulate(extracted, rejectEvent);
+      extracted = accumulateInto(extracted, rejectEvent);
     }
   } else {
-    extracted = accumulate(extracted, grantEvent);
+    extracted = accumulateInto(extracted, grantEvent);
     responderID = wantsResponderID;
   }
   return extracted;
@@ -288,7 +288,7 @@ var ResponderEventPlugin = {
         nativeEvent
       );
       if (transfer) {
-        extracted = accumulate(extracted, transfer);
+        extracted = accumulateInto(extracted, transfer);
       }
     }
     // Now that we know the responder is set correctly, we can dispatch
@@ -303,7 +303,7 @@ var ResponderEventPlugin = {
         nativeEvent
       );
       EventPropagators.accumulateDirectDispatches(gesture);
-      extracted = accumulate(extracted, gesture);
+      extracted = accumulateInto(extracted, gesture);
     }
     if (type === eventTypes.responderRelease) {
       responderID = null;

src/browser/ui/dom/components/LocalEventTrapMixin.js

@@ -20,7 +20,7 @@
 
 var ReactBrowserEventEmitter = require('ReactBrowserEventEmitter');
 
-var accumulate = require('accumulate');
+var accumulateInto = require('accumulateInto');
 var forEachAccumulated = require('forEachAccumulated');
 var invariant = require('invariant');
 
@@ -36,7 +36,8 @@ var LocalEventTrapMixin = {
       handlerBaseName,
       this.getDOMNode()
     );
-    this._localEventListeners = accumulate(this._localEventListeners, listener);
+    this._localEventListeners =
+      accumulateInto(this._localEventListeners, listener);
   },
 
   // trapCapturedEvent would look nearly identical. We don't implement that

src/event/EventPluginHub.js

@@ -21,7 +21,7 @@
 var EventPluginRegistry = require('EventPluginRegistry');
 var EventPluginUtils = require('EventPluginUtils');
 
-var accumulate = require('accumulate');
+var accumulateInto = require('accumulateInto');
 var forEachAccumulated = require('forEachAccumulated');
 var invariant = require('invariant');
 var isEventSupported = require('isEventSupported');
@@ -236,7 +236,7 @@ var EventPluginHub = {
           nativeEvent
         );
         if (extractedEvents) {
-          events = accumulate(events, extractedEvents);
+          events = accumulateInto(events, extractedEvents);
         }
       }
     }
@@ -252,7 +252,7 @@ var EventPluginHub = {
    */
   enqueueEvents: function(events) {
     if (events) {
-      eventQueue = accumulate(eventQueue, events);
+      eventQueue = accumulateInto(eventQueue, events);
     }
   },
 

src/event/EventPropagators.js

@@ -21,7 +21,7 @@
 var EventConstants = require('EventConstants');
 var EventPluginHub = require('EventPluginHub');
 
-var accumulate = require('accumulate');
+var accumulateInto = require('accumulateInto');
 var forEachAccumulated = require('forEachAccumulated');
 
 var PropagationPhases = EventConstants.PropagationPhases;
@@ -52,8 +52,9 @@ function accumulateDirectionalDispatches(domID, upwards, event) {
   var phase = upwards ? PropagationPhases.bubbled : PropagationPhases.captured;
   var listener = listenerAtPhase(domID, event, phase);
   if (listener) {
-    event._dispatchListeners = accumulate(event._dispatchListeners, listener);
-    event._dispatchIDs = accumulate(event._dispatchIDs, domID);
+    event._dispatchListeners =
+      accumulateInto(event._dispatchListeners, listener);
+    event._dispatchIDs = accumulateInto(event._dispatchIDs, domID);
   }
 }
 
@@ -85,8 +86,9 @@ function accumulateDispatches(id, ignoredDirection, event) {
     var registrationName = event.dispatchConfig.registrationName;
     var listener = getListener(id, registrationName);
     if (listener) {
-      event._dispatchListeners = accumulate(event._dispatchListeners, listener);
-      event._dispatchIDs = accumulate(event._dispatchIDs, id);
+      event._dispatchListeners =
+        accumulateInto(event._dispatchListeners, listener);
+      event._dispatchIDs = accumulateInto(event._dispatchIDs, id);
     }
   }
 }

src/utils/__tests__/accumulateInto-test.js

@@ -0,0 +1,64 @@
+/**
+ * Copyright 2014 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * @emails react-core
+ * @jsx React.DOM
+ */
+
+"use strict";
+
+require('mock-modules')
+  .dontMock('accumulateInto');
+
+var accumulateInto;
+
+describe('accumulateInto', function() {
+
+  beforeEach(function() {
+    accumulateInto = require('accumulateInto');
+  });
+
+  it('throws if the second item is null', function() {
+    expect(function() {
+      accumulateInto([], null);
+    }).toThrow(
+      'Invariant Violation: accumulateInto(...): Accumulated items must not ' +
+      'be null or undefined.'
+    );
+  });
+
+  it('returns the second item if first is null', function() {
+    var a = [];
+    expect(accumulateInto(null, a)).toBe(a);
+  });
+
+  it('merges the second into the first if first item is an array', function() {
+    var a = [1, 2];
+    var b = [3, 4];
+    accumulateInto(a, b);
+    expect(a).toEqual([1, 2, 3, 4]);
+    expect(b).toEqual([3, 4]);
+    var c = [1];
+    accumulateInto(c, 2);
+    expect(c).toEqual([1, 2]);
+  });
+
+  it('returns a new array if first or both items are scalar', function() {
+    var a = [2];
+    expect(accumulateInto(1, a)).toEqual([1, 2]);
+    expect(a).toEqual([2]);
+    expect(accumulateInto(1, 2)).toEqual([1, 2]);
+  });
+});

src/utils/accumulateInto.js

@@ -0,0 +1,69 @@
+/**
+ * Copyright 2014 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * @providesModule accumulateInto
+ */
+
+"use strict";
+
+var invariant = require('invariant');
+
+/**
+ *
+ * Accumulates items that must not be null or undefined into the first one. This
+ * is used to conserve memory by avoiding array allocations, and thus sacrifices
+ * API cleanness. Since `current` can be null before being passed in and not
+ * null after this function, make sure to assign it back to `current`:
+ *
+ * `a = accumulateInto(a, b);`
+ *
+ * This API should be sparingly used. Try `accumulate` for something cleaner.
+ *
+ * @return {*|array<*>} An accumulation of items.
+ */
+
+function accumulateInto(current, next) {
+  invariant(
+    next != null,
+    'accumulateInto(...): Accumulated items must not be null or undefined.'
+  );
+  if (current == null) {
+    return next;
+  }
+
+  // Both are not empty. Warning: Never call x.concat(y) when you are not
+  // certain that x is an Array (x could be a string with concat method).
+  var currentIsArray = Array.isArray(current);
+  var nextIsArray = Array.isArray(next);
+
+  if (currentIsArray && nextIsArray) {
+    current.push.apply(current, next);
+    return current;
+  }
+
+  if (currentIsArray) {
+    current.push(next);
+    return current;
+  }
+
+  if (nextIsArray) {
+    // A bit too dangerous to mutate `next`.
+    return [current].concat(next);
+  }
+
+  return [current, next];
+}
+
+module.exports = accumulateInto;