Implement Array.observe and emit splice change records for ArrayPush

src/object-observe.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 148 matching lines @@
 
 function EndPerformChange(objectInfo, type) {
   objectInfo.performing[type]--;
   objectInfo.performingCount--;
   RepartitionObservers(ObserverIsActive,
                        objectInfo.inactiveObservers,
                        objectInfo.changeObservers,
                        objectInfo);
 }
 
-function ensureObserverRemoved(objectInfo, callback) {
+function EnsureObserverRemoved(objectInfo, callback) {
   function remove(observerList) {
     for (var i = 0; i < observerList.length; i++) {
       if (observerList[i].callback === callback) {
         observerList.splice(i, 1);
         return true;
       }
     }
     return false;
   }
 
@@ skipping 32 matching lines @@
     observerInfoMap.set(callback, {
       pendingChangeRecords: null,
       priority: observationState.observerPriority++,
     });
   }
 
   var objectInfo = objectInfoMap.get(object);
   if (IS_UNDEFINED(objectInfo)) objectInfo = CreateObjectInfo(object);
   %SetIsObserved(object, true);
 
-  ensureObserverRemoved(objectInfo, callback);
+  EnsureObserverRemoved(objectInfo, callback);
 
   var observer = CreateObserver(callback, accept);
   if (ObserverIsActive(observer, objectInfo))
     objectInfo.changeObservers.push(observer);
   else
     objectInfo.inactiveObservers.push(observer);
 
   return object;
 }
 
 function ObjectUnobserve(object, callback) {
   if (!IS_SPEC_OBJECT(object))
     throw MakeTypeError("observe_non_object", ["unobserve"]);
   if (!IS_SPEC_FUNCTION(callback))
     throw MakeTypeError("observe_non_function", ["unobserve"]);
 
   var objectInfo = objectInfoMap.get(object);
   if (IS_UNDEFINED(objectInfo))
     return object;
 
-  ensureObserverRemoved(objectInfo, callback);
+  EnsureObserverRemoved(objectInfo, callback);
 
   if (objectInfo.changeObservers.length === 0 &&
       objectInfo.inactiveObservers.length === 0) {
     %SetIsObserved(object, false);
   }
 
   return object;
 }
 
+function ArrayObserve(object, callback) {
+  return ObjectObserve(object, callback, ['new',
+                                          'updated',
+                                          'deleted',
+                                          'splice']);
+}
+
+function ArrayUnobserve(object, callback) {
+  return ObjectUnobserve(object, callback);
+}
+
 function EnqueueChangeRecord(changeRecord, observers) {
   // TODO(rossberg): adjust once there is a story for symbols vs proxies.
   if (IS_SYMBOL(changeRecord.name)) return;
 
   for (var i = 0; i < observers.length; i++) {
     var observer = observers[i];
     if (IS_UNDEFINED(observer.accept[changeRecord.type]))
       continue;
 
     var callback = observer.callback;
     var observerInfo = observerInfoMap.get(callback);
     observationState.pendingObservers[observerInfo.priority] = callback;
     %SetObserverDeliveryPending();
     if (IS_NULL(observerInfo.pendingChangeRecords)) {
       observerInfo.pendingChangeRecords = new InternalArray(changeRecord);
     } else {
       observerInfo.pendingChangeRecords.push(changeRecord);
     }
   }
 }
 
+function BeginPerformSplice(array) {
+  var objectInfo = objectInfoMap.get(array);
+  if (!IS_UNDEFINED(objectInfo))
+    BeginPerformChange(objectInfo, 'splice');
+}
+
+function EndPerformSplice(array) {
+  var objectInfo = objectInfoMap.get(array);
+  if (!IS_UNDEFINED(objectInfo))
+    EndPerformChange(objectInfo, 'splice');
+}
+
+function EnqueueSpliceRecord(array, index, removed, deleteCount, addedCount) {
+  var objectInfo = objectInfoMap.get(array);
+  if (IS_UNDEFINED(objectInfo) || objectInfo.changeObservers.length === 0)
+    return;
+
+  var changeRecord = {
+    type: 'splice',
+    object: array,
+    index: index,
+    removed: removed,
+    addedCount: addedCount
+  };
+
+  changeRecord.removed.length = deleteCount;
+  // TODO(rafaelw): This breaks spec-compliance. Re-enable when freezing isn't
+  // slow.
+  // ObjectFreeze(changeRecord);
+  // ObjectFreeze(changeRecord.removed);
+  EnqueueChangeRecord(changeRecord, objectInfo.changeObservers);
+}
+
 function NotifyChange(type, object, name, oldValue) {
   var objectInfo = objectInfoMap.get(object);
   if (objectInfo.changeObservers.length === 0)
     return;
 
   var changeRecord = (arguments.length < 4) ?
       { type: type, object: object, name: name } :
       { type: type, object: object, name: name, oldValue: oldValue };
   // TODO(rafaelw): This breaks spec-compliance. Re-enable when freezing isn't
   // slow.
@@ skipping 114 matching lines @@
 }
 
 function SetupObjectObserve() {
   %CheckIsBootstrapping();
   InstallFunctions($Object, DONT_ENUM, $Array(
     "deliverChangeRecords", ObjectDeliverChangeRecords,
     "getNotifier", ObjectGetNotifier,
     "observe", ObjectObserve,
     "unobserve", ObjectUnobserve
   ));
+  InstallFunctions($Array, DONT_ENUM, $Array(
+    "observe", ArrayObserve,
+    "unobserve", ArrayUnobserve
+  ));
   InstallFunctions(notifierPrototype, DONT_ENUM, $Array(
     "notify", ObjectNotifierNotify,
     "performChange", ObjectNotifierPerformChange
   ));
 }
 
 SetupObjectObserve();