Make Object.freeze/seal/preventExtensions observable

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 114 matching lines @@
   }
 
   return true;
 }
 
 var defaultAcceptTypes = TypeMapCreateFromList([
   'new',
   'updated',
   'deleted',
   'prototype',
-  'reconfigured'
+  'reconfigured',
+  'preventExtensions'
 ]);
 
 // An Observer is a registration to observe an object by a callback with
 // a given set of accept types. If the set of accept types is the default
 // set for Object.observe, the observer is represented as a direct reference
 // to the callback. An observer never changes its accept types and thus never
 // needs to "normalize".
 function ObserverCreate(callback, acceptList) {
   return IS_UNDEFINED(acceptList) ? callback : {
     __proto__: null,
@@ skipping 290 matching lines @@
   ObjectFreeze(changeRecord);
   ObjectFreeze(changeRecord.removed);
   ObjectInfoEnqueueChangeRecord(objectInfo, changeRecord);
 }
 
 function NotifyChange(type, object, name, oldValue) {
   var objectInfo = objectInfoMap.get(object);
   if (!ObjectInfoHasActiveObservers(objectInfo))
     return;
 
-  var changeRecord = (arguments.length < 4) ?
-      { type: type, object: object, name: name } :
-      { type: type, object: object, name: name, oldValue: oldValue };
+  var changeRecord;

[rossberg, 2013/10/30 19:11:45]

I think you can write this more concisely as follows:

var changeRecord = { type: type, object: object };
if (arguments.length >= 3) changeRecord.name = name;
if (arguments.length >= 4) changeRecord.oldValue = oldValue;

[rafaelw, 2013/10/30 23:00:30]

We need the changeRecord object to have the default object proto, so only using
literals avoids monkey patches to Object.proto interfering here.

On 2013/10/30 19:11:45, rossberg wrote:

+  if (arguments.length == 2) {
+    changeRecord = { type: type, object: object };
+  } else if (arguments.length == 3) {
+    changeRecord = { type: type, object: object, name: name };
+  } else {
+    changeRecord = {
+      type: type,
+      object: object,
+      name: name,
+      oldValue: oldValue
+    };
+  }
+
   ObjectFreeze(changeRecord);
   ObjectInfoEnqueueChangeRecord(objectInfo, changeRecord);
 }
 
 var notifierPrototype = {};
 
 function ObjectNotifierNotify(changeRecord) {
   if (!IS_SPEC_OBJECT(this))
     throw MakeTypeError("called_on_non_object", ["notify"]);
 
@@ skipping 100 matching lines @@
     "observe", ArrayObserve,
     "unobserve", ArrayUnobserve
   ));
   InstallFunctions(notifierPrototype, DONT_ENUM, $Array(
     "notify", ObjectNotifierNotify,
     "performChange", ObjectNotifierPerformChange
   ));
 }
 
 SetupObjectObserve();