Confusion on changing data property callback attributes

src/objects.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "v8.h"
 
 #include "accessors.h"
 #include "allocation-site-scopes.h"
 #include "api.h"
 #include "arguments.h"
@@ skipping 4300 matching lines @@
   return result;
 }
 
 
 // Set a real local property, even if it is READ_ONLY.  If the property is not
 // present, add it with attributes NONE.  This code is an exact clone of
 // SetProperty, with the check for IsReadOnly and the check for a
 // callback setter removed.  The two lines looking up the LookupResult
 // result are also added.  If one of the functions is changed, the other
 // should be.
-// Note that this method cannot be used to set the prototype of a function
-// because ConvertDescriptorToField() which is called in "case CALLBACKS:"
-// doesn't handle function prototypes correctly.
 MaybeHandle<Object> JSObject::SetLocalPropertyIgnoreAttributes(
     Handle<JSObject> object,
     Handle<Name> name,
     Handle<Object> value,
     PropertyAttributes attributes,
     ValueType value_type,
     StoreMode mode,
     ExtensibilityCheck extensibility_check,
-    StoreFromKeyed store_from_keyed) {
+    StoreFromKeyed store_from_keyed,
+    ExecutableAccessorInfoHandling handling) {
   Isolate* isolate = object->GetIsolate();
 
   // Make sure that the top context does not change when doing callbacks or
   // interceptor calls.
   AssertNoContextChange ncc(isolate);
 
   LookupResult lookup(isolate);
   object->LocalLookup(name, &lookup, true);
   if (!lookup.IsFound()) {
     object->map()->LookupTransition(*object, *name, &lookup);
@@ skipping 34 matching lines @@
   PropertyAttributes old_attributes = ABSENT;
   bool is_observed = object->map()->is_observed() &&
                      *name != isolate->heap()->hidden_string();
   if (is_observed && lookup.IsProperty()) {
     if (lookup.IsDataProperty()) {
       old_value = Object::GetPropertyOrElement(object, name).ToHandleChecked();
     }
     old_attributes = lookup.GetAttributes();
   }
 
+  bool dont_enqueue_records = false;
+
   // Check of IsReadOnly removed from here in clone.
   if (lookup.IsTransition()) {
     Handle<Object> result;
     ASSIGN_RETURN_ON_EXCEPTION(
         isolate, result,
         SetPropertyUsingTransition(
             handle(lookup.holder()), &lookup, name, value, attributes),
         Object);
   } else {
     switch (lookup.type()) {
       case NORMAL:
         ReplaceSlowProperty(object, name, value, attributes);
         break;
       case FIELD:
         SetPropertyToFieldWithAttributes(&lookup, name, value, attributes);
         break;
       case CONSTANT:
         // Only replace the constant if necessary.
         if (lookup.GetAttributes() != attributes ||
             *value != lookup.GetConstant()) {
           SetPropertyToFieldWithAttributes(&lookup, name, value, attributes);
         }
         break;
       case CALLBACKS:
-        ConvertAndSetLocalProperty(&lookup, name, value, attributes);
+      {
+        Handle<Object> callback(lookup.GetCallbackObject(), isolate);
+        if (callback->IsExecutableAccessorInfo() &&
+            handling == DONT_FORCE_FIELD) {
+          Handle<Object> result;
+          ASSIGN_RETURN_ON_EXCEPTION(
+              isolate, result,
+              JSObject::SetPropertyWithCallback(object,
+                                                callback,
+                                                name,
+                                                value,
+                                                handle(lookup.holder()),
+                                                STRICT),
+              Object);
+
+          if (attributes != lookup.GetAttributes()) {
+            Handle<ExecutableAccessorInfo> new_data =
+                Accessors::CloneAccessor(
+                    isolate, Handle<ExecutableAccessorInfo>::cast(callback));
+            new_data->set_property_attributes(attributes);
+            if (attributes & READ_ONLY) {
+              // This way we don't have to introduce a lookup to the setter,
+              // simply make it unavailable to reflect the attributes.
+              new_data->clear_setter();
+            }
+
+            SetPropertyCallback(object, name, new_data, attributes);
+          } else if (is_observed) {

[ulan, 2014/05/23 10:14:48]

Shouldn't we check is_observed independent of (attributes !=
lookup.GetAttributes()) ?

[mvstanton, 2014/05/27 13:31:24]

Good catch. And I renamed the variable from dont_enqueue_records to
executed_set_prototype when is less awkward. Basically setting the prototype is
the one exception for this "observed" infrastructure.

+            // If we are setting the prototype of a function and are observed,
+            // don't send change records because the prototype handles that
+            // itself.
+            dont_enqueue_records = object->IsJSFunction() &&
+                String::Equals(isolate->factory()->prototype_string(),
+                               Handle<String>::cast(name)) &&
+                Handle<JSFunction>::cast(object)->should_have_prototype();
+          }
+        } else {
+          ConvertAndSetLocalProperty(&lookup, name, value, attributes);
+        }
         break;
+      }
       case NONEXISTENT:
       case HANDLER:
       case INTERCEPTOR:
         UNREACHABLE();
     }
   }
 
-  if (is_observed) {
+  if (is_observed && !dont_enqueue_records) {
     if (lookup.IsTransition()) {
       EnqueueChangeRecord(object, "add", name, old_value);
     } else if (old_value->IsTheHole()) {
       EnqueueChangeRecord(object, "reconfigure", name, old_value);
     } else {
       LookupResult new_lookup(isolate);
       object->LocalLookup(name, &new_lookup, true);
       bool value_changed = false;
       if (new_lookup.IsDataProperty()) {
         Handle<Object> new_value =
@@ skipping 12845 matching lines @@
 #define ERROR_MESSAGES_TEXTS(C, T) T,
   static const char* error_messages_[] = {
       ERROR_MESSAGES_LIST(ERROR_MESSAGES_TEXTS)
   };
 #undef ERROR_MESSAGES_TEXTS
   return error_messages_[reason];
 }
 
 
 } }  // namespace v8::internal