Object.observe: notify when element addition causes array growth

src/objects.cc

 // 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 10289 matching lines @@
     SeededNumberDictionary* dictionary;
     MaybeObject* maybe_object = NormalizeElements();
     if (!maybe_object->To(&dictionary)) return maybe_object;
     // Make sure that we never go back to fast case.
     dictionary->set_requires_slow_elements();
   }
 
   // From here on, everything has to be handlified.
   Handle<String> name;
   Handle<Object> old_value(isolate->heap()->the_hole_value());
+  Handle<Object> old_array_length;
   PropertyAttributes old_attributes = ABSENT;
   bool preexists = false;
   if (FLAG_harmony_observation && map()->is_observed()) {
     name = isolate->factory()->Uint32ToString(index);
     preexists = self->HasLocalElement(index);
     if (preexists) {
       old_attributes = self->GetLocalPropertyAttribute(*name);
       // TODO(observe): only read & set old_value if we have a data property
       old_value = Object::GetElement(self, index);
     }
+    // Store the old array length in case adding an element will grow the array.
+    if (!preexists && self->IsJSArray())

[rossberg, 2012/11/08 16:50:20]

Maybe make that an "else if (self->IsJSArray())"

[adamk, 2012/11/08 17:08:18]

Done.

+      old_array_length = handle(Handle<JSArray>::cast(self)->length());
   }
 
   // Check for lookup interceptor
   MaybeObject* result = self->HasIndexedInterceptor()
     ? self->SetElementWithInterceptor(
         index, *value, attributes, strict_mode, check_prototype, set_mode)
     : self->SetElementWithoutInterceptor(
         index, *value, attributes, strict_mode, check_prototype, set_mode);
 
   Handle<Object> hresult;
   if (!result->ToHandle(&hresult)) return result;
 
   if (FLAG_harmony_observation && map()->is_observed()) {
     PropertyAttributes new_attributes = self->GetLocalPropertyAttribute(*name);
     if (!preexists) {
+      if (self->IsJSArray() &&
+          !old_array_length->SameValue(Handle<JSArray>::cast(self)->length())) {
+        EnqueueChangeRecord(self, "updated",
+                            isolate->factory()->length_symbol(),
+                            old_array_length);
+      }
       EnqueueChangeRecord(self, "new", name, old_value);
     } else if (new_attributes != old_attributes || old_value->IsTheHole()) {
       EnqueueChangeRecord(self, "reconfigured", name, old_value);
     } else {
       Handle<Object> newValue = Object::GetElement(self, index);

[rossberg, 2012/11/08 16:50:20]

Not your change, but while you're at it, can you also fix this misspelling of
'newValue' I overlooked?

[adamk, 2012/11/08 17:08:18]

Fixed.

       if (!newValue->SameValue(*old_value))
         EnqueueChangeRecord(self, "updated", name, old_value);
     }
   }
 
   return *hresult;
 }
 
 
 MaybeObject* JSObject::SetElementWithoutInterceptor(uint32_t index,
@@ skipping 3497 matching lines @@
   set_year(Smi::FromInt(year), SKIP_WRITE_BARRIER);
   set_month(Smi::FromInt(month), SKIP_WRITE_BARRIER);
   set_day(Smi::FromInt(day), SKIP_WRITE_BARRIER);
   set_weekday(Smi::FromInt(weekday), SKIP_WRITE_BARRIER);
   set_hour(Smi::FromInt(hour), SKIP_WRITE_BARRIER);
   set_min(Smi::FromInt(min), SKIP_WRITE_BARRIER);
   set_sec(Smi::FromInt(sec), SKIP_WRITE_BARRIER);
 }
 
 } }  // namespace v8::internal