[esnext] implement Object.getOwnPropertyDescriptors() proposal

src/builtins.cc

 // Copyright 2012 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 "src/builtins.h"
 
 #include "src/api.h"
 #include "src/api-natives.h"
 #include "src/arguments.h"
 #include "src/base/once.h"
@@ skipping 1782 matching lines @@
     auto entry_storage = isolate->factory()->NewUninitializedFixedArray(2);
     entry_storage->set(0, *key);
     entry_storage->set(1, *value);
     auto entry = isolate->factory()->NewJSArrayWithElements(entry_storage);
     keys->set(i, *entry);
   }
 
   return *isolate->factory()->NewJSArrayWithElements(keys);
 }
 
+BUILTIN(ObjectGetOwnPropertyDescriptors) {
+  HandleScope scope(isolate);
+  Handle<Object> object = args.atOrUndefined(isolate, 1);
+  Handle<Object> undefined = isolate->factory()->undefined_value();
+
+  Handle<JSReceiver> receiver;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, receiver,
+                                     Object::ToObject(isolate, object));
+
+  Handle<FixedArray> keys;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, keys, JSReceiver::GetKeys(receiver, OWN_ONLY, ALL_PROPERTIES,
+                                         CONVERT_TO_STRING));
+
+  Handle<Object> descriptors =
+      isolate->factory()->NewJSObject(isolate->object_function());
+
+  for (int i = 0; i < keys->length(); ++i) {
+    Handle<Name> key = Handle<Name>::cast(FixedArray::get(*keys, i, isolate));
+    PropertyDescriptor descriptor;
+    Maybe<bool> did_get_descriptor = JSReceiver::GetOwnPropertyDescriptor(
+        isolate, receiver, key, &descriptor);
+    MAYBE_RETURN(did_get_descriptor, isolate->heap()->exception());
+
+    Handle<Object> from_descriptor = did_get_descriptor.FromJust()

[adamk, 2016/02/04 20:13:48]

Isn't this guaranteed to return true since we MAYBE_RETURN above?

[caitp (gmail), 2016/02/04 20:14:49]

nope, it can return false if the property doesn't exist

+                                         ? descriptor.ToObject(isolate)
+                                         : undefined;
+
+    LookupIterator it = LookupIterator::PropertyOrElement(
+        isolate, descriptors, key, LookupIterator::OWN);
+    Maybe<bool> success = JSReceiver::CreateDataProperty(&it, from_descriptor,
+                                                         Object::DONT_THROW);
+    CHECK(success.FromJust());
+  }
+
+  return *descriptors;
+}
 
 // ES6 section 19.1.2.15 Object.preventExtensions ( O )
 BUILTIN(ObjectPreventExtensions) {
   HandleScope scope(isolate);
   Handle<Object> object = args.atOrUndefined(isolate, 1);
   if (object->IsJSReceiver()) {
     MAYBE_RETURN(JSReceiver::PreventExtensions(Handle<JSReceiver>::cast(object),
                                                Object::THROW_ON_ERROR),
                  isolate->heap()->exception());
   }
@@ skipping 2372 matching lines @@
 BUILTIN_LIST_C(DEFINE_BUILTIN_ACCESSOR_C)
 BUILTIN_LIST_A(DEFINE_BUILTIN_ACCESSOR_A)
 BUILTIN_LIST_H(DEFINE_BUILTIN_ACCESSOR_H)
 BUILTIN_LIST_DEBUG_A(DEFINE_BUILTIN_ACCESSOR_A)
 #undef DEFINE_BUILTIN_ACCESSOR_C
 #undef DEFINE_BUILTIN_ACCESSOR_A
 
 
 }  // namespace internal
 }  // namespace v8