[es6] Partially implement Reflect.getOwnPropertyDescriptor.

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"
 #include "src/bootstrapper.h"
 #include "src/elements.h"
 #include "src/frames-inl.h"
 #include "src/gdb-jit.h"
 #include "src/ic/handler-compiler.h"
 #include "src/ic/ic.h"
 #include "src/isolate-inl.h"
 #include "src/messages.h"
 #include "src/profiler/cpu-profiler.h"
+#include "src/property-descriptor.h"
 #include "src/prototype.h"
 #include "src/vm-state-inl.h"
 
 namespace v8 {
 namespace internal {
 
 namespace {
 
 // Arguments object passed to C++ builtins.
 template <BuiltinExtraArguments extra_args>
@@ skipping 1462 matching lines @@
 
   Handle<Object> result;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, result, Object::GetPropertyOrElement(
           Handle<JSReceiver>::cast(target), name, receiver));
 
   return *result;
 }
 
 
+// ES6 section 26.1.7 Reflect.getOwnPropertyDescriptor
+BUILTIN(ReflectGetOwnPropertyDescriptor) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(3, args.length());
+  Handle<Object> target = args.at<Object>(1);
+  Handle<Object> key = args.at<Object>(2);
+
+  if (!target->IsJSReceiver()) {
+    THROW_NEW_ERROR_RETURN_FAILURE(
+        isolate, NewTypeError(MessageTemplate::kCalledOnNonObject,
+                              isolate->factory()->NewStringFromAsciiChecked(
+                                  "Reflect.getOwnPropertyDescriptor")));
+  }
+
+  Handle<Name> name;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, name,
+                                     Object::ToName(isolate, key));
+
+  PropertyDescriptor desc;
+  bool found = JSReceiver::GetOwnPropertyDescriptor(
+      isolate, Handle<JSReceiver>::cast(target), name, &desc);
+  if (isolate->has_pending_exception()) return isolate->heap()->exception();
+  if (!found) return isolate->heap()->undefined_value();

[Jakob Kummerow, 2015/10/26 13:58:26]

How about folding this into PropertyDescriptor::ToObject? It would nicely mirror
step 1 "If Desc is undefined, return undefined." of the spec if that function
began with "if (this->IsEmpty()) return isolate->heap()->undefined_value();".

[neis, 2015/10/29 16:48:39]

This doesn't quite work without passing in "found" to ToObject (I don't want to
treat the empty descriptor as undefined).

Related to that, I changed ToObject slightly such that it works even for
incomplete descriptors.  There was no good reason for assuming complete inputs
(it only saved a few checks).  Please have another look.

+  return *desc.ToObject(isolate);
+}
+
+
 // ES6 section 26.1.8 Reflect.getPrototypeOf
 BUILTIN(ReflectGetPrototypeOf) {
   HandleScope scope(isolate);
   DCHECK_EQ(2, args.length());
   Handle<Object> target = args.at<Object>(1);
 
   if (!target->IsJSReceiver()) {
     THROW_NEW_ERROR_RETURN_FAILURE(
         isolate, NewTypeError(MessageTemplate::kCalledOnNonObject,
                               isolate->factory()->NewStringFromAsciiChecked(
@@ skipping 753 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