[runtime] Support Proxy setPrototypeOf trap

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 70cbc484136ad4af6439e2825831ce6574110b67..fc3c6fee4c8df71d7f13e739a54cdfba99c571f7 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -845,15 +845,20 @@ Handle<FixedArray> JSObject::EnsureWritableFastElements(
 }
 
 
-// ES6 9.5.1
+// ES6: Section 9.5.1 [[GetPrototypeOf]] ( )
 // static
 MaybeHandle<Object> JSProxy::GetPrototype(Handle<JSProxy> proxy) {
   Isolate* isolate = proxy->GetIsolate();
+  Handle<Object> trap;
+  Handle<JSReceiver> handle;
+  Handle<Name> trap_name = isolate->factory()->getPrototypeOf_string();
   // 1. Let handler be the value of the [[ProxyHandler]] internal slot.
   Handle<Object> raw_handler(proxy->handler(), isolate);
   // 2. If handler is null, throw a TypeError exception.
   // 3. Assert: Type(handler) is Object.
   if (!raw_handler->IsSpecObject()) {
+    DCHECK(raw_handler->IsNull());
+    DCHECK(proxy->target()->IsNull());
     // TODO(cbruni): Throw correct error message.
     THROW_NEW_ERROR(
         isolate, NewTypeError(MessageTemplate::kProxyHandlerNonObject), Object);
@@ -863,8 +868,6 @@ MaybeHandle<Object> JSProxy::GetPrototype(Handle<JSProxy> proxy) {
   // TODO(cbruni): Change target type to JSReceiver by default.
   Handle<JSReceiver> target(JSReceiver::cast(proxy->target()), isolate);
   // 5. Let trap be ? GetMethod(handler, "getPrototypeOf").
-  Handle<Object> trap;
-  Handle<String> trap_name = isolate->factory()->getPrototypeOf_string();
   ASSIGN_RETURN_ON_EXCEPTION(isolate, trap, GetMethod(handler, trap_name),
                              Object);
   // 6. If trap is undefined, then return target.[[GetPrototypeOf]]().
@@ -879,6 +882,7 @@ MaybeHandle<Object> JSProxy::GetPrototype(Handle<JSProxy> proxy) {
       Execution::Call(isolate, trap, handler, arraysize(argv), argv), Object);
   // 8. If Type(handlerProto) is neither Object nor Null, throw a TypeError.
   if (!(handler_proto->IsSpecObject() || handler_proto->IsNull())) {
+    // TODO(cbruni): throw correct error message
     THROW_NEW_ERROR(isolate,
                     NewTypeError(MessageTemplate::kProxyHandlerTrapMissing,
                                  handler, trap_name),
@@ -905,6 +909,67 @@ MaybeHandle<Object> JSProxy::GetPrototype(Handle<JSProxy> proxy) {
 }
 
 
+// ES6: 9.5.2 [[SetPrototypeOf]] (V)
+// static
+Maybe<bool> JSProxy::SetPrototype(Handle<JSProxy> proxy, Handle<Object> value,
+                                  bool from_javascript,
+                                  Object::ShouldThrow should_throw) {
+  Isolate* isolate = proxy->GetIsolate();
+  Handle<JSReceiver> handle;
+  Handle<Name> trap_name = isolate->factory()->setPrototypeOf_string();
+  // 1. Assert: Either Type(V) is Object or Type(V) is Null.
+  DCHECK(value->IsSpecObject() || value->IsNull());
+  // 2. Let handler be the value of the [[ProxyHandler]] internal slot of O.
+  Handle<Object> raw_handler(proxy->handler(), isolate);
+  // 3. If handler is null, throw a TypeError exception.
+  // 4. Assert: Type(handler) is Object.
+  if (!raw_handler->IsSpecObject()) {
+    DCHECK(raw_handler->IsNull());
+    DCHECK(proxy->target()->IsNull());
+    isolate->Throw(*isolate->factory()->NewTypeError(
+        MessageTemplate::kProxyHandlerNonObject));
+    return Nothing<bool>();
+  }
+  Handle<JSReceiver> handler = Handle<JSReceiver>::cast(raw_handler);
+  // 5. Let target be the value of the [[ProxyTarget]] internal slot.
+  Handle<JSReceiver> target(JSReceiver::cast(proxy->target()), isolate);
+  // 6. Let trap be ? GetMethod(handler, "getPrototypeOf").
+  Handle<Object> trap;
+  ASSIGN_RETURN_ON_EXCEPTION_VALUE(
+      isolate, trap, Object::GetMethod(handler, trap_name), Nothing<bool>());
+  // 7. If trap is undefined, then return target.[[SetPrototypeOf]]().
+  if (trap->IsUndefined()) {
+    return JSReceiver::SetPrototype(target, value, from_javascript,
+                                    should_throw);
+  }
+  // 8. Let booleanTrapResult be ToBoolean(? Call(trap, handler, «target, V»)).
+  Handle<Object> argv[] = {target, value};
+  Handle<Object> trap_result;
+  ASSIGN_RETURN_ON_EXCEPTION_VALUE(
+      isolate, trap_result,
+      Execution::Call(isolate, trap, handler, arraysize(argv), argv),
+      Nothing<bool>());
+  bool bool_trap_result = trap_result->BooleanValue();
+  // 9. Let extensibleTarget be ? IsExtensible(target).
+  Maybe<bool> is_extensible = JSReceiver::IsExtensible(target);
+  if (is_extensible.IsNothing()) return Nothing<bool>();
+  // 10. If extensibleTarget is true, return booleanTrapResult.
+  if (is_extensible.FromJust()) return Just(bool_trap_result);
+  // 11. Let targetProto be ? target.[[GetPrototypeOf]]().
+  Handle<Object> target_proto;
+  ASSIGN_RETURN_ON_EXCEPTION_VALUE(isolate, target_proto,
+                                   Object::GetPrototype(isolate, target),
+                                   Nothing<bool>());
+  // 12. If booleanTrapResult is true and SameValue(V, targetProto) is false,
+  // throw a TypeError exception.
+  if (bool_trap_result && !value->SameValue(*target_proto)) {
+    isolate->Throw(*isolate->factory()->NewTypeError(
+        MessageTemplate::kObjectSetPrototypeNotExtensible));
+  }
+  // 13. Return booleanTrapResult.
+  return Just(bool_trap_result);
+}
+
 MaybeHandle<Object> JSProxy::GetPropertyWithHandler(Handle<JSProxy> proxy,
                                                     Handle<Object> receiver,
                                                     Handle<Name> name) {
@@ -13955,8 +14020,11 @@ Handle<Map> Map::TransitionToPrototype(Handle<Map> map,
 Maybe<bool> JSReceiver::SetPrototype(Handle<JSReceiver> object,
                                      Handle<Object> value, bool from_javascript,
                                      ShouldThrow should_throw) {
-  if (!object->IsJSObject()) return Just(false);
-  // TODO(neis): Deal with proxies.
+  if (!object->IsJSReceiver()) return Just(false);

[neis, 2015/11/16 19:09:53]

What's the motivation for this?

+  if (object->IsJSProxy()) {
+    return JSProxy::SetPrototype(Handle<JSProxy>::cast(object), value,
+                                 from_javascript, should_throw);
+  }
   return JSObject::SetPrototype(Handle<JSObject>::cast(object), value,
                                 from_javascript, should_throw);
 }