Add C++ implementation of Object.defineProperties

src/property-descriptor.cc

+// Copyright 2011 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/property-descriptor.h"
+
+#include "src/factory.h"
+#include "src/isolate-inl.h"
+#include "src/lookup.h"
+#include "src/objects-inl.h"
+
+namespace v8 {
+namespace internal {
+
+// Helper function for ToPropertyDescriptor. Comments describe steps for
+// "enumerable", other properties are handled the same way.
+// Returns false if an exception was thrown.
+bool GetPropertyIfPresent(Handle<Object> obj, Handle<String> name,
+                          Handle<Object>* value) {
+  LookupIterator it(obj, name);
+  // 4. Let hasEnumerable be HasProperty(Obj, "enumerable").
+  Maybe<PropertyAttributes> maybe_attr = JSReceiver::GetPropertyAttributes(&it);
+  // 5. ReturnIfAbrupt(hasEnumerable).
+  if (!maybe_attr.IsJust()) return false;
+  // 6. If hasEnumerable is true, then
+  if (maybe_attr.FromJust() != ABSENT) {
+    // 6a. Let enum be ToBoolean(Get(Obj, "enumerable")).
+    // 6b. ReturnIfAbrupt(enum).
+    if (!JSObject::GetProperty(&it).ToHandle(value)) return false;
+  }
+  return true;
+}
+
+
+// Helper function for ToPropertyDescriptor. Handles the case of "simple"
+// objects: nothing on the prototype chain, just own fast data properties.
+// Must not have observable side effects, because the slow path will restart
+// the entire conversion!
+bool ToPropertyDescriptorFastPath(Isolate* isolate, Handle<Object> obj,
+                                  PropertyDescriptor* desc) {
+  if (!obj->IsJSObject()) return false;
+  Map* map = Handle<JSObject>::cast(obj)->map();
+  if (map->instance_type() != JS_OBJECT_TYPE) return false;
+  if (map->is_access_check_needed()) return false;
+  if (map->prototype() != *isolate->initial_object_prototype()) return false;
+  if (JSObject::cast(map->prototype())->map() !=
+      isolate->native_context()->object_function_prototype_map()) {
+    return false;
+  }
+  // TODO(jkummerow): support dictionary properties?
+  if (map->is_dictionary_map()) return false;
+  Handle<DescriptorArray> descs =
+      Handle<DescriptorArray>(map->instance_descriptors());
+  for (int i = 0; i < map->NumberOfOwnDescriptors(); i++) {
+    PropertyDetails details = descs->GetDetails(i);
+    Name* key = descs->GetKey(i);
+    Handle<Object> value;
+    switch (details.type()) {
+      case DATA:
+        value = JSObject::FastPropertyAt(Handle<JSObject>::cast(obj),
+                                         details.representation(),
+                                         FieldIndex::ForDescriptor(map, i));
+        break;
+      case DATA_CONSTANT:
+        value = handle(descs->GetConstant(i), isolate);
+        break;
+      case ACCESSOR:
+      case ACCESSOR_CONSTANT:
+        // Bail out to slow path.
+        return false;
+    }
+    Heap* heap = isolate->heap();
+    if (key == heap->enumerable_string()) {
+      desc->set_enumerable(value->BooleanValue());
+    } else if (key == heap->configurable_string()) {
+      desc->set_configurable(value->BooleanValue());
+    } else if (key == heap->value_string()) {
+      desc->set_value(value);
+    } else if (key == heap->writable_string()) {
+      desc->set_writable(value->BooleanValue());
+    } else if (key == heap->get_string()) {
+      // Bail out to slow path to throw an exception if necessary.
+      if (!value->IsCallable()) return false;
+      desc->set_get(value);
+    } else if (key == heap->set_string()) {
+      // Bail out to slow path to throw an exception if necessary.
+      if (!value->IsCallable()) return false;
+      desc->set_set(value);
+    }
+  }
+  if ((desc->has_get() || desc->has_set()) &&
+      (desc->has_value() || desc->has_writable())) {
+    // Bail out to slow path to throw an exception.
+    return false;
+  }
+  return true;
+}
+
+
+// ES6 6.2.4.5
+// Returns false in case of exception.
+// static
+bool PropertyDescriptor::ToPropertyDescriptor(Isolate* isolate,
+                                              Handle<Object> obj,
+                                              PropertyDescriptor* desc) {
+  // 1. ReturnIfAbrupt(Obj).
+  // 2. If Type(Obj) is not Object, throw a TypeError exception.
+  if (!obj->IsSpecObject()) {
+    isolate->Throw(*isolate->factory()->NewTypeError(
+        MessageTemplate::kPropertyDescObject, obj));
+    return false;
+  }
+  // 3. Let desc be a new Property Descriptor that initially has no fields.
+  DCHECK(desc->is_empty());
+
+  if (ToPropertyDescriptorFastPath(isolate, obj, desc)) {
+    return true;
+  }
+
+  // TODO(jkummerow): Implement JSProxy support.
+  if (!obj->IsJSProxy()) {

[Toon Verwaest, 2015/10/06 15:55:18]

I don't think this is good enough. GetPropertyIfPresent, as the spec requires,
just does HasProperty and Get, which will fetch through the prototype chain.
That will still call into proxy handlers if there's a proxy on the prototype
chain. Actually GetPropertyAttributes will result in the wrong trap being
triggered, and this particular check won't prevent that from happening.

[Jakob Kummerow, 2015/10/09 13:46:12]

Acknowledged. I'd prefer to do this in a follow-up CL; I've expanded the TODO
comment to include more detail.

+    {  // enumerable?
+      Handle<Object> enumerable;
+      // 4 through 6b.
+      if (!GetPropertyIfPresent(obj, isolate->factory()->enumerable_string(),
+                                &enumerable)) {
+        return false;
+      }
+      // 6c. Set the [[Enumerable]] field of desc to enum.
+      if (!enumerable.is_null()) {
+        desc->set_enumerable(enumerable->BooleanValue());
+      }
+    }
+    {  // configurable?
+      Handle<Object> configurable;
+      // 7 through 9b.
+      if (!GetPropertyIfPresent(obj, isolate->factory()->configurable_string(),
+                                &configurable)) {
+        return false;
+      }
+      // 9c. Set the [[Configurable]] field of desc to conf.
+      if (!configurable.is_null()) {
+        desc->set_configurable(configurable->BooleanValue());
+      }
+    }
+    {  // value?
+      Handle<Object> value;
+      // 10 through 12b.
+      if (!GetPropertyIfPresent(obj, isolate->factory()->value_string(),
+                                &value))
+        return false;
+      // 12c. Set the [[Value]] field of desc to value.
+      if (!value.is_null()) desc->set_value(value);
+    }
+    {  // writable?
+      Handle<Object> writable;
+      // 13 through 15b.
+      if (!GetPropertyIfPresent(obj, isolate->factory()->writable_string(),
+                                &writable)) {
+        return false;
+      }
+      // 15c. Set the [[Writable]] field of desc to writable.
+      if (!writable.is_null()) desc->set_writable(writable->BooleanValue());
+    }
+    {  // getter?
+      Handle<Object> getter;
+      // 16 through 18b.
+      if (!GetPropertyIfPresent(obj, isolate->factory()->get_string(), &getter))
+        return false;
+      if (!getter.is_null()) {
+        // 18c. If IsCallable(getter) is false and getter is not undefined,
+        // throw a TypeError exception.
+        if (!getter->IsCallable() && !getter->IsUndefined()) {
+          isolate->Throw(*isolate->factory()->NewTypeError(
+              MessageTemplate::kObjectGetterCallable, getter));
+          return false;
+        }
+        // 18d. Set the [[Get]] field of desc to getter.
+        desc->set_get(getter);
+      }
+      {  // setter?
+        Handle<Object> setter;
+        // 19 through 21b.
+        if (!GetPropertyIfPresent(obj, isolate->factory()->set_string(),
+                                  &setter))
+          return false;
+        if (!setter.is_null()) {
+          // 21c. If IsCallable(setter) is false and setter is not undefined,
+          // throw a TypeError exception.
+          if (!setter->IsCallable() && !setter->IsUndefined()) {
+            isolate->Throw(*isolate->factory()->NewTypeError(
+                MessageTemplate::kObjectSetterCallable, setter));
+            return false;
+          }
+          // 21d. Set the [[Set]] field of desc to setter.
+          desc->set_set(setter);
+        }
+      }
+      // 22. If either desc.[[Get]] or desc.[[Set]] is present, then
+      // 22a. If either desc.[[Value]] or desc.[[Writable]] is present,
+      // throw a TypeError exception.
+      if ((desc->has_get() || desc->has_set()) &&
+          (desc->has_value() || desc->has_writable())) {
+        isolate->Throw(*isolate->factory()->NewTypeError(
+            MessageTemplate::kValueAndAccessor, obj));
+        return false;
+      }
+    }
+  } else {
+    DCHECK(obj->IsJSProxy());
+    UNIMPLEMENTED();
+  }
+  // 23. Return desc.
+  return true;
+}
+
+
+}  // namespace internal
+}  // namespace v8