Gin: Make it easier to implement Wrappable

gin/wrappable_unittest.cc

Index: gin/wrappable_unittest.cc
diff --git a/gin/wrappable_unittest.cc b/gin/wrappable_unittest.cc
index 8886a7990ccebbe7f1950f7577d25a27a039e962..2a5fd44537dd356aab01789fa682f4f6028640e4 100644
--- a/gin/wrappable_unittest.cc
+++ b/gin/wrappable_unittest.cc
@@ -16,16 +16,13 @@
 namespace gin {
 namespace {
 
-class MyObject : public Wrappable {
+class MyObject : public Wrappable<MyObject> {
  public:
   static gin::Handle<MyObject> Create(v8::Isolate* isolate);
 
   int value() const { return value_; }
   void set_value(int value) { value_ = value; }
 
-  static WrapperInfo kWrapperInfo;
-  virtual WrapperInfo* GetWrapperInfo() OVERRIDE;
-
  private:
   MyObject() : value_(0) {}
   virtual ~MyObject() {}
@@ -33,68 +30,46 @@ class MyObject : public Wrappable {
   int value_;
 };
 
-WrapperInfo MyObject::kWrapperInfo = { kEmbedderNativeGin };
-
 gin::Handle<MyObject> MyObject::Create(v8::Isolate* isolate) {
   return CreateHandle(isolate, new MyObject());
 }
 
-WrapperInfo* MyObject::GetWrapperInfo() {
-  return &kWrapperInfo;
-}
-
-
-class MyObject2 : public Wrappable {
- public:
-  MyObject2() {
-  }
-  static WrapperInfo kWrapperInfo;
-  virtual WrapperInfo* GetWrapperInfo() OVERRIDE;
+class MyObject2 : public Wrappable<MyObject2> {
 };
 
-WrapperInfo MyObject2::kWrapperInfo = { kEmbedderNativeGin };
-
-WrapperInfo* MyObject2::GetWrapperInfo() {
-  return &kWrapperInfo;
-}
-
-
-class MyObjectBlink : public Wrappable {
- public:
-  MyObjectBlink() {
-  }
-  static WrapperInfo kWrapperInfo;
-  virtual WrapperInfo* GetWrapperInfo() OVERRIDE;
+class MyObjectBlink : public Wrappable<MyObjectBlink> {
 };
 
-WrapperInfo MyObjectBlink::kWrapperInfo = { kEmbedderBlink };
-
-WrapperInfo* MyObjectBlink::GetWrapperInfo() {
-  return &kWrapperInfo;
-}
-
 
 void RegisterTemplates(v8::Isolate* isolate) {
   PerIsolateData* data = PerIsolateData::From(isolate);
-  DCHECK(data->GetObjectTemplate(&MyObject::kWrapperInfo).IsEmpty());
+  DCHECK(data->GetObjectTemplate(
+      &WrappableTraits<MyObject>::kWrapperInfo).IsEmpty());
 
   v8::Handle<v8::ObjectTemplate> templ = ObjectTemplateBuilder(isolate)
       .SetProperty("value", &MyObject::value, &MyObject::set_value)
       .Build();
   templ->SetInternalFieldCount(kNumberOfInternalFields);
-  data->SetObjectTemplate(&MyObject::kWrapperInfo, templ);
+  data->SetObjectTemplate(&WrappableTraits<MyObject>::kWrapperInfo, templ);
 
   templ = v8::ObjectTemplate::New(isolate);
   templ->SetInternalFieldCount(kNumberOfInternalFields);
-  data->SetObjectTemplate(&MyObject2::kWrapperInfo, templ);
+  data->SetObjectTemplate(&WrappableTraits<MyObject2>::kWrapperInfo, templ);
 
   templ = v8::ObjectTemplate::New(isolate);
   templ->SetInternalFieldCount(kNumberOfInternalFields);
-  data->SetObjectTemplate(&MyObjectBlink::kWrapperInfo, templ);
+  data->SetObjectTemplate(&WrappableTraits<MyObjectBlink>::kWrapperInfo, templ);
 }
 
 typedef V8Test WrappableTest;
 
+TEST_F(WrappableTest, WrappableTraitsAreConstant) {
+  // We rely on the fact that WrappableTraits<T>::kWrapperInfo is constant
+  // across translation units. This test ensures that remains the case.
+  EXPECT_EQ(&WrappableTraits<WrappableTraitsTest>::kWrapperInfo,
+            WrappableTraitsTest::GetWrapperInfo());
+}
+
 TEST_F(WrappableTest, WrapAndUnwrap) {
   v8::Isolate* isolate = instance_->isolate();
   v8::HandleScope handle_scope(isolate);