Update ObjectToString to Harmony-draft algorithm

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 0c78b5f27058f923fc02ccd2b9b6dc6e53c8bca7..a0286cefc68bac78baac63c6219440d6e56d9b57 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -3379,6 +3379,7 @@ Local<String> v8::Object::ObjectProtoToString() {
   i::Handle<i::JSObject> self = Utils::OpenHandle(this);
 
   i::Handle<i::Object> name(self->class_name(), i_isolate);
+  i::Handle<i::Object> tag;
 
   // Native implementation of Object.prototype.toString (v8natives.js):
   //   var c = %_ClassOf(this);
@@ -3393,6 +3394,53 @@ Local<String> v8::Object::ObjectProtoToString() {
                           i_isolate->factory()->Arguments_string())) {
       return v8::String::NewFromUtf8(isolate, "[object Object]");
     } else {
+      if (internal::FLAG_harmony_tostring) {
+        i::Handle<i::Symbol> toStringTag = Utils::OpenHandle(
+            *Symbol::GetToStringTag(isolate));
+        tag = i::Runtime::GetObjectProperty(

[Dmitry Lomov (no reviews), 2014/10/18 15:16:48]

This calls into Javascript, so needs EXCEPTION_PREAMBLE/EXCEPTION_BAILOUT_CHECK.
(also add a test for for JS object that throws in toString handle. The code as
you wrote it will just crash if that happens)

+            i_isolate, self, toStringTag).ToHandleChecked();
+
+        if (!tag->IsUndefined()) {
+          if (!tag->IsString()) {
+            return v8::String::NewFromUtf8(isolate, "[object ???]");
+          } else {
+            i::Handle<i::String> tag_name = i::Handle<i::String>::cast(tag);
+            using namespace internal;

[Dmitry Lomov (no reviews), 2014/10/18 15:16:48]

Nit: remove 'using namespace internal' here, we use i:: prefix everywhere.
Suggestion: extract all this tag checking logic into a helper function:
  bool GetPredefinedToString(Handle<String>* result)

+            if (!i::String::Equals(class_name, tag_name)) {
+              if (i::String::Equals(
+                  tag_name, i_isolate->factory()->Arguments_string())) {

[Dmitry Lomov (no reviews), 2014/10/18 15:16:48]

Nit: introduce variable for i_isolate->factory()

+                return v8::String::NewFromUtf8(isolate, "[object ~Arguments]");
+              } else if (i::String::Equals(
+                  tag_name, i_isolate->factory()->Array_string())) {
+                return v8::String::NewFromUtf8(isolate, "[object ~Array]");
+              } else if (i::String::Equals(
+                  tag_name, i_isolate->factory()->Boolean_string())) {
+                return v8::String::NewFromUtf8(isolate, "[object ~Boolean]");
+              } else if (i::String::Equals(
+                  tag_name, i_isolate->factory()->Date_string())) {
+                return v8::String::NewFromUtf8(isolate, "[object ~Date]");
+              } else if (i::String::Equals(
+                  tag_name, i_isolate->factory()->Error_string())) {
+                return v8::String::NewFromUtf8(isolate, "[object ~Error]");
+              } else if (i::String::Equals(
+                  tag_name, i_isolate->factory()->Function_string())) {
+                return v8::String::NewFromUtf8(isolate, "[object ~Function]");
+              } else if (i::String::Equals(
+                  tag_name, i_isolate->factory()->Number_string())) {
+                return v8::String::NewFromUtf8(isolate, "[object ~Number]");
+              } else if (i::String::Equals(
+                  tag_name, i_isolate->factory()->RegExp_string())) {
+                return v8::String::NewFromUtf8(isolate, "[object ~RegExp]");
+              } else if (i::String::Equals(
+                  tag_name, i_isolate->factory()->String_string())) {
+                return v8::String::NewFromUtf8(isolate, "[object ~String]");
+              } else {
+                class_name = tag_name;
+              }
+            }
+          }
+        }
+      }
       const char* prefix = "[object ";
       Local<String> str = Utils::ToLocal(class_name);
       const char* postfix = "]";
@@ -6199,6 +6247,11 @@ Local<Symbol> v8::Symbol::GetUnscopables(Isolate* isolate) {
 }
 
 
+Local<Symbol> v8::Symbol::GetToStringTag(Isolate* isolate) {
+  return GetWellKnownSymbol(isolate, "Symbol.toStringTag");
+}
+
+
 Local<Private> v8::Private::New(Isolate* isolate, Local<String> name) {
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
   LOG_API(i_isolate, "Private::New()");