Update ObjectToString to Harmony-draft algorithm

src/api.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/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 3391 matching lines @@
   // Because we use caching to speed up enumeration it is important
   // to never change the result of the basic enumeration function so
   // we clone the result.
   i::Handle<i::FixedArray> elms = isolate->factory()->CopyFixedArray(value);
   i::Handle<i::JSArray> result =
       isolate->factory()->NewJSArrayWithElements(elms);
   return Utils::ToLocal(scope.CloseAndEscape(result));
 }
 
 
+static bool GetPredefinedToString(
+    i::Handle<i::String> tag, Local<String>* result) {
+  i::Isolate* i_isolate = tag->GetIsolate();
+  Isolate* isolate = reinterpret_cast<Isolate*>(i_isolate);
+  i::Factory* factory = i_isolate->factory();
+
+  if (i::String::Equals(tag, factory->Arguments_string())) {
+    *result = v8::String::NewFromUtf8(isolate, "[object ~Arguments]");
+  } else if (i::String::Equals(tag, factory->Array_string())) {
+    *result = v8::String::NewFromUtf8(isolate, "[object ~Array]");
+  } else if (i::String::Equals(tag, factory->Boolean_string())) {
+    *result = v8::String::NewFromUtf8(isolate, "[object ~Boolean]");
+  } else if (i::String::Equals(tag, factory->Date_string())) {
+    *result = v8::String::NewFromUtf8(isolate, "[object ~Date]");
+  } else if (i::String::Equals(tag, factory->Error_string())) {
+    *result = v8::String::NewFromUtf8(isolate, "[object ~Error]");
+  } else if (i::String::Equals(tag, factory->Function_string())) {
+    *result = v8::String::NewFromUtf8(isolate, "[object ~Function]");
+  } else if (i::String::Equals(tag, factory->Number_string())) {
+    *result = v8::String::NewFromUtf8(isolate, "[object ~Number]");
+  } else if (i::String::Equals(tag, factory->RegExp_string())) {
+    *result = v8::String::NewFromUtf8(isolate, "[object ~RegExp]");
+  } else if (i::String::Equals(tag, factory->String_string())) {
+    *result = v8::String::NewFromUtf8(isolate, "[object ~String]");
+  } else {
+    return false;
+  }
+  return true;
+}
+
+
 Local<String> v8::Object::ObjectProtoToString() {
   i::Isolate* i_isolate = Utils::OpenHandle(this)->GetIsolate();
   Isolate* isolate = reinterpret_cast<Isolate*>(i_isolate);
   ON_BAILOUT(i_isolate, "v8::Object::ObjectProtoToString()",
              return Local<v8::String>());
   ENTER_V8(i_isolate);
   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);
   //   if (c === 'Arguments') c  = 'Object';
   //   return "[object " + c + "]";
 
   if (!name->IsString()) {
     return v8::String::NewFromUtf8(isolate, "[object ]");
   } else {
     i::Handle<i::String> class_name = i::Handle<i::String>::cast(name);
     if (i::String::Equals(class_name,
                           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));
+        EXCEPTION_PREAMBLE(i_isolate);
+        has_pending_exception = !i::Runtime::GetObjectProperty(
+            i_isolate, self, toStringTag).ToHandle(&tag);
+        EXCEPTION_BAILOUT_CHECK(i_isolate, Local<v8::String>());
+
+        if (!tag->IsUndefined()) {
+          if (!tag->IsString())
+            return v8::String::NewFromUtf8(isolate, "[object ???]");
+          i::Handle<i::String> tag_name = i::Handle<i::String>::cast(tag);
+          if (!i::String::Equals(class_name, tag_name)) {
+            Local<String> result;
+            if (GetPredefinedToString(tag_name, &result))
+              return result;
+
+            class_name = tag_name;
+          }
+        }
+      }
       const char* prefix = "[object ";
       Local<String> str = Utils::ToLocal(class_name);
       const char* postfix = "]";
 
       int prefix_len = i::StrLength(prefix);
       int str_len = str->Utf8Length();
       int postfix_len = i::StrLength(postfix);
 
       int buf_len = prefix_len + str_len + postfix_len;
       i::ScopedVector<char> buf(buf_len);
@@ skipping 2793 matching lines @@
 Local<Symbol> v8::Symbol::GetIterator(Isolate* isolate) {
   return GetWellKnownSymbol(isolate, "Symbol.iterator");
 }
 
 
 Local<Symbol> v8::Symbol::GetUnscopables(Isolate* isolate) {
   return GetWellKnownSymbol(isolate, "Symbol.unscopables");
 }
 
 
+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()");
   ENTER_V8(i_isolate);
   i::Handle<i::Symbol> symbol = i_isolate->factory()->NewPrivateSymbol();
   if (!name.IsEmpty()) symbol->set_name(*Utils::OpenHandle(*name));
   Local<Symbol> result = Utils::ToLocal(symbol);
   return v8::Handle<Private>(reinterpret_cast<Private*>(*result));
 }
 
@@ skipping 1449 matching lines @@
   Isolate* isolate = reinterpret_cast<Isolate*>(info.GetIsolate());
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 } }  // namespace v8::internal