Expose well-known Symbols to C++ API.

BUG=341423
LOG=Y
R=arv@chromium.org, dcarney@chromium.org, rossberg@chromium.org

Review URL: https://codereview.chromium.org/483173002

Patch from Yutaka Hirano <yhirano@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23196 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

include/v8.h

@@ -1960,7 +1960,12 @@ class V8_EXPORT Symbol : public Primitive {
   // registry that is not accessible by (and cannot clash with) JavaScript code.
   static Local<Symbol> ForApi(Isolate *isolate, Local<String> name);
 
+  // Well-known symbols
+  static Local<Symbol> GetIterator(Isolate* isolate);
+  static Local<Symbol> GetUnscopables(Isolate* isolate);
+
   V8_INLINE static Symbol* Cast(v8::Value* obj);
+
  private:
   Symbol();
   static void CheckCast(v8::Value* obj);

src/api.cc

@@ -6152,43 +6152,57 @@ Local<Symbol> v8::Symbol::New(Isolate* isolate, Local<String> name) {
 }
 
 
-Local<Symbol> v8::Symbol::For(Isolate* isolate, Local<String> name) {
-  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
-  i::Handle<i::String> i_name = Utils::OpenHandle(*name);
-  i::Handle<i::JSObject> registry = i_isolate->GetSymbolRegistry();
-  i::Handle<i::String> part = i_isolate->factory()->for_string();
+static i::Handle<i::Symbol> SymbolFor(i::Isolate* isolate,
+                                      i::Handle<i::String> name,
+                                      i::Handle<i::String> part) {
+  i::Handle<i::JSObject> registry = isolate->GetSymbolRegistry();
   i::Handle<i::JSObject> symbols =
       i::Handle<i::JSObject>::cast(
           i::Object::GetPropertyOrElement(registry, part).ToHandleChecked());
   i::Handle<i::Object> symbol =
-      i::Object::GetPropertyOrElement(symbols, i_name).ToHandleChecked();
+      i::Object::GetPropertyOrElement(symbols, name).ToHandleChecked();
   if (!symbol->IsSymbol()) {
     DCHECK(symbol->IsUndefined());
-    symbol = i_isolate->factory()->NewSymbol();
-    i::Handle<i::Symbol>::cast(symbol)->set_name(*i_name);
-    i::JSObject::SetProperty(symbols, i_name, symbol, i::STRICT).Assert();
+    symbol = isolate->factory()->NewSymbol();
+    i::Handle<i::Symbol>::cast(symbol)->set_name(*name);
+    i::JSObject::SetProperty(symbols, name, symbol, i::STRICT).Assert();
   }
-  return Utils::ToLocal(i::Handle<i::Symbol>::cast(symbol));
+  return i::Handle<i::Symbol>::cast(symbol);
+}
+
+
+Local<Symbol> v8::Symbol::For(Isolate* isolate, Local<String> name) {
+  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  i::Handle<i::String> i_name = Utils::OpenHandle(*name);
+  i::Handle<i::String> part = i_isolate->factory()->for_string();
+  return Utils::ToLocal(SymbolFor(i_isolate, i_name, part));
 }
 
 
 Local<Symbol> v8::Symbol::ForApi(Isolate* isolate, Local<String> name) {
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
   i::Handle<i::String> i_name = Utils::OpenHandle(*name);
-  i::Handle<i::JSObject> registry = i_isolate->GetSymbolRegistry();
   i::Handle<i::String> part = i_isolate->factory()->for_api_string();
-  i::Handle<i::JSObject> symbols =
-      i::Handle<i::JSObject>::cast(
-          i::Object::GetPropertyOrElement(registry, part).ToHandleChecked());
-  i::Handle<i::Object> symbol =
-      i::Object::GetPropertyOrElement(symbols, i_name).ToHandleChecked();
-  if (!symbol->IsSymbol()) {
-    DCHECK(symbol->IsUndefined());
-    symbol = i_isolate->factory()->NewSymbol();
-    i::Handle<i::Symbol>::cast(symbol)->set_name(*i_name);
-    i::JSObject::SetProperty(symbols, i_name, symbol, i::STRICT).Assert();
-  }
-  return Utils::ToLocal(i::Handle<i::Symbol>::cast(symbol));
+  return Utils::ToLocal(SymbolFor(i_isolate, i_name, part));
+}
+
+
+static Local<Symbol> GetWellKnownSymbol(Isolate* isolate, const char* name) {
+  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  i::Handle<i::String> i_name =
+      Utils::OpenHandle(*String::NewFromUtf8(isolate, name));
+  i::Handle<i::String> part = i_isolate->factory()->for_intern_string();
+  return Utils::ToLocal(SymbolFor(i_isolate, i_name, part));
+}
+
+
+Local<Symbol> v8::Symbol::GetIterator(Isolate* isolate) {
+  return GetWellKnownSymbol(isolate, "Symbol.iterator");
+}
+
+
+Local<Symbol> v8::Symbol::GetUnscopables(Isolate* isolate) {
+  return GetWellKnownSymbol(isolate, "Symbol.unscopables");
 }
 
 

src/heap/heap.h

@@ -294,6 +294,7 @@ namespace internal {
   V(Symbol_string, "Symbol")                                       \
   V(for_string, "for")                                             \
   V(for_api_string, "for_api")                                     \
+  V(for_intern_string, "for_intern")                               \
   V(private_api_string, "private_api")                             \
   V(private_intern_string, "private_intern")                       \
   V(Date_string, "Date")                                           \

test/cctest/test-api.cc

@@ -2924,6 +2924,29 @@ THREADED_TEST(GlobalSymbols) {
 }
 
 
+static void CheckWellKnownSymbol(v8::Local<v8::Symbol>(*getter)(v8::Isolate*),
+                                 const char* name) {
+  LocalContext env;
+  v8::Isolate* isolate = env->GetIsolate();
+  v8::HandleScope scope(isolate);
+
+  v8::Local<v8::Symbol> symbol = getter(isolate);
+  std::string script = std::string("var sym = ") + name;
+  CompileRun(script.c_str());
+  v8::Local<Value> value = env->Global()->Get(v8_str("sym"));
+
+  CHECK(!value.IsEmpty());
+  CHECK(!symbol.IsEmpty());
+  CHECK(value->SameValue(symbol));
+}
+
+
+THREADED_TEST(WellKnownSymbols) {
+  CheckWellKnownSymbol(v8::Symbol::GetIterator, "Symbol.iterator");
+  CheckWellKnownSymbol(v8::Symbol::GetUnscopables, "Symbol.unscopables");
+}
+
+
 THREADED_TEST(GlobalPrivates) {
   LocalContext env;
   v8::Isolate* isolate = env->GetIsolate();