[ESnext] Implement Object Rest

src/runtime/runtime-object.cc

 // Copyright 2014 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/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/bootstrapper.h"
 #include "src/debug/debug.h"
 #include "src/isolate-inl.h"
@@ skipping 728 matching lines @@
 
   RETURN_FAILURE_ON_EXCEPTION(
       isolate,
       JSObject::DefineAccessor(object, name, getter,
                                isolate->factory()->null_value(), attrs));
   return isolate->heap()->undefined_value();
 }
 
 RUNTIME_FUNCTION(Runtime_CopyDataProperties) {
   HandleScope scope(isolate);
-  DCHECK(args.length() == 2);
+  DCHECK_EQ(2, args.length());
   CONVERT_ARG_HANDLE_CHECKED(JSObject, target, 0);
   CONVERT_ARG_HANDLE_CHECKED(Object, source, 1);
 
   // 2. If source is undefined or null, let keys be an empty List.
   if (source->IsUndefined(isolate) || source->IsNull(isolate)) {
     return isolate->heap()->undefined_value();
   }
 
-  MAYBE_RETURN(
-      JSReceiver::SetOrCopyDataProperties(isolate, target, source, false),
-      isolate->heap()->exception());
+  MAYBE_RETURN(JSReceiver::SetOrCopyDataProperties(isolate, target, source,
+                                                   nullptr, false),
+               isolate->heap()->exception());
   return isolate->heap()->undefined_value();
 }
 
+RUNTIME_FUNCTION(Runtime_CopyDataPropertiesWithExcludedProperties) {

[Dan Ehrenberg, 2017/01/17 23:53:14]

Unimportant to answer before this lands: I've been seeing other code go in where
the parser outputs code to call a builtin function which is on the context,
rather than a runtime function. That could be done here too. What's the general
best practice?

[gsathya, 2017/01/18 00:58:21]

Not sure about what's more performant, tbh. I went with this approach because
there's no need to create a js function for this or expose it to userland js.
builtins *only* installed on the context are an exception and seem to be mostly
used when there's existing codestubs that can be reused from within the builtin 

+  HandleScope scope(isolate);
+  DCHECK_LE(1, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(Object, source, 0);
+
+  // 2. If source is undefined or null, let keys be an empty List.
+  if (source->IsUndefined(isolate) || source->IsNull(isolate)) {
+    return isolate->heap()->undefined_value();
+  }
+
+  ScopedVector<Handle<Name>> excluded_properties(args.length() - 1);
+  for (int i = 1; i < args.length(); i++) {
+    excluded_properties[i - 1] = args.at<Name>(i);
+  }
+
+  Handle<JSObject> target =
+      isolate->factory()->NewJSObject(isolate->object_function());
+  MAYBE_RETURN(JSReceiver::SetOrCopyDataProperties(isolate, target, source,
+                                                   &excluded_properties, false),
+               isolate->heap()->exception());
+  return *target;
+}
+
 RUNTIME_FUNCTION(Runtime_DefineSetterPropertyUnchecked) {
   HandleScope scope(isolate);
   DCHECK_EQ(4, args.length());
   CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
   CONVERT_ARG_HANDLE_CHECKED(Name, name, 1);
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, setter, 2);
   CONVERT_PROPERTY_ATTRIBUTES_CHECKED(attrs, 3);
 
   if (String::cast(setter->shared()->name())->length() == 0) {
     JSFunction::SetName(setter, name, isolate->factory()->set_string());
@@ skipping 167 matching lines @@
   if (!success) return isolate->heap()->exception();
   MAYBE_RETURN(
       JSReceiver::CreateDataProperty(&it, value, Object::THROW_ON_ERROR),
       isolate->heap()->exception());
   return *value;
 }
 
 
 }  // namespace internal
 }  // namespace v8