Implement ES6 @@isConcatSpreadable

src/runtime/runtime-array.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/v8.h"
 
 #include "src/arguments.h"
 #include "src/runtime/runtime-utils.h"
 
 namespace v8 {
@@ skipping 422 matching lines @@
     // The prototype will usually have no inherited element indices,
     // but we have to check.
     CollectElementIndices(
         Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter)), range,
         indices);
   }
 }
 
 
 /**
- * A helper function that visits elements of a JSArray in numerical
+ * A helper function that visits elements of a JSObject in numerical
  * order.
  *
  * The visitor argument called for each existing element in the array
  * with the element index and the element's value.
  * Afterwards it increments the base-index of the visitor by the array
  * length.
  * Returns false if any access threw an exception, otherwise true.
  */
-static bool IterateElements(Isolate* isolate, Handle<JSArray> receiver,
+static bool IterateElements(Isolate* isolate, Handle<JSObject> receiver,
                             ArrayConcatVisitor* visitor) {
-  uint32_t length = static_cast<uint32_t>(receiver->length()->Number());
+  uint32_t length = 0;
+
+  if (receiver->IsJSArray()) {
+    Handle<JSArray> array(Handle<JSArray>::cast(receiver));
+    length = static_cast<uint32_t>(array->length()->Number());
+  } else {
+    Handle<Object> val;
+    Handle<Object> key(isolate->heap()->length_string(), isolate);
+    ASSIGN_RETURN_ON_EXCEPTION_VALUE(isolate, val,
+        Runtime::GetObjectProperty(isolate, receiver, key), false);
+    // TODO(caitp): implement ToLength() abstract operation for C++
+    val->ToUint32(&length);
+  }
+
   switch (receiver->GetElementsKind()) {
     case FAST_SMI_ELEMENTS:
     case FAST_ELEMENTS:
     case FAST_HOLEY_SMI_ELEMENTS:
     case FAST_HOLEY_ELEMENTS: {
       // Run through the elements FixedArray and use HasElement and GetElement
       // to check the prototype for missing elements.
       Handle<FixedArray> elements(FixedArray::cast(receiver->elements()));
       int fast_length = static_cast<int>(length);
       DCHECK(fast_length <= elements->length());
@@ skipping 120 matching lines @@
     case EXTERNAL_FLOAT32_ELEMENTS: {
       IterateExternalArrayElements<ExternalFloat32Array, float>(
           isolate, receiver, false, false, visitor);
       break;
     }
     case EXTERNAL_FLOAT64_ELEMENTS: {
       IterateExternalArrayElements<ExternalFloat64Array, double>(
           isolate, receiver, false, false, visitor);
       break;
     }
+    case SLOPPY_ARGUMENTS_ELEMENTS: {
+      ElementsAccessor* accessor = receiver->GetElementsAccessor();
+      for (uint32_t index = 0; index < length; index++) {
+        HandleScope loop_scope(isolate);
+        Handle<Object> element;
+        ASSIGN_RETURN_ON_EXCEPTION_VALUE(
+            isolate, element, accessor->Get(receiver, receiver, index), false);
+        if (!element->IsTheHole()) {

[Dmitry Lomov (no reviews), 2014/12/11 14:01:50]

Use accessor->HasElement(receiver, receiver, index) instead of checking for
hole.

+          visitor->visit(index, element);
+        }
+      }
+      break;
+    }
     default:
       UNREACHABLE();
       break;
   }
   visitor->increase_index_offset(length);
   return true;
 }
 
 
+static bool IsConcatSpreadable(Isolate* isolate, Handle<Object> obj) {
+  HandleScope handle_scope(isolate);
+  if (!obj->IsSpecObject()) return false;
+  if (obj->IsJSArray()) return true;
+  if (FLAG_harmony_arrays) {
+    Handle<Symbol> key(isolate->factory()->is_concat_spreadable_symbol());
+    Handle<Object> value;
+    MaybeHandle<Object> maybeValue =
+        i::Runtime::GetObjectProperty(isolate, obj, key);
+    if (maybeValue.ToHandle(&value)) {
+      return value->BooleanValue();
+    }
+  }
+  return false;
+}
+
+
 /**
  * Array::concat implementation.
  * See ECMAScript 262, 15.4.4.4.
  * TODO(581): Fix non-compliance for very large concatenations and update to
  * following the ECMAScript 5 specification.
  */
 RUNTIME_FUNCTION(Runtime_ArrayConcat) {
   HandleScope handle_scope(isolate);
   DCHECK(args.length() == 1);
 
@@ skipping 150 matching lines @@
     uint32_t at_least_space_for =
         estimate_nof_elements + (estimate_nof_elements >> 2);
     storage = Handle<FixedArray>::cast(
         SeededNumberDictionary::New(isolate, at_least_space_for));
   }
 
   ArrayConcatVisitor visitor(isolate, storage, fast_case);
 
   for (int i = 0; i < argument_count; i++) {
     Handle<Object> obj(elements->get(i), isolate);
-    if (obj->IsJSArray()) {
-      Handle<JSArray> array = Handle<JSArray>::cast(obj);
-      if (!IterateElements(isolate, array, &visitor)) {
+    bool spreadable = IsConcatSpreadable(isolate, obj);
+    if (isolate->has_pending_exception()) return isolate->heap()->exception();
+    if (spreadable) {
+      Handle<JSObject> object = Handle<JSObject>::cast(obj);
+      if (!IterateElements(isolate, object, &visitor)) {
         return isolate->heap()->exception();
       }
     } else {
       visitor.visit(0, obj);
       visitor.increase_index_offset(1);
     }
   }
 
   if (visitor.exceeds_array_limit()) {
     THROW_NEW_ERROR_RETURN_FAILURE(
@@ skipping 400 matching lines @@
 }
 
 
 RUNTIME_FUNCTION(RuntimeReference_FastOneByteArrayJoin) {
   SealHandleScope shs(isolate);
   DCHECK(args.length() == 2);
   return isolate->heap()->undefined_value();
 }
 }
 }  // namespace v8::internal