[proxies] Make Array.isArray respect proxies.

An array is either a JSArray or a proxy whose target is an array.

R=bmeurer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1497483004

Cr-Commit-Position: refs/heads/master@{#32558}

src/bootstrapper.cc

@@ -1014,6 +1014,20 @@ void Genesis::HookUpGlobalObject(Handle<JSGlobalObject> global_object) {
 }
 
 
+static void SimpleInstallFunction(Handle<JSObject> base, Handle<Name> name,
+                                  Builtins::Name call, int len, bool adapt) {
+  Handle<JSFunction> fun =
+      InstallFunction(base, name, JS_OBJECT_TYPE, JSObject::kHeaderSize,
+                      MaybeHandle<JSObject>(), call, DONT_ENUM);
+  if (adapt) {
+    fun->shared()->set_internal_formal_parameter_count(len);
+  } else {
+    fun->shared()->DontAdaptArguments();
+  }
+  fun->shared()->set_length(len);
+}
+
+
 // This is only called if we are not using snapshots.  The equivalent
 // work in the snapshot case is done in HookUpGlobalObject.
 void Genesis::InitializeGlobal(Handle<JSGlobalObject> global_object,
@@ -1100,6 +1114,10 @@ void Genesis::InitializeGlobal(Handle<JSGlobalObject> global_object,
         Map::Copy(initial_map, "SetInstancePrototype");
     initial_strong_map->set_is_strong();
     CacheInitialJSArrayMaps(native_context(), initial_strong_map);
+
+    SimpleInstallFunction(array_function,
+        factory->NewStringFromAsciiChecked("isArray"),
+        Builtins::kArrayIsArray, 1, true);
   }
 
   {  // --- N u m b e r ---
@@ -1969,20 +1987,6 @@ EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_do_expressions)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_regexp_lookbehind)
 
 
-static void SimpleInstallFunction(Handle<JSObject> base, Handle<Name> name,
-                                  Builtins::Name call, int len, bool adapt) {
-  Handle<JSFunction> fun =
-      InstallFunction(base, name, JS_OBJECT_TYPE, JSObject::kHeaderSize,
-                      MaybeHandle<JSObject>(), call, DONT_ENUM);
-  if (adapt) {
-    fun->shared()->set_internal_formal_parameter_count(len);
-  } else {
-    fun->shared()->DontAdaptArguments();
-  }
-  fun->shared()->set_length(len);
-}
-
-
 void InstallPublicSymbol(Factory* factory, Handle<Context> native_context,
                          const char* name, Handle<Symbol> value) {
   Handle<JSGlobalObject> global(

src/builtins.cc

@@ -1423,6 +1423,17 @@ BUILTIN(ArrayConcat) {
 }
 
 
+// ES6 section 22.1.2.2 Array.isArray
+BUILTIN(ArrayIsArray) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(2, args.length());
+  Handle<Object> object = args.at<Object>(1);
+  Maybe<bool> result = Object::IsArray(object);
+  MAYBE_RETURN(result, isolate->heap()->exception());
+  return *isolate->factory()->ToBoolean(result.FromJust());
+}
+
+
 // ES6 section 26.1.3 Reflect.defineProperty
 BUILTIN(ReflectDefineProperty) {
   HandleScope scope(isolate);

src/builtins.h

@@ -56,13 +56,14 @@ inline bool operator&(BuiltinExtraArguments lhs, BuiltinExtraArguments rhs) {
                                                 \
   V(EmptyFunction, kNone)                       \
                                                 \
-  V(ArrayPush, kNone)                           \
+  V(ArrayConcat, kNone)                         \
+  V(ArrayIsArray, kNone)                        \
   V(ArrayPop, kNone)                            \
+  V(ArrayPush, kNone)                           \
   V(ArrayShift, kNone)                          \
-  V(ArrayUnshift, kNone)                        \
   V(ArraySlice, kNone)                          \
   V(ArraySplice, kNone)                         \
-  V(ArrayConcat, kNone)                         \
+  V(ArrayUnshift, kNone)                        \
                                                 \
   V(DateToPrimitive, kNone)                     \
                                                 \

src/js/array.js

@@ -1697,12 +1697,6 @@ function ArrayFill(value, start, end) {
 }
 
 
-// ES5, 15.4.3.2
-function ArrayIsArray(obj) {
-  return IS_ARRAY(obj);
-}
-
-
 function AddArrayElement(constructor, array, i, value) {
   if (constructor === GlobalArray) {
     AddIndexedProperty(array, i, value);
@@ -1816,7 +1810,6 @@ var unscopables = {
 
 // Set up non-enumerable functions on the Array object.
 utils.InstallFunctions(GlobalArray, DONT_ENUM, [
-  "isArray", ArrayIsArray,
   "from", ArrayFrom,
   "of", ArrayOf
 ]);

src/objects.cc

@@ -624,6 +624,23 @@ MaybeHandle<Object> Object::BitwiseXor(Isolate* isolate, Handle<Object> lhs,
 }
 
 
+Maybe<bool> Object::IsArray(Handle<Object> object) {
+  if (object->IsJSArray()) return Just(true);
+  if (object->IsJSProxy()) {
+    Handle<JSProxy> proxy = Handle<JSProxy>::cast(object);
+    Isolate* isolate = proxy->GetIsolate();
+    if (proxy->IsRevoked()) {
+      isolate->Throw(*isolate->factory()->NewTypeError(
+          MessageTemplate::kProxyRevoked,
+          isolate->factory()->NewStringFromAsciiChecked("IsArray")));
+      return Nothing<bool>();
+    }
+    return Object::IsArray(handle(proxy->target(), isolate));
+  }
+  return Just(false);
+}
+
+
 bool Object::IsPromise(Handle<Object> object) {
   if (!object->IsJSObject()) return false;
   auto js_object = Handle<JSObject>::cast(object);
@@ -996,7 +1013,7 @@ MaybeHandle<Object> JSProxy::GetPrototype(Handle<JSProxy> proxy) {
 }
 
 
-bool JSProxy::IsRevoked() {
+bool JSProxy::IsRevoked() const {
   // TODO(neis): Decide on how to represent revocation.  For now, revocation is
   // unsupported.
   DCHECK(target()->IsJSReceiver());

src/objects.h

@@ -1055,6 +1055,9 @@ class Object {
   STRUCT_LIST(DECLARE_STRUCT_PREDICATE)
 #undef DECLARE_STRUCT_PREDICATE
 
+  // ES6, section 7.2.2 IsArray.  NOT to be confused with %_IsArray.
+  MUST_USE_RESULT static Maybe<bool> IsArray(Handle<Object> object);
+
   // ES6, section 7.2.3 IsCallable.
   INLINE(bool IsCallable() const);
 
@@ -9498,7 +9501,7 @@ class JSProxy: public JSReceiver {
 
   DECLARE_CAST(JSProxy)
 
-  bool IsRevoked();
+  bool IsRevoked() const;
 
   // ES6 9.5.1
   static MaybeHandle<Object> GetPrototype(Handle<JSProxy> receiver);

test/mjsunit/array-isarray.js

+// Copyright 2015 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.
+
+// Flags: --harmony-proxies
+
+
+assertTrue(Array.isArray([]));
+assertFalse(Array.isArray({}));
+assertFalse(Array.isArray(null));
+
+assertTrue(Array.isArray(new Proxy([], {})));
+assertFalse(Array.isArray(new Proxy({}, {})));
+
+assertTrue(Array.isArray(new Proxy(new Proxy([], {}), {})));
+assertFalse(Array.isArray(new Proxy(new Proxy({}, {}), {})));