This implements unscopables

The unscobables allow us to black list properties from showing up in
with statements.

https://people.mozilla.org/~jorendorff/es6-draft.html#sec-object-environment-records-hasbinding-n

The spec draft is not fully up to date.

https://github.com/rwaldron/tc39-notes/blob/master/es6/2014-07/jul-29.md#conclusionresolution

BUG=v8:3401
LOG=Y
R=rossberg@chromium.org, verwaest@chromium.org

Review URL: https://codereview.chromium.org/384963002

Patch from Erik Arvidsson <arv@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22942 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

BUILD.gn

@@ -253,6 +253,7 @@ action("js2c_experimental") {
     "src/array-iterator.js",
     "src/harmony-string.js",
     "src/harmony-array.js",
+    "src/unscopables.js",
   ]
 
   outputs = [

src/bootstrapper.cc

@@ -1625,6 +1625,10 @@ void Genesis::InstallExperimentalNativeFunctions() {
     INSTALL_NATIVE(JSFunction, "DerivedSetTrap", derived_set_trap);
     INSTALL_NATIVE(JSFunction, "ProxyEnumerate", proxy_enumerate);
   }
+
+  if (FLAG_harmony_unscopables) {
+    INSTALL_NATIVE(Symbol, "symbolUnscopables", unscopables_symbol);
+  }
 }
 
 #undef INSTALL_NATIVE
@@ -2063,6 +2067,7 @@ bool Genesis::InstallExperimentalNatives() {
     INSTALL_EXPERIMENTAL_NATIVE(i, iteration, "string-iterator.js")
     INSTALL_EXPERIMENTAL_NATIVE(i, strings, "harmony-string.js")
     INSTALL_EXPERIMENTAL_NATIVE(i, arrays, "harmony-array.js")
+    INSTALL_EXPERIMENTAL_NATIVE(i, unscopables, "unscopables.js")
   }
 
   InstallExperimentalNativeFunctions();

src/contexts.cc

@@ -71,6 +71,38 @@ void Context::set_global_proxy(JSObject* object) {
 }
 
 
+/**
+ * Lookups a property in an object environment, taking the unscopables into
+ * account. This is used For HasBinding spec algorithms for ObjectEnvironment.
+ */
+static Maybe<PropertyAttributes> UnscopableLookup(LookupIterator* it) {
+  Isolate* isolate = it->isolate();
+
+  Maybe<PropertyAttributes> attrs = JSReceiver::GetPropertyAttributes(it);
+  DCHECK(attrs.has_value || isolate->has_pending_exception());
+  if (!attrs.has_value || attrs.value == ABSENT) return attrs;
+
+  Handle<Symbol> unscopables_symbol(
+      isolate->native_context()->unscopables_symbol(), isolate);
+  Handle<Object> receiver = it->GetReceiver();
+  Handle<Object> unscopables;
+  MaybeHandle<Object> maybe_unscopables =
+      Object::GetProperty(receiver, unscopables_symbol);
+  if (!maybe_unscopables.ToHandle(&unscopables)) {
+    return Maybe<PropertyAttributes>();
+  }
+  if (!unscopables->IsSpecObject()) return attrs;
+  Maybe<bool> blacklist = JSReceiver::HasProperty(
+      Handle<JSReceiver>::cast(unscopables), it->name());
+  if (!blacklist.has_value) {
+    DCHECK(isolate->has_pending_exception());
+    return Maybe<PropertyAttributes>();
+  }
+  if (blacklist.value) return maybe(ABSENT);
+  return attrs;
+}
+
+
 Handle<Object> Context::Lookup(Handle<String> name,
                                ContextLookupFlags flags,
                                int* index,
@@ -110,9 +142,13 @@ Handle<Object> Context::Lookup(Handle<String> name,
       if ((flags & FOLLOW_PROTOTYPE_CHAIN) == 0 ||
           object->IsJSContextExtensionObject()) {
         maybe = JSReceiver::GetOwnPropertyAttributes(object, name);
+      } else if (FLAG_harmony_unscopables && context->IsWithContext()) {
+        LookupIterator it(object, name);
+        maybe = UnscopableLookup(&it);
       } else {
         maybe = JSReceiver::GetPropertyAttributes(object, name);
       }
+
       if (!maybe.has_value) return Handle<Object>();
       DCHECK(!isolate->has_pending_exception());
       *attributes = maybe.value;

src/contexts.h

@@ -200,7 +200,8 @@ enum BindingFlags {
   V(ITERATOR_RESULT_MAP_INDEX, Map, iterator_result_map)                       \
   V(MAP_ITERATOR_MAP_INDEX, Map, map_iterator_map)                             \
   V(SET_ITERATOR_MAP_INDEX, Map, set_iterator_map)                             \
-  V(ITERATOR_SYMBOL_INDEX, Symbol, iterator_symbol)
+  V(ITERATOR_SYMBOL_INDEX, Symbol, iterator_symbol)                            \
+  V(UNSCOPABLES_SYMBOL_INDEX, Symbol, unscopables_symbol)
 
 // JSFunctions are pairs (context, function code), sometimes also called
 // closures. A Context object is used to represent function contexts and
@@ -394,6 +395,7 @@ class Context: public FixedArray {
     MAP_ITERATOR_MAP_INDEX,
     SET_ITERATOR_MAP_INDEX,
     ITERATOR_SYMBOL_INDEX,
+    UNSCOPABLES_SYMBOL_INDEX,
 
     // Properties from here are treated as weak references by the full GC.
     // Scavenge treats them as strong references.

src/flag-definitions.h

@@ -161,6 +161,7 @@ DEFINE_BOOL(harmony_numeric_literals, false,
 DEFINE_BOOL(harmony_strings, false, "enable harmony string")
 DEFINE_BOOL(harmony_arrays, false, "enable harmony arrays")
 DEFINE_BOOL(harmony_arrow_functions, false, "enable harmony arrow functions")
+DEFINE_BOOL(harmony_unscopables, false, "enable harmony unscopables")
 DEFINE_BOOL(harmony, false, "enable all harmony features")
 
 DEFINE_IMPLICATION(harmony, harmony_scoping)

src/symbol.js

@@ -105,7 +105,7 @@ function SetUpSymbol() {
     // "isRegExp", symbolIsRegExp,
     "iterator", symbolIterator
     // "toStringTag", symbolToStringTag,
-    // "unscopables", symbolUnscopables
+    // "unscopables", symbolUnscopables  // added in unscopables.js
   ));
   InstallFunctions($Symbol, DONT_ENUM, $Array(
     "for", SymbolFor,

src/unscopables.js

+// 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.
+
+'use strict';
+
+// This file relies on the fact that the following declaration has been made.
+// var $Array = global.Array;
+// var $Symbol = global.Symbol;
+
+function ExtendSymbol() {
+  %CheckIsBootstrapping();
+  InstallConstants($Symbol, $Array(
+    "unscopables", symbolUnscopables
+  ));
+}
+
+ExtendSymbol();
+
+
+var arrayUnscopables = {
+  __proto__: null,
+  copyWithin: true,
+  entries: true,
+  fill: true,
+  find: true,
+  findIndex: true,
+  keys: true,
+  values: true,
+};
+
+
+function ExtendArrayPrototype() {
+  %CheckIsBootstrapping();
+  %AddNamedProperty($Array.prototype, symbolUnscopables, arrayUnscopables,
+                    DONT_ENUM | READ_ONLY);
+}
+
+ExtendArrayPrototype();

test/cctest/cctest.gyp

@@ -156,6 +156,7 @@
         'test-types.cc',
         'test-unbound-queue.cc',
         'test-unique.cc',
+        'test-unscopables-hidden-prototype.cc',
         'test-utils.cc',
         'test-version.cc',
         'test-weakmaps.cc',

test/cctest/test-unscopables-hidden-prototype.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 <stdlib.h>
+
+#include "src/v8.h"
+#include "test/cctest/cctest.h"
+
+namespace {
+
+
+static void Cleanup() {
+  CompileRun(
+      "delete object.x;"
+      "delete hidden_prototype.x;"
+      "delete object[Symbol.unscopables];"
+      "delete hidden_prototype[Symbol.unscopables];");
+}
+
+
+TEST(Unscopables) {
+  i::FLAG_harmony_unscopables = true;
+
+  LocalContext context;
+  v8::Isolate* isolate = context->GetIsolate();
+  v8::HandleScope handle_scope(isolate);
+
+  v8::Local<v8::FunctionTemplate> t0 = v8::FunctionTemplate::New(isolate);
+  v8::Local<v8::FunctionTemplate> t1 = v8::FunctionTemplate::New(isolate);
+
+  t1->SetHiddenPrototype(true);
+
+  v8::Local<v8::Object> object = t0->GetFunction()->NewInstance();
+  v8::Local<v8::Object> hidden_prototype = t1->GetFunction()->NewInstance();
+
+  object->SetPrototype(hidden_prototype);
+
+  context->Global()->Set(v8_str("object"), object);
+  context->Global()->Set(v8_str("hidden_prototype"), hidden_prototype);
+
+  CHECK_EQ(1, CompileRun(
+                  "var result;"
+                  "var x = 0;"
+                  "object.x = 1;"
+                  "with (object) {"
+                  "  result = x;"
+                  "}"
+                  "result")->Int32Value());
+
+  Cleanup();
+  CHECK_EQ(2, CompileRun(
+                  "var result;"
+                  "var x = 0;"
+                  "hidden_prototype.x = 2;"
+                  "with (object) {"
+                  "  result = x;"
+                  "}"
+                  "result")->Int32Value());
+
+  Cleanup();
+  CHECK_EQ(0, CompileRun(
+                  "var result;"
+                  "var x = 0;"
+                  "object.x = 3;"
+                  "object[Symbol.unscopables] = {x: true};"
+                  "with (object) {"
+                  "  result = x;"
+                  "}"
+                  "result")->Int32Value());
+
+  Cleanup();
+  CHECK_EQ(0, CompileRun(
+                  "var result;"
+                  "var x = 0;"
+                  "hidden_prototype.x = 4;"
+                  "hidden_prototype[Symbol.unscopables] = {x: true};"
+                  "with (object) {"
+                  "  result = x;"
+                  "}"
+                  "result")->Int32Value());
+
+  Cleanup();
+  CHECK_EQ(0, CompileRun(
+                  "var result;"
+                  "var x = 0;"
+                  "object.x = 5;"
+                  "hidden_prototype[Symbol.unscopables] = {x: true};"
+                  "with (object) {"
+                  "  result = x;"
+                  "}"
+                  "result;")->Int32Value());
+
+  Cleanup();
+  CHECK_EQ(0, CompileRun(
+                  "var result;"
+                  "var x = 0;"
+                  "hidden_prototype.x = 6;"
+                  "object[Symbol.unscopables] = {x: true};"
+                  "with (object) {"
+                  "  result = x;"
+                  "}"
+                  "result")->Int32Value());
+}
+}

test/mjsunit/harmony/proxies-with-unscopables.js

+// 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.
+
+// Flags: --harmony-unscopables
+// Flags: --harmony-proxies
+
+
+// TODO(arv): Once proxies can intercept symbols, add more tests.
+
+
+function TestBasics() {
+  var log = [];
+
+  var proxy = Proxy.create({
+    getPropertyDescriptor: function(key) {
+      log.push(key);
+      if (key === 'x') {
+        return {
+          value: 1,
+          configurable: true
+        };
+      }
+      return undefined;
+    }
+  });
+
+  var x = 'local';
+
+  with (proxy) {
+    assertEquals(1, x);
+  }
+
+  // One 'x' for HasBinding and one for GetBindingValue
+  assertEquals(['assertEquals', 'x', 'x'], log);
+}
+TestBasics();
+
+
+function TestInconsistent() {
+  var log = [];
+  var calls = 0;
+
+  var proxy = Proxy.create({
+    getPropertyDescriptor: function(key) {
+      log.push(key);
+      if (key === 'x' && calls < 1) {
+        calls++;
+        return {
+          value: 1,
+          configurable: true
+        };
+      }
+      return undefined;
+    }
+  });
+
+  var x = 'local';
+
+  with (proxy) {
+    assertEquals(void 0, x);
+  }
+
+  // One 'x' for HasBinding and one for GetBindingValue
+  assertEquals(['assertEquals', 'x', 'x'], log);
+}
+TestInconsistent();
+
+
+function TestUseProxyAsUnscopables() {
+  var x = 1;
+  var object = {
+    x: 2
+  };
+  var calls = 0;
+  var proxy = Proxy.create({
+    has: function(key) {
+      calls++;
+      assertEquals('x', key);
+      return calls === 2;
+    },
+    getPropertyDescriptor: function(key) {
+      assertUnreachable();
+    }
+  });
+
+  object[Symbol.unscopables] = proxy;
+
+  with (object) {
+    assertEquals(2, x);
+    assertEquals(1, x);
+  }
+
+  // HasBinding, HasBinding
+  assertEquals(2, calls);
+}
+TestUseProxyAsUnscopables();
+
+
+function TestThrowInHasUnscopables() {
+  var x = 1;
+  var object = {
+    x: 2
+  };
+
+  function CustomError() {}
+
+  var calls = 0;
+  var proxy = Proxy.create({
+    has: function(key) {
+      if (calls++ === 0) {
+        throw new CustomError();
+      }
+      assertUnreachable();
+    },
+    getPropertyDescriptor: function(key) {
+      assertUnreachable();
+    }
+  });
+
+  object[Symbol.unscopables] = proxy;
+
+  assertThrows(function() {
+    with (object) {
+      x;
+    }
+  }, CustomError);
+}
+TestThrowInHasUnscopables();
+
+
+var global = this;
+function TestGlobalShouldIgnoreUnscopables() {
+  global.x = 1;
+  var proxy = Proxy.create({
+    getPropertyDescriptor: function() {
+      assertUnreachable();
+    }
+  });
+  global[Symbol.unscopables] = proxy;
+
+  assertEquals(1, global.x);
+  assertEquals(1, x);
+
+  global.x = 2;
+  assertEquals(2, global.x);
+  assertEquals(2, x);
+
+  x = 3;
+  assertEquals(3, global.x);
+  assertEquals(3, x);
+}
+TestGlobalShouldIgnoreUnscopables();

tools/generate-runtime-tests.py

@@ -51,7 +51,7 @@ EXPECTED_FUNCTION_COUNT = 427
 EXPECTED_FUZZABLE_COUNT = 330
 EXPECTED_CCTEST_COUNT = 7
 EXPECTED_UNKNOWN_COUNT = 16
-EXPECTED_BUILTINS_COUNT = 809
+EXPECTED_BUILTINS_COUNT = 811
 
 
 # Don't call these at all.

tools/gyp/v8.gyp

@@ -1417,6 +1417,7 @@
           '../../src/string-iterator.js',
           '../../src/harmony-string.js',
           '../../src/harmony-array.js',
+          '../../src/unscopables.js',
         ],
         'libraries_bin_file': '<(SHARED_INTERMEDIATE_DIR)/libraries.bin',
         'libraries_experimental_bin_file': '<(SHARED_INTERMEDIATE_DIR)/libraries-experimental.bin',