ES6 Unscopables

test/mjsunit/harmony/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
+
+var global = this;
+var globalProto = Object.getPrototypeOf(global);
+
+
+function runtTest(f) {

[rossberg, 2014/07/17 15:12:13]

Nit: s/runtTest/runTest/

[arv (Not doing code reviews), 2014/07/17 23:34:36]

Done.

+  function restoreGlobal() {
+    Object.setPrototypeOf(global, globalProto);
+    delete global[Symbol.unscopables];
+    delete global.x;
+    delete global.x_;
+    delete global.y;
+    delete global.z;
+  }
+
+  function getObject(i) {
+    switch (i) {
+      case 0: return {};

[rossberg, 2014/07/17 15:12:13]

Why not simply use an array? Then you don't need to hardcode 4 below either.

Perhaps add a couple more cases, and maybe a few different cases of property
names as well. For example, the matrix that we test for O.o:

var objects = [
  {},
  [],
  function(){},
  (function(){ return arguments })(),
  (function(){ "use strict"; return arguments })(),
  Object(1), Object(true), Object("bla"),
  new Date(),
  Object, Function, Date, RegExp,
  new Set, new Map, new WeakMap,
  new ArrayBuffer(10), new Int32Array(5),
  global
];
var properties = ["a", "1", 1, "length", "prototype", "name", "caller"];

Would also be good to have the @@unscopable object itself iterate through the
`objects` list. And to install the properties on the @@unscopables as accessors
as well (particular ones without getters). :)

You may think that this should obviously work, but you never know in V8...

[arv (Not doing code reviews), 2014/07/17 23:34:37]

These needs to be new objects every time but I agree that the switch is an
unnecessary optimization.

+      case 1: return [];
+      case 2: return function() {};
+      case 3: return global;
+    }
+  }
+
+  if (f.length === 1) {
+    for (var i = 0; i < 4; i++) {
+      f(getObject(i));
+      restoreGlobal();
+    }
+  } else {
+    for (var i = 0; i < 4; i++) {
+      for (var j = 0; j < 4; j++) {
+        var object = getObject(i);
+        var proto = getObject(i);

[rossberg, 2014/07/17 15:12:13]

getObject(j) ? Otherwise, you don't execute anything. ;)

[arv (Not doing code reviews), 2014/07/17 23:34:37]

wow. That refactoring just completely failed.

+        if (object === proto) {
+          continue;
+        }
+        f(getObject(i), getObject(j));

[rossberg, 2014/07/17 15:12:13]

f(object, proto) ?

[arv (Not doing code reviews), 2014/07/17 23:34:37]

Done.

+        restoreGlobal();
+      }
+    }
+  }
+}
+
+
+function TestBasics(object) {
+  var x = 1;
+  var y = 2;
+  var z = 3;
+  object.x = 4;
+  object.y = 5;
+
+  with (object) {
+    assertEquals(4, x);
+    assertEquals(5, y);
+    assertEquals(3, z);
+  }
+
+  object[Symbol.unscopables] = {x: true};
+  with (object) {
+    assertEquals(1, x);
+    assertEquals(5, y);
+    assertEquals(3, z);
+  }
+
+  object[Symbol.unscopables] = {x: 0, y: true};
+  with (object) {
+    assertEquals(1, x);
+    assertEquals(2, y);
+    assertEquals(3, z);
+  }
+}
+runtTest(TestBasics);
+
+
+function TestBasicsSet(object) {
+  var x = 1;
+  object.x = 2;
+
+  with (object) {
+    assertEquals(2, x);
+  }
+
+  object[Symbol.unscopables] = {x: true};
+  with (object) {
+    assertEquals(1, x);
+    x = 3;
+    assertEquals(3, x);
+  }
+
+  assertEquals(3, x);
+  assertEquals(2, object.x);
+}
+runtTest(TestBasicsSet);
+
+
+function TestOnProto(object, proto) {
+  var x = 1;
+  var y = 2;
+  var z = 3;
+  proto.x = 4;
+
+  Object.setPrototypeOf(object, proto);
+  object.y = 5;
+
+  with (object) {
+    assertEquals(4, x);
+    assertEquals(5, y);
+    assertEquals(3, z);
+  }
+
+  proto[Symbol.unscopables] = {x: true};
+  with (object) {
+    assertEquals(1, x);
+    assertEquals(5, y);
+    assertEquals(3, z);
+  }
+
+  object[Symbol.unscopables] = {y: true};
+  with (object) {
+    assertEquals(1, x);
+    assertEquals(2, y);
+    assertEquals(3, z);
+  }
+
+  proto[Symbol.unscopables] = {y: true};
+  object[Symbol.unscopables] = {x: true};
+  with (object) {
+    assertEquals(4, x);
+    assertEquals(5, y);
+    assertEquals(3, z);
+  }
+}
+runtTest(TestOnProto);
+
+
+function TestNonObject(object) {
+  var x = 1;
+  var y = 2;
+  object.x = 3;
+  object.y = 4;
+
+  object[Symbol.unscopables] = 'xy';
+  with (object) {
+    assertEquals(3, x);
+    assertEquals(4, y);
+  }
+
+  object[Symbol.unscopables] = null;
+  with (object) {
+    assertEquals(3, x);
+    assertEquals(4, y);
+  }
+}
+runtTest(TestNonObject);
+
+
+function TestChangeDuringWith(object) {
+  var x = 1;
+  var y = 2;
+  object.x = 3;
+  object.y = 4;
+
+  with (object) {
+    assertEquals(3, x);
+    assertEquals(4, y);
+    object[Symbol.unscopables] = {x: true};
+    assertEquals(1, x);
+    assertEquals(4, y);
+  }
+}
+runtTest(TestChangeDuringWith);
+
+
+function TestChangeDuringWithWithPossibleOptimization(object) {

[rossberg, 2014/07/17 15:12:13]

I had in mind a test like the following:

var x = 1
object.x = 2
with (object) {
  for (var i = 0; i < 10000; i++) {
    if (i === 500) object[Symbol.unscopables] = {x: true}
    assertEquals(i < 500 ? 1 : 2, x);
  }
}

and dually,

var x = 1
object.x = 2
object[Symbol.unscopables] = {x: true}
with (object) {
  for (var i = 0; i < 10000; i++) {
    if (i === 500) delete object[Symbol.unscopables]
    assertEquals(i < 500 ? 2 : 1, x);
  }
}

and perhaps also the variants

var x = 1
object.x = 2
object[Symbol.unscopables] = {}
with (object) {
  for (var i = 0; i < 10000; i++) {
    if (i === 500) object[Symbol.unscopables].x = true
    assertEquals(i < 500 ? 2 : 1, x);
  }
}

and

var x = 1
object.x = 2
object[Symbol.unscopables] = {x: true}
with (object) {
  for (var i = 0; i < 10000; i++) {
    if (i === 500) delete object[Symbol.unscopables].x
    assertEquals(i < 500 ? 2 : 1, x);
  }
}

The point being that lookup is always for the same variable reference `x` in the
code -- which changes its meaning over time, however.

[arv (Not doing code reviews), 2014/07/17 23:34:37]

Thanks. Added.

+  var x = 1;
+  object.x = 2;
+
+  with (object) {
+    for (var i = 0; i < 1e3; i++) {
+      assertEquals(2, x);
+    }
+    object[Symbol.unscopables] = {x: true};
+    for (var i = 0; i < 1e3; i++) {
+      assertEquals(1, x);
+    }
+  }
+}
+runtTest(TestChangeDuringWithWithPossibleOptimization);
+
+
+var global = this;
+(function TestGlobal() {
+  global.values = 'global.values';
+  Array.prototype.values = 'Array.prototype.values';
+  Array.prototype[Symbol.unscopables] = {values: true};
+  Array.prototype.__proto__ = {values: 42};
+  var array = [];
+  with (array) {
+    assertEquals(42, values);
+  }
+})();
+
+
+function TestAccessorReceiver(object, proto) {
+  var x = 'local';
+
+  Object.defineProperty(proto, 'x', {
+    get: function() {
+      assertEquals(object, this);
+      return this.x_;
+    },
+    configurable: true
+  });
+  proto.x_ = 'proto';
+
+  Object.setPrototypeOf(object, proto);
+  proto.x_ = 'object';
+
+  with (object) {
+    assertEquals('object', x);
+  }
+}
+runtTest(TestAccessorReceiver);
+
+
+function TestUnscopablesGetter(object) {
+  // This test gets really messy when object is the global since the assert
+  // functions are properties on the global object and the call count gets
+  // completely different.
+  if (object === global) return;
+
+  var x = 'local';
+  object.x = 'object';
+
+  var callCount = 0;
+  Object.defineProperty(object, Symbol.unscopables, {
+    get: function() {
+      callCount++;
+      return {};
+    },
+    configurable: true
+  });
+  with (object) {
+    assertEquals('object', x);
+  }
+  // Once for HasBinding and once for GetBindingValue
+  assertEquals(2, callCount);
+
+  callCount = 0;
+  Object.defineProperty(object, Symbol.unscopables, {
+    get: function() {
+      callCount++;
+      return {x: true};
+    },
+    configurable: true
+  });
+  with (object) {
+    assertEquals('local', x);
+  }
+  // Once for HasBinding
+  assertEquals(1, callCount);
+
+  callCount = 0;
+  Object.defineProperty(object, Symbol.unscopables, {
+    get: function() {
+      callCount++;
+      return callCount === 1 ? {} : {x: true};
+    },
+    configurable: true
+  });
+  with (object) {
+    assertEquals(void 0, x);
+  }
+  // Once for HasBinding, once for GetBindingValue.
+  assertEquals(2, callCount);
+
+  callCount = 0;
+  Object.defineProperty(object, Symbol.unscopables, {
+    get: function() {
+      callCount++;
+      return callCount === 1 ? {} : {x: true};
+    },
+    configurable: true
+  });
+  with (object) {
+    x = 1;
+  }
+  // Once for HasBinding
+  assertEquals(1, callCount);
+  assertEquals(1, object.x);
+  assertEquals('local', x);
+  with (object) {
+    x = 2;
+  }
+  // One more HasBinding.
+  assertEquals(2, callCount);
+  assertEquals(1, object.x);
+  assertEquals(2, x);
+}
+runtTest(TestUnscopablesGetter);
+
+
+var global = this;
+(function TestUnscopablesGetter2() {
+  var x = 'local';
+
+  var protos = [{}, [], function() {}, global];
+  var objects = [{}, [], function() {}];
+
+  protos.forEach(function(proto) {
+    objects.forEach(function(object) {
+      Object.defineProperty(proto, 'x', {
+        get: function() {
+          assertEquals(object, this);
+          return 'proto';
+        },
+        configurable: true
+      });
+
+      object.__proto__ = proto;
+      Object.defineProperty(object, 'x', {
+        get: function() {
+          assertEquals(object, this);
+          return 'object';
+        },
+        configurable: true
+      });
+
+      with (object) {
+        assertEquals('object', x);
+      }
+
+      object[Symbol.unscopables] = {x: true};
+      with (object) {
+        assertEquals('proto', x);
+      }
+
+      delete proto[Symbol.unscopables];
+      delete object[Symbol.unscopables];
+    });
+  });
+})();
+
+
+function TestSetterOnBlacklisted(object, proto) {
+  Object.defineProperty(proto, 'x', {
+    set: function(x) {
+      assertTrue(false);

[rossberg, 2014/07/17 15:12:13]

assertUnreachable()

[arv (Not doing code reviews), 2014/07/17 23:34:37]

Done.

+    },
+    get: function() {
+      return 'proto';
+    },
+    configurable: true
+  });
+  Object.setPrototypeOf(object, proto);
+  Object.defineProperty(object, 'x', {
+    get: function() {
+      return this.x_;
+    },
+    set: function(x) {
+      this.x_ = x;
+    },
+    configurable: true
+  });
+  object.x_ = 1;
+
+  with (object) {
+    x = 2;
+    assertEquals(2, x);
+  }
+
+  assertEquals(2, object.x);
+
+  object[Symbol.unscopables] = {x: true};
+
+  with (object) {
+    x = 3;

[rossberg, 2014/07/17 15:12:13]

Yeah, what this does is really weird...

[arv (Not doing code reviews), 2014/07/17 23:34:37]

Acknowledged.

+    assertEquals('proto', x);
+  }
+
+  assertEquals(3, object.x);
+}
+runtTest(TestSetterOnBlacklisted);