v8/test/mjsunit/harmony/proxies-prevent-extensions.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 --harmony-reflect


(function () {
  // No trap.

  var target = {};
  var handler = {};
  var proxy = new Proxy(target, handler);

  assertTrue(Reflect.isExtensible(target));
  assertTrue(Reflect.isExtensible(proxy));
  assertTrue(Reflect.preventExtensions(proxy));
  assertFalse(Reflect.isExtensible(target));
  assertFalse(Reflect.isExtensible(proxy));
})();


(function () {
  // "Undefined" trap.

  var target = {};
  var handler = { preventExtensions: null };
  var proxy = new Proxy(target, handler);

  assertTrue(Reflect.isExtensible(target));
  assertTrue(Reflect.isExtensible(proxy));
  assertTrue(Reflect.preventExtensions(proxy));
  assertFalse(Reflect.isExtensible(target));
  assertFalse(Reflect.isExtensible(proxy));
})();


(function () {
  // Invalid trap.

  var target = {};
  var handler = { preventExtensions: 42 };
  var proxy = new Proxy(target, handler);

  assertThrows(() => {Reflect.preventExtensions(proxy)}, TypeError);
})();


(function () {
  var target = {};
  var handler = { isExtensible() {return "bla"} };
  var proxy = new Proxy(target, handler);

  // Trap returns trueish and target is extensible.
  assertTrue(Reflect.isExtensible(proxy));

  // Trap returns trueish but target is not extensible.
  Reflect.preventExtensions(target);
  assertThrows(() => {Reflect.isExtensible(proxy)}, TypeError);
})();


(function () {
  // Trap returns falsish.

  var target = {};
  var handler = { preventExtensions() {return 0} };
  var proxy = new Proxy(target, handler);

  assertFalse(Reflect.preventExtensions(proxy));
  Reflect.preventExtensions(target);
  assertFalse(Reflect.preventExtensions(proxy));
})();


(function () {
  var target = {};
  var handler = { preventExtensions() {return Symbol()} };
  var proxy = new Proxy(target, handler);

  // Trap returns trueish but target is extensible.
  assertThrows(() => {Reflect.preventExtensions(proxy)}, TypeError);

  // Trap returns trueish and target is not extensible.
  Reflect.preventExtensions(target);
  assertTrue(Reflect.preventExtensions(proxy));
})();