test262/test/built-ins/Object/defineProperty/15.2.3.6-4-9.js

// Copyright (c) 2012 Ecma International.  All rights reserved.
// Ecma International makes this code available under the terms and conditions set
// forth on http://hg.ecmascript.org/tests/test262/raw-file/tip/LICENSE (the
// "Use Terms").   Any redistribution of this code must retain the above
// copyright and this notice and otherwise comply with the Use Terms.

/*---
info: >
    Step 4 of defineProperty calls the [[DefineOwnProperty]] internal method
    of O to define the property. Step 7b of [[DefineOwnProperty]] rejects if
    current.[[Enumerable]] and desc.[[Enumerable]] are the boolean negations
    of each other.
es5id: 15.2.3.6-4-9
description: >
    Object.defineProperty throws TypeError when changing
    [[Enumerable]] from true to false on non-configurable data
    properties
includes: [runTestCase.js]
---*/

function testcase() {
  var o = {};

  // create a data valued property with [[Enumerable]] explicitly set to true;
  // all other attributes default to false.
  var d1 = { value: 101, enumerable: true, configurable: false };
  Object.defineProperty(o, "foo", d1);

  // now, setting enumerable to false should fail, since [[Configurable]]
  // on the original property will be false.
  var desc = { value: 101, enumerable: false };

  try {
    Object.defineProperty(o, "foo", desc);
  }
  catch (e) {
    if (e instanceof TypeError) {
      // the property should remain unchanged.
      var d2 = Object.getOwnPropertyDescriptor(o, "foo");
      if (d2.value === 101 &&
          d2.enumerable === true &&
          d2.configurable === false) {
        return true;
      }
    }
  }
 }
runTestCase(testcase);