test/mjsunit/error-constructors.js

// Copyright 2011 the V8 project authors. All rights reserved.
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var e = new Error();
assertFalse(e.hasOwnProperty('message'));
Error.prototype.toString = Object.prototype.toString;
assertEquals("[object Error]", Error.prototype.toString());
assertEquals(Object.prototype, Error.prototype.__proto__);

// Check that error construction does not call setters for the
// properties on error objects in prototypes.
function fail() { assertTrue(false); };
ReferenceError.prototype.__defineSetter__('stack', fail);
ReferenceError.prototype.__defineSetter__('message', fail);
ReferenceError.prototype.__defineSetter__('type', fail);
ReferenceError.prototype.__defineSetter__('arguments', fail);
var e0 = new ReferenceError();
var e1 = new ReferenceError('123');
assertTrue(e1.hasOwnProperty('message'));
assertTrue(e0.hasOwnProperty('stack'));
assertTrue(e1.hasOwnProperty('stack'));
assertTrue(e0.hasOwnProperty('type'));
assertTrue(e1.hasOwnProperty('type'));
assertTrue(e0.hasOwnProperty('arguments'));
assertTrue(e1.hasOwnProperty('arguments'));

// Check that the name property on error prototypes is read-only and
// dont-delete. This is not specified, but allowing overwriting the
// name property with a getter can leaks error objects from different
// script tags in the same context in a browser setting. We therefore
// disallow changes to the name property on error objects.
assertEquals("ReferenceError", ReferenceError.prototype.name);
delete ReferenceError.prototype.name;
assertEquals("ReferenceError", ReferenceError.prototype.name);
ReferenceError.prototype.name = "not a reference error";
assertEquals("ReferenceError", ReferenceError.prototype.name);

// Check that message and name are not enumerable on Error objects.
var desc = Object.getOwnPropertyDescriptor(Error.prototype, 'name');
assertFalse(desc['enumerable']);
desc = Object.getOwnPropertyDescriptor(Error.prototype, 'message');
assertFalse(desc['enumerable']);

var e = new Error("foobar");
desc = Object.getOwnPropertyDescriptor(e, 'message');
assertFalse(desc['enumerable']);
desc = Object.getOwnPropertyDescriptor(e, 'arguments');
assertFalse(desc['enumerable']);
desc = Object.getOwnPropertyDescriptor(e, 'type');
assertFalse(desc['enumerable']);
desc = Object.getOwnPropertyDescriptor(e, 'stack');
assertFalse(desc['enumerable']);

// name is not tested above, but in addition we should have no enumerable
// properties, so we simply assert that.
for (var v in e) {
  assertUnreachable();
}