[TIMOB-18465] Globals are not (over)writable

GitHub Issue	n/a
Type	Improvement
Priority	None
Status	Open
Resolution	Unresolved
Affected Version/s	Release 3.5.0
Fix Version/s	n/a
Components	iOS
Labels	ios-jscore, kroll, parity
Reporter	Pier Paolo Ramon
Assignee	Christopher Williams
Created	2015-01-29T09:26:28.000+0000
Updated	2019-04-26T19:04:21.000+0000

Description

Currently globals are not set with the ‘right’ flags. We cannot actually say right or wrong flags, because they’re not in the EcmaScript definition. Some discussion happened on https://github.com/smclab/titaniumifier/issues/31. The code to test the descriptors is the following:

var global = (function () { return this; }());

if ((typeof window !== 'undefined') &&
    (window === global) &&
    (!window.hasOwnProperty('alert'))) {
  // In the browser the globals are not directly in the window, but in the
  // prototype chain
  global = Object.getPrototypeOf(global);
}

printPropertyDescriptor(global, 'alert');

printPropertyDescriptor(global, 'setTimeout');
printPropertyDescriptor(global, 'clearTimeout');
printPropertyDescriptor(global, 'setInterval');
printPropertyDescriptor(global, 'clearInterval');

function printPropertyDescriptor(obj, name) {
	var descriptor = Object.getOwnPropertyDescriptor(obj, 'clearTimeout');
	var formatted = JSON.stringify(descriptor, null, 2);
	console.log(name + " = " + formatted);
}

The result is different in every environment. As you will see only Titanium *on iOS* is setting the properties as non-writable. Also, if using "use strict" trying to overwrite those properties will result in an error thrown. *Node.js*

alert = {
  "writable": true,
  "enumerable": true,
  "configurable": true
}
setTimeout = {
  "writable": true,
  "enumerable": true,
  "configurable": true
}
clearTimeout = {
  "writable": true,
  "enumerable": true,
  "configurable": true
}
setInterval = {
  "writable": true,
  "enumerable": true,
  "configurable": true
}
clearInterval = {
  "writable": true,
  "enumerable": true,
  "configurable": true
}

*Chrome*

alert = {
  "writable": true,
  "enumerable": true,
  "configurable": false
}
setTimeout = {
  "writable": true,
  "enumerable": true,
  "configurable": false
}
clearTimeout = {
  "writable": true,
  "enumerable": true,
  "configurable": false
}
setInterval = {
  "writable": true,
  "enumerable": true,
  "configurable": false
}
clearInterval = {
  "writable": true,
  "enumerable": true,
  "configurable": false
}

*Firefox*

alert = {
  "configurable": true,
  "enumerable": true,
  "writable": true
}
setTimeout = {
  "configurable": true,
  "enumerable": true,
  "writable": true
}
clearTimeout = {
  "configurable": true,
  "enumerable": true,
  "writable": true
}
setInterval = {
  "configurable": true,
  "enumerable": true,
  "writable": true
}
clearInterval = {
  "configurable": true,
  "enumerable": true,
  "writable": true
}

*Titanium Android*

alert = {
  "writable": true,
  "enumerable": true,
  "configurable": true
}
setTimeout = {
  "writable": true,
  "enumerable": true,
  "configurable": true
}
clearTimeout = {
  "writable": true,
  "enumerable": true,
  "configurable": true
}
setInterval = {
  "writable": true,
  "enumerable": true,
  "configurable": true
}
clearInterval = {
  "writable": true,
  "enumerable": true,
  "configurable": true
}

*Titanium iOS* (drumroll)

alert = {
  "writable": false,
  "enumerable": true,
  "configurable": false
}
setTimeout = {
  "writable": false,
  "enumerable": true,
  "configurable": false
}
clearTimeout = {
  "writable": false,
  "enumerable": true,
  "configurable": false
}
setInterval = {
  "writable": false,
  "enumerable": true,
  "configurable": false
}
clearInterval = {
  "writable": false,
  "enumerable": true,
  "configurable": false
}

Comments

Pier Paolo Ramon 2015-01-29

Here’s the culprit: https://github.com/appcelerator/titanium_mobile/blob/2c7f6fb74fa772e1ecc8d9d5209f83c4a0c06aab/iphone/Classes/KrollContext.m#L1112 Why are them explicitly set as kTiPropertyAttributeReadOnly | kTiPropertyAttributeDontDelete? There’s no (real) reason for doing this…

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