setImmediate is broken in file:// protocols in iOS.

[dtinth]

Background

We at @taskworld noticed that when our application is running inside Cordova, some Promise would never resolve. Instead, we’d get a weird error message on the console: “Unable to post message to file://. Recipient has origin null.”

Upon further investigation, we found that some of our 3rd-party libraries are using an outdated Promise implementation which depends on setImmediate. setImmediate is broken in Cordova, so I decided to file an issue here in core-js.

Investigation

This situation happens in Cordova apps,

• Web application is run on file:// protocol using Safari’s engine.

• The defer selection logic selects postMessage to be used (MessageChannel is not used due to IS_IOS clause):

  core-js/packages/core-js/internals/task.js

  Lines 61 to 81 in 4546ffe

  	if (classof(process) == 'process') {
  	defer = function (id) {
  	process.nextTick(runner(id));
  	};
  	// Sphere (JS game engine) Dispatch API
  	} else if (Dispatch && Dispatch.now) {
  	defer = function (id) {
  	Dispatch.now(runner(id));
  	};
  	// Browsers with MessageChannel, includes WebWorkers
  	// except iOS - https://github.com/zloirock/core-js/issues/624
  	} else if (MessageChannel && !IS_IOS) {
  	channel = new MessageChannel();
  	port = channel.port2;
  	channel.port1.onmessage = listener;
  	defer = bind(port.postMessage, port, 1);
  	// Browsers with postMessage, skip WebWorkers
  	// IE8 has postMessage, but it's sync & typeof its postMessage is 'object'
  	} else if (global.addEventListener && typeof postMessage == 'function' && !global.importScripts && !fails(post)) {
  	defer = post;
  	global.addEventListener('message', listener, false);

• The postMessage implementation of defer doesn’t work with file: protocol, it errors out with this:

  Unable to post message to file://. Recipient has origin null.
  

Suggested fix

If location.protocol === 'file:', fallback to alternative methods. I made a PR #771 that implements the suggested fix.

Current workaround

require('core-js/stable')

// `setImmediate` is currently broken on Cordova.
// Falling back to `setTimeout` implementation.
//
// See: https://github.com/zloirock/core-js/issues/770
// See also: https://developer.mozilla.org/en-US/docs/Web/API/Window/setImmediate#Notes
//
window.setImmediate = f => {
  setTimeout(f, 0)
}

---

I investigated this issue while working on Taskworld, so gotta plug that in. 😄

[diegodalbosco]

Same problem here. After updating to latest core-js version we cannot deploy our web app to ios (inside a WKWebView that points to local files).

[slowcheetah]

@diegodalbosco try that patch #771
@dtinth thx for solution

[diegodalbosco]

@slowcheetah We tried the patch and for our use case is working 🎉 Thanks @dtinth!