Bug Involving queueMicrotask

[stephahart]

"@babel/core": "^7.14.0"
"@babel/preset-env": "^7.14.0"
"core-js": "^3.11.1"

Testing on iOS 10.3.2 in (Mobile Safari 10.0):

// modern engines have queueMicrotask method
if (!queueMicrotask) {
  flush = function () {
    var parent, fn;
    if (IS_NODE && (parent = process.domain)) parent.exit();
    while (head) {
      alert(JSON.stringify(head)); // inifinite loop, where head evaluates to "{}"
      fn = head.fn;
      head = head.next;
      try {
        fn();
      } catch (error) {
        if (head) notify();
        else last = undefined;
        throw error;
      }
    } last = undefined;
    if (parent) parent.enter();
  };

In this excerpt of code, I'm somehow getting stuck in a loop where alert(JSON.stringify(head)) constantly evaluates to false.

I'm not able to debug more, but this code is also triggered in my dev environment:

  // environments with maybe non-completely correct, but existent Promise
  } else if (Promise && Promise.resolve) {
    // Promise.resolve without an argument throws an error in LG WebOS 2
    promise = Promise.resolve(undefined);
    then = promise.then;
    notify = function () {
      then.call(promise, flush);
    };
  } ...

[stephahart]

This issue is not present in version 3.11.0.

[zloirock]

Try 3.11.2.