TypeError: Promise._immediateFn is not a function.

[hisaichi5518]

Environment

Plugin version:

  flutter_inappwebview:
    git:
      url: git@github.com:pichillilorenzo/flutter_inappwebview.git
      ref: '9c7ac0d'

I am using 9c7ac0d to solve this issue.
#209 (comment)

iOS version:
iOS 13.1

Device information:
iPhone 11 Pro Max Simulator

 $ flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel beta, v1.12.13+hotfix.6, on Mac OS X 10.15.3 19D76, locale ja-JP)
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
[✓] Xcode - develop for iOS and macOS (Xcode 11.1)
[✓] Android Studio (version 3.5)
[✓] IntelliJ IDEA Ultimate Edition (version 2019.3.2)
[✓] VS Code (version 1.42.0)
[✓] Connected device (2 available)

Description

Expected behavior:

This will set a global Promise object if the browser doesn't already have window.Promise.

Current behavior:

override native Promise object.

Steps to reproduce

1. Use 9c7ac0d
2. Use Promise.resolve() in JavaScript.
3. function is not found Error!

Stacktrace/Logcat

flutter: [CONSOLE.ERROR] TypeError: Promise._immediateFn is not a function. (In 'Promise._immediateFn(function() {
flutter:         if (!self._handled) {
flutter:           Promise._unhandledRejectionFn(self._value);
flutter:         }
flutter:       })', 'Promise._immediateFn' is undefined)

Reason

Overridden in the code below.
https://github.com/pichillilorenzo/flutter_inappwebview/blob/master/ios/Classes/InAppWebView.swift#L57

function Promise(fn) {
    if (!(this instanceof Promise))
      throw new TypeError("Promises must be constructed via new");
    if (typeof fn !== "function") throw new TypeError("not a function");
    this._state = 0;
    this._handled = false;
    this._value = undefined;
    this._deferreds = [];
    doResolve(fn, this);
};

Solution

Using the code at the following URL.
it will not set a global Promise object if the browser already has window.Promise.
https://cdn.jsdelivr.net/npm/promise-polyfill@8/dist/polyfill.min.js

@pichillilorenzo
What do you think about this solution?

[hisaichi5518]

See also

https://stackoverflow.com/questions/57035056/javascript-object-definition-available-before-code-execution-on-safari