preact-cli: Promise polyfill is not applied

Apps created via cli do not work on browsers without Promise implementation. For Windows users the easiest way to reproduce is to open https://clidemo.preactjs.com in IE11 and look into dev console.

This is problems occurs because of polyfills reside in separate chunks - which would be fine if webpack didn’t use Promises in chunk loading code 😆 (which it does and states so in docs).

I’m thinking we can go several ways:

drop non ES2015 browsers support (which means dropping PhantomJS and possibly large part of potential cli users)
load promise polyfill eagerly
load promise polyfill via some custom JS code (dynamic script tag?)

Steps to reproduce

preact create app
cd app
npm run serve
Visit localhost:8080 in browser without ES6 support
Click any navigation link (e.g. Profile)

Expected result:

Page is changed

Actual result:

Nothing happens. Error Promise is not defined is seen in console

About this issue

Original URL
State: closed
Created 7 years ago
Comments: 21 (14 by maintainers)

Most upvoted comments

Was there any resolution on this? @thangngoc89, I’m developing for UC as well and am currently just importing and initializing promise-polyfill in my app.js, which obviously feels ridiculous given that it’s sitting in the polyfills chunk already.

ethanroday on Jun 20, 2017

@thangngoc89 Correct, but in the majority case, Promise is supported already. A conditional tag (as provided) will load before the webpack runtime, which means Promise will always be ready.

lukeed on Jun 8, 2017

@developit good call I haven’t thought about that fetch requires promise implementation.

rkostrzewski on Jun 8, 2017

@developit @rkostrzewski Instead of a defaultAttribute across the board, we can specify a pattern to match everything except ~ promise.polyfill.js (or whatever name).

Also, I would assume that this script be loaded under a HTML conditional:

<!--[if IE]>
 <script src='promise.polyfill.js'></script>
<![endif]-->

lukeed on Jun 8, 2017