search

guybedford / import-maps-extensions

Extensions to the WICG import maps proposal
Other
37 stars 1 forks source link

Dynamic import maps not working if called asynchronously #7

Closed DmitryBrus closed 3 years ago

DmitryBrus commented 3 years ago

I noticed weird behavior with dynamic-imports-maps extra.

let say we have 2 modules: mod1 and mod2.

import map for the first one pre-registered in index.html

<head>
...
<script type="systemjs-importmap">{"imports":{"mod1":"/mod1/main.js"}}</script>
</head>

Import map for second added dynamically:

const script = document.createElement('script');
script.setAttribute('type', 'systemjs-importmap');
script.text = JSON.stringify({"imports": {"mod2": '/mod2/main.js'}});
document.head.appendChild(script);

this works good in straight sync flow:

System.import('mod1');

const script = document.createElement('script');
script.setAttribute('type', 'systemjs-importmap');
script.text = JSON.stringify({"imports": {"mod2": '/mod2/main.js'}});
document.head.appendChild(script);

System.import('mod2');

But.

if dynamic add and import occurs asynchronously (e.g. after call or simply with setTimeout delay - import fails:

System.import('mod1');

setTimeout(() => {
  const script = document.createElement('script');
  script.setAttribute('type', 'systemjs-importmap');
  script.text = JSON.stringify({"imports": {"mod2": '/mod2/main.js'}});
  document.head.appendChild(script);

  System.import('mod2');
}, 1000);

Unhandled Promise rejection: Unable to resolve bare specifier 'mod2'

if I wrap System.import('mod2') in setTimeout - import succeed, but it looks like workaround,

Does anybody have any ideas why import behaves like that?

I use SystemJS 6.4.3

DmitryBrus commented 3 years ago

Just payed attention that I'm not at systemjs repo, worth to copy it to systemjs?

guybedford commented 3 years ago

Let's track this in https://github.com/systemjs/systemjs/issues/2305. This was just implemented in ES module shims with dom mutators so the same approach can apply to SystemJS.

You were right that the real issue is whether the spec for dynamic map updates as per this repo has a chance of going forward!