[html] support 'import' in <script type=module> tags

[vp2177]

• VSCode Version: 1.38.1 (originally 1.13.1)
• OS Version: any

Steps to Reproduce:

1. Given the files:
   a.js:

/**
 * @param {number} param1
 * @param {string} param2
 */
export function a(param1, param2) {}

index.html:

<script type="module">
  import {a} from './a.js'

  a( )
</script>

2. When typing a(, the type information is not picked up from the definition of a() in a.js.
3. Same works from a JS file

Now that import is beginning to appear in browsers I think handling this would make sense

[Rich-Harris]

Adding a note to say that ideally VSCode would also autocomplete import specifiers in<script> tags, the same way it does in .js and .ts files. Opened #35732 for this, but it was closed as a duplicate of this issue.

[vincentvictoria]

Seems like this issue is vastly ignored.
I have to make a separate js file even if I want to write a short module script in html files because of this issue.
Hope it gets attention.

[bsunderhus]

This feature would fit greatly with HTML Modules proposal

[aeschli]

duplicate of #26338

[Rich-Harris]

Is this a duplicate of #26338? They feel quite different — this issue is about being able to reuse the logic around import that already exists in .js and .ts files, whereas #26338 seems to be about applying intellisense to code that references legacy scripts that e.g. assign to window, which seems like a different (and much hairier!) problem, especially when considering async and defer attributes. Apologies if I've misunderstood.

[aeschli]

@Rich-Harris Not exactly the same, I agree. Both issues are about making HTML following references and configuring the typescript service with additional files. The challenge for both is that we likely need a project understanding as to where to find the files.

[vp2177]

As long as the import URL is relative (import './a.js', import 'a.js', import '../a.js' etc.), then relative to the current file.

If the import URL has a http[s] schema, then potentially fetch the file there.

Isn't the only case that's hard to handle an absolute import URL (import '/a.js' etc.)? In which case, I think the current behaviour is fine, just don't reference that file. It probably isn't in the project root and VSCode has no way to know where it would be served from at runtime.
Potentially add a config option, but I think that's a separate feature request.