cannot import javascript files and local dependencies from web workers

[m4rch3n1ng]

Describe the bug

i have created a default, vite template svelte (with typescript) and i am trying to import a Worker (from src/lib/worker.js, that imports code from both a local file (src/lib/test.ts) and a local dependency ("comlink"). in dev mode it works fine but after building and running it using a static file server (for example sirv-cli) it silently fails (i.e. just doesn't execute). if i remove the imports to local files (like i have in the fix branch) it works again.

note: since this i have only tested this with svelte configuration (both regular vite svelte and svelte-kit) the issue might come from the svelte plugin for vite (@sveltejs/vite-plugin-svelte), but since the transpiling is done by vite i suspect the issue comes from here

Reproduction

https://github.com/m4rch3n1ng/vite-webworker-bug-reproduction

Steps to reproduce

info

if you see two console logs, one labeled as "App.svelte" and one labeled as "worker.js", then it's working.
if you only see the "App.svelte" console log then the web worker is not working

broken

$ git switch main
$ npm install
$ npm run build
$ npx sirv-cli dist

works in dev mode

$ npm run dev

fix (annoying and non-optimal)

$ git switch fix
$ npm install
$ npm run buid
$ npx sirv-cli dist

System Info

System:
    OS: Linux 6.2 Arch Linux
    CPU: (6) x64 Intel(R) Core(TM) i5-8400 CPU @ 2.80GHz
    Memory: 8.33 GB / 15.56 GB
    Container: Yes
    Shell: 3.6.1 - /usr/bin/fish
  Binaries:
    Node: 19.8.1 - /usr/bin/node
    Yarn: 1.22.19 - ~/.local/bin/yarn
    npm: 9.6.3 - ~/.local/bin/npm
  Browsers:
    Chromium: 112.0.5615.49
  npmPackages:
    vite: ^4.2.0 => 4.2.1

Used Package Manager

npm

Logs

No response

Validations

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• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to vuejs/core instead.
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• The provided reproduction is a minimal reproducible example of the bug.

[sapphi-red]

Duplicate of #6757

Currently Vite doesn't bundle files imported with ?url and simply treats as a simple asset.
A workaround is to use: new Worker(new URL('./worker.js', import.meta.url), { type: "module" }) (docs).

[m4rch3n1ng]

thank you so much, i do think it should be explicitly stated in the docs that imports like that don't actually get bundled.
i didn't think to use the new URL method, since that threw a build error on my production build (and i forgot to test in the reproduction) but that seems to be the fault of sveltejs/kit#9528.