fix!: worker.plugins is a function

[patak-dev]

Fixes #13367

Description

This is a breaking change, changing the signature of worker.plugins to be a function instead of an array of plugins.

import myWorkerPlugin from 'my-worker-plugin';

export default {
   worker: {
      plugins: () => [myWorkerPlugin()]
   }
}

We move to a function to be able to get a fresh array of plugins every time we need to bundle a worker entry with rollup during build. This allows us to revert #11218 and have workers bundling in parallel.

The PR adds some of the tests from #14113 (has @jamsinclair as co-author).

mergeConfig is also modified so worker.plugins is merged as if it were an array.

worker.plugins() modifications in the config hook to config.worker will be ignored.

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

[stackblitz]

Run & review this pull request in StackBlitz Codeflow.

[patak-dev]

/ecosystem-ci run

[vite-ecosystem-ci]

📝 Ran ecosystem CI: Open

suite	result
analogjs	✅ success
astro	❌ failure
histoire	✅ success
ladle	✅ success
laravel	✅ success
marko	❌ failure
nuxt	✅ success
nx	❌ failure
previewjs	✅ success
qwik	❌ failure
rakkas	✅ success
sveltekit	❌ failure
unocss	✅ success
vike	❌ failure
vite-plugin-pwa	❌ failure
vite-plugin-react	✅ success
vite-plugin-react-pages	✅ success
vite-plugin-react-swc	✅ success
vite-plugin-svelte	✅ success
vite-plugin-vue	✅ success
vite-setup-catalogue	✅ success
vitepress	✅ success
vitest	❌ failure

[bluwy]

General logic looks good to me 👍 Got a couple suggestions below to improve a bit.

[bluwy]

Maybe we can move the workers resolve code as a function like resolveWorkerOptions? So it fits the pattern like the other more complex options. Might need a new file beside config.ts.

[patak-dev]

I thought about that but it is using internal functions like filterPlugin, and I wanted to avoid changing unrelated parts on this PR. Maybe we could do that refactoring in another PR?

[patak-dev]

It seems the errors in ecosystem-ci aren't related to this PR, the same fails are right now in main.

[sapphi-red]

Looks mostly good 👍 I have small suggestions and a question.

[sapphi-red]

Maybe it's useful if there's a debug log here that shows the plugin names like we had here?
https://github.com/vitejs/vite/pull/14685/files#diff-11e17761d4ecfee8f8fde15c6d79b7bc0260176396a30dfd8e6f6bbaf5af4745R829

[patak-dev]

We need to see how to do this only once because it will be too noisy if not having the logs everytime for projects that have a lot of workers. I'd say we merge it so it is part of the release and do this in a future PR.