fix(worker): handle self reference url worker in dependency for build

[hi-ogawa]

Description

• closes Build fails on self reference worker new Worker(new URL(..., import.meta.url)) in dependency #17843

Oddly this.getModuleInfo(...).isEntry is becoming false when the worker entry is from node_modules. I think we can equivalently check this based on config.bundleChain, so I put this as a quick fix. Probably I'll dig into this further.

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Coming back after some digging, I think what's happening is that rollup is going through following steps:

• rollup({ input: "..../node_modules/.../worker.js", ...}) from bundleWorkerEntry
• rollup calls resolveId(input) but there's no isEntry: true at this point
• commonjs--resolver plugin's resolveId calls this.load(".../node_modules/.../worker.js") (link) which leads to workerImportMetaUrlPlugin.transform. Note that this happens only for dependencies because Vite uses commonjsPlugin({ include: /node_modules/, ... }).

Based on this, I think checking config.bundleChain.at(-1) seems more robust.

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[bluwy]

I think this makes sense and also looks more straightforward to me.

[sapphi-red]

Thanks!

[sbc100]

In emscripten we use the self-references a lot (to start pthread workers).

Would it be possible to allow the shorter form of this which is the even more explicit self reference: new URL(import.meta.url). Its also more portable to write this shorter form since its robust against the containing file getting renamed.

[hi-ogawa]

Yeah, that should work as Vite would skip analysis and don't have to rewrite it.
What Vite does is to detect recursive worker of this form new URL("./some-file", import.meta.url) and rewrite it into new URL(self.location.href), so the runtime can reference it easily.
So any of these should work:

• new Worker(import.meta.url)
• new Worker(new URL(import.meta.url))
• new Worker(self.location.href)

I confirmed it on my repro, but if you see something different, please submit a separate issue to track it.

[sbc100]

Would it be possible to also allow ./index.js here? I.e. a self reference from the main script? This is how emscripten starts its pthread workers. All workers (including the main page) use the same script.

[hi-ogawa]

I think that should work too though one caveat is that Vite needs to bundle index.js twice for main script and as worker script. So, it's likely that some js might got duplicated but IIRC static wasm assets can be de-duped.