Building ?worker works in dev but bundling with Terser errors

[modderme123]

Describe the bug

When using Terser and Workers on non-trivial dependencies, vite seems to exhibit a concurrency bug which causes terser to error and forces the bundle to stop. However, this bug is particularly confusing for developers because it doesn't mention terser at all! Instead, it says

Unexpected early exit. This happens when Promises returned by plugins cannot resolve. Unfinished hook action(s) on exit:
(vite:worker) transform "vitebug/node_modules/.pnpm/monaco-editor@0.34.0/node_modules/monaco-editor/esm/vs/language/typescript/ts.worker.js?worker"

Ideally whatever error terser is causing should be correctly logged (and terser shouldn't error on this worker bundle).

I've tried to figure out what error is stopping the build but it seems like importing terser just immediately halts the worker with no errors logged

I also tested this bug on stackblitz and it seems that it is missing the on("beforeExit") nodejs feature so doesn't log anything and instead silently outputs nothing: https://stackblitz.com/edit/vite-workers-bug

Reproduction

https://github.com/modderme123/vitebug/

System Info

System:
    OS: macOS 12.5
    CPU: (8) x64 Intel(R) Core(TM) i7-6920HQ CPU @ 2.90GHz
    Memory: 17.69 MB / 16.00 GB
    Shell: 3.5.1 - /usr/local/bin/fish
  Binaries:
    Node: 18.7.0 - /usr/local/bin/node
    npm: 8.16.0 - /usr/local/bin/npm
  Browsers:
    Chrome: 103.0.5060.134
    Safari: 15.6
  npmPackages:
    vite: ^3.0.4 => 3.0.4

Used Package Manager

pnpm

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.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[modderme123]

Related: #1927, #2689

In that case the asset plugin finish was being called twice and wiping the outputted assets (sort of like a use after free).

[pastelmind]

I had a similar issue when using the following import syntax for web workers.

import MyWorker from './path/to/my-worker?worker'
const worker = new MyWorker()

This caused the build to fail in GitHub Actions with a similar error message as the one described by @modderme123.

We worked around the issue by using the ?url syntax:

import MyWorkerUrl from './path/to/my-worker?url'
const worker = new Worker(MyWorkerUrl, { type: 'module' })

[pastelmind]

...and I'm running into a different bug. In the generated bundle, the web worker is encoded as a data URL with the wrong MIME type: data:video/mp2t;base64,aW1wb3.... This seems to be related to #2642 and #4167--

[sapphi-red]

Closing as I confirmed this is fixed from 4.0.0-beta.1. I guess #11218 fixed this.