fix(pool): prevent writing to closed worker

[AriPerkkio]

Description

Resolves #9014

When user's test case doesn't do proper clean up, it can trigger rpc calls after test finished. In the reproduction there's rpc.fetch() that resolves on main thread after worker has stopped. This leads to EPIPE as IPC is closed already.

This is reproducible by having Vite plugin that takes long time on specific file transform, and that file is imported without awaiting it in test case.

Minimal repro for test/core - this will raise Error: [vitest-worker]: Closing rpc while "fetch" was pending errors on worker side so not adding the test case for now:

import { defineConfig } from 'vitest/config'

export default defineConfig({
  plugins: [
    {
      name: 'slow-down-transform',
      enforce: 'pre',
      async resolveId(id) {
        if (id.includes('vitest-test:slow-transform')) {
          return '\0vitest-test-slow-transform'
        }
      },
      async load(id) {
        if (id.includes('vitest-test-slow-transform')) {
          await new Promise(res => setTimeout(res, 1000))
          return `export default "Hello world"`
        }
      },
    },
  ],
});

import { test } from 'vitest'

test('should not cause EPIPE when imports resolve after test finishes', async () => {
  for (const _ of Array.from({ length: 50 }).fill(0)) {
    const cache = Math.round(Math.random() * 1000)

    setTimeout(
      () =>
        import(`vitest-test:slow-transform` + `?cache=${cache}`),
      2,
    ).unref()
  }
})

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

• It's really useful if your PR references an issue where it is discussed ahead of time. If the feature is substantial or introduces breaking changes without a discussion, PR might be closed.
• Ideally, include a test that fails without this PR but passes with it.
• Please, don't make changes to pnpm-lock.yaml unless you introduce a new test example.
• Please check Allow edits by maintainers to make review process faster. Note that this option is not available for repositories that are owned by Github organizations.

Tests

• Run the tests with pnpm test:ci.

Documentation

• If you introduce new functionality, document it. You can run documentation with pnpm run docs command.

Changesets

• Changes in changelog are generated from PR name. Please, make sure that it explains your changes in an understandable manner. Please, prefix changeset messages with feat:, fix:, perf:, docs:, or chore:.

[pkg-pr-new]

@vitest/browser

npm i https://pkg.pr.new/@vitest/browser@9023

@vitest/browser-playwright

npm i https://pkg.pr.new/@vitest/browser-playwright@9023

@vitest/browser-preview

npm i https://pkg.pr.new/@vitest/browser-preview@9023

@vitest/browser-webdriverio

npm i https://pkg.pr.new/@vitest/browser-webdriverio@9023

@vitest/coverage-istanbul

npm i https://pkg.pr.new/@vitest/coverage-istanbul@9023

@vitest/coverage-v8

npm i https://pkg.pr.new/@vitest/coverage-v8@9023

@vitest/expect

npm i https://pkg.pr.new/@vitest/expect@9023

@vitest/mocker

npm i https://pkg.pr.new/@vitest/mocker@9023

@vitest/pretty-format

npm i https://pkg.pr.new/@vitest/pretty-format@9023

@vitest/runner

npm i https://pkg.pr.new/@vitest/runner@9023

@vitest/snapshot

npm i https://pkg.pr.new/@vitest/snapshot@9023

@vitest/spy

npm i https://pkg.pr.new/@vitest/spy@9023

@vitest/ui

npm i https://pkg.pr.new/@vitest/ui@9023

@vitest/utils

npm i https://pkg.pr.new/@vitest/utils@9023

vitest

npm i https://pkg.pr.new/vitest@9023

@vitest/web-worker

npm i https://pkg.pr.new/@vitest/web-worker@9023

@vitest/ws-client

npm i https://pkg.pr.new/@vitest/ws-client@9023

commit: 93d3e59

[netlify]

✅ Deploy Preview for vitest-dev ready!

Built without sensitive environment variables

Name	Link
🔨 Latest commit	0f9e498
🔍 Latest deploy log	https://app.netlify.com/projects/vitest-dev/deploys/69187bc0d432890008a9f626
😎 Deploy Preview	https://deploy-preview-9023--vitest-dev.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[axel7083]

Hey! So glad to see you working on this issue, we are in the middle of our migration to vitest 4. We have an almost 100% reproducer on GitHub, (not reproducing locally however) if you need to experiment let me know I could try to help

---

I also tried to downgrade to 4.0.4 but the problem still persist unit tests / ubuntu-24.04#job