feat(coverage): v8 to track `node:child_process` and `node:worker_threads` contexts by AriPerkkio · Pull Request #9976 · vitest-dev/vitest

AriPerkkio · 2026-03-26T13:36:55Z

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@vitest/browser

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@vitest/browser-playwright

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commit: 2e65953

AriPerkkio · 2026-04-12T10:27:54Z

 import { loadProvider } from './load-provider'

-const session = new inspector.Session()
+let session: inspector.Session | null = null


This used to create unused new Session() on main thread too, oops.

AriPerkkio · 2026-04-13T10:57:16Z


 Collect coverage only for files changed since a specified commit or branch. When set to `true`, it uses staged and unstaged changes.
+
+## coverage.trackProcessAndWorker


Naming this option is difficult. Right now it only covers node:child_process and node:worker_threads, but in future it's likely going to be used for web workers and similar on browser. @hi-ogawa & @sheremet-va - please propose better name here. 🙏

Internally this feature also uses term extendedContextCoverage. 🙃

I don't think worker really fits in here, both child process and a worker thread is a worker in my opinion, at least that's how we defined it for pools, maybe trackProcessAndThreads is more accurate.

I would vote for something like includeSubprocesses/instrumentSubprocesses - subprocess can refer to anything, not just a fork/thread/service worker

In debugging world there is also --follow-forks mode (in C), in vscode it's autoAttachChildProcesses (although it also follows workers)

How about autoAttachChildContext? Or autoAttachWorkers and imply Worker is processes too. 🤔

…eads` contexts

hi-ogawa · 2026-04-22T07:12:36Z

+    }
+
+    if (this.extendedContextCoverageDir) {
+      const filenames = await readdir(this.extendedContextCoverageDir)


This directory doesn't exist when there are no children spawned and this happens:

$ pnpm -C examples/basic test --coverage --coverage.autoAttachWorkers > @vitest/example-test@ test /home/hiroshi/code/others/vitest-wt1/examples/basic > vitest --coverage --coverage.autoAttachWorkers DEV v4.1.4 /home/hiroshi/code/others/vitest-wt1/examples/basic Coverage enabled with v8 ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Unhandled Errors ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Vitest caught 2 unhandled errors during the test run. This might cause false positive tests. Resolve unhandled errors to make sure your tests are not affected. ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Test Run Error ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Error: ENOENT: no such file or directory, scandir '/home/hiroshi/code/others/vitest-wt1/examples/basic/coverage/tmp/af48afe8-e4b0-4810-b7b2-e6dbea470389' ❯ readdir node:internal/fs/promises:956:18 ❯ Object.takeCoverage ../../packages/coverage-v8/dist/index.js:50:22 ❯ TestRunner.testRunner.onAfterRunFiles ../../packages/vitest/dist/chunks/index.DtMvdosS.js:173:20 ❯ startTests ../../packages/runner/dist/chunk-artifact.js:3281:3 ❯ ../../packages/vitest/dist/chunks/base.DuCI8aBZ.js:90:5 ❯ run ../../packages/vitest/dist/chunks/base.DuCI8aBZ.js:81:2 ❯ runBaseTests ../../packages/vitest/dist/chunks/base.DuCI8aBZ.js:200:2 ❯ executeTests ../../packages/vitest/dist/chunks/init-forks.UV3ZQGQH.js:29:4 ❯ execute ../../packages/vitest/dist/chunks/init.D98-gwRW.js:158:3 ❯ process.onMessage ../../packages/vitest/dist/chunks/init.D98-gwRW.js:287:14

hi-ogawa · 2026-04-22T07:30:39Z

+    }
+
+    if (this.extendedContextCoverageDir) {
+      const filenames = await readdir(this.extendedContextCoverageDir)


Also does this ensure the coverage json emitted by children to be collected only once? Looks like multiple takeCoverage calls (maybe isolate false) can read the same json and sent as coverage.

AriPerkkio commented Mar 26, 2026

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Comment thread packages/coverage-v8/src/intercept-new-run-context.ts Outdated

AriPerkkio force-pushed the feat/coverage-process-thread-context branch from 88a5c08 to fa35cd5 Compare March 26, 2026 13:49

AriPerkkio added the cr-tracked label Mar 26, 2026

AriPerkkio force-pushed the feat/coverage-process-thread-context branch 3 times, most recently from fef5aec to 188a95f Compare March 31, 2026 18:35

AriPerkkio force-pushed the feat/coverage-process-thread-context branch 2 times, most recently from 70f7641 to 3d1dce2 Compare April 6, 2026 14:03

AriPerkkio commented Apr 6, 2026

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Comment thread test/coverage-test/test/extended-run-context.v8.test.ts Outdated

AriPerkkio force-pushed the feat/coverage-process-thread-context branch 3 times, most recently from ed25468 to 66e52a1 Compare April 6, 2026 19:31

AriPerkkio commented Apr 7, 2026

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Comment thread packages/coverage-v8/src/index.ts Outdated

AriPerkkio force-pushed the feat/coverage-process-thread-context branch 3 times, most recently from fb7116a to c0a7985 Compare April 12, 2026 09:55

AriPerkkio commented Apr 12, 2026

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AriPerkkio force-pushed the feat/coverage-process-thread-context branch 3 times, most recently from b97e821 to 63acca7 Compare April 13, 2026 09:31

This was referenced Apr 13, 2026

coverage not collected from sub-propcesses result from child_process APIs #7064

Open

@vitest/web-worker error when using browser environment #4899

Open

AriPerkkio marked this pull request as ready for review April 13, 2026 10:52

AriPerkkio force-pushed the feat/coverage-process-thread-context branch from 63acca7 to 92ab430 Compare April 13, 2026 10:55

AriPerkkio commented Apr 13, 2026

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AriPerkkio requested review from hi-ogawa and sheremet-va and removed request for sheremet-va April 13, 2026 10:57

AriPerkkio requested a review from sheremet-va April 13, 2026 10:57

AriPerkkio mentioned this pull request Apr 14, 2026

Add E2E code coverage storybookjs/mcp#156

Draft

AriPerkkio force-pushed the feat/coverage-process-thread-context branch from 92ab430 to c1073e1 Compare April 20, 2026 10:05

AriPerkkio added 2 commits April 21, 2026 08:42

feat(coverage): v8 to track node:child_process and `node:worker_thr…

9832a38

…eads` contexts

fix: rename trackProcessAndWorker to autoAttachWorkers

2eb5e8d

AriPerkkio force-pushed the feat/coverage-process-thread-context branch from c1073e1 to 2eb5e8d Compare April 21, 2026 05:47

AriPerkkio commented Apr 22, 2026

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Comment thread docs/config/coverage.md Outdated

docs: remove experimental status

2e65953

hi-ogawa reviewed Apr 22, 2026

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feat(coverage): v8 to track `node:child_process` and `node:worker_threads` contexts#9976

feat(coverage): v8 to track `node:child_process` and `node:worker_threads` contexts#9976
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		Collect coverage only for files changed since a specified commit or branch. When set to `true`, it uses staged and unstaged changes.

		## coverage.trackProcessAndWorker

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Description

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