Allow running tests in child processes by liuxingbaoyu · Pull Request #17486 · babel/babel

liuxingbaoyu · 2025-08-21T20:04:21Z

Q	A
Fixed Issues?	`Fixes #1, Fixes #2`
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

This is in preparation for Babel 8.
After we clean up our Babel 7 code, we still want to test compatibility with older Node.js versions.
This also makes it easier for local development, as we can now quickly test compatibility with older versions.

Usage: cross-env EXEC_TESTS_NODE=16 yarn jest

babel-bot · 2025-08-21T20:06:42Z

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/61828

pkg-pr-new · 2025-08-21T20:22:58Z

Open in StackBlitz

commit: 2db29ec

nicolo-ribaudo

Nice!

JLHwung · 2025-09-18T20:15:18Z

+  return new Promise((resolve, reject) => {
+    if (!(globalThis as any).worker) {
+      const workerFile = path.join(dirname, "worker.js");
+      const worker = ((globalThis as any).worker = spawn("fnm", [


I am on the fence with the introduction of a new node version manager for the test purpose, if the fnm website is down the whole CI pipeline will be blocked, too. And it is not very efficient that every babel-8-exec test pipeline has to install a version manager.

Would it be possible to make EXEC_TESTS_NODE independent of the node version manager? For example let EXEC_TESTS_NODE_BIN be the path to the exec test node binary, then we can directly pass it to spawn. Doing so should reduce the runtime overhead of the version manager since we have thousands of exec tests.

The path to the node binary should be easily obtained from any node version manager. With this approach, we may just use the node 6 installed from the setup-node action, it is likely provided in the CI runner toolchain, too.

Doing so should reduce the runtime overhead of the version manager since we have thousands of exec tests.

We only initialize one worker for each child process, and the total number of workers in CI should be 2 or 4. :)

Whether EXEC_TESTS_NODE_BIN is supported depends on whether setup-node caches compressed, which is a bit more complicated if they are compressed.

There seems to be no good way to get the path to other versions of setup-node.

Initially, I also didn't want to rely on a package manager, but unfortunately, tools like esvu don't provide NodeJS support.

What if we used n, which can be installed through npm?

There seems to be no good way to get the path to other versions of setup-node.

After we checked out the legacy node version via setup-node, could we write the result of which node to the github output? Then we can enable the latest node version and pass that output to the test step.

What if we used n, which can be installed through npm?

Unfortunately it doesn't support Windows.

I don't really know what are we doing in this PR, but this comment seems talking about execute in different node version. Can this lib be useful https://github.com/ehmicky/nve? Just ignore me if it doesn't.

Amazing! Thank you!
The same author's https://github.com/ehmicky/get-node seems to be what we need.

Fyi Yarn just announced v6, which will also support switching Node.js version.

It will take a while to migrate however, because we have to rewrite our plugins.

https://yarn6.netlify.app/blog/2026-01-28-yarn-6-preview/

Yarn is great, but...
I can't run yarn install in Yarn v1, and can't run yarn run in Yarn v3.🤦‍♂️

yarnpkg/yarn#7940
yarnpkg/berry#6999

liuxingbaoyu · 2025-09-19T16:15:59Z

One issue I've noticed is that this PR contains breaking changes (using transform in tests is no longer supported, and runCodeInTestContext no longer includes Babel helpers).
I'm a bit concerned about people relying on this package.

liuxingbaoyu · 2026-01-27T22:02:49Z

        uses: codecov/codecov-action@v5
        with:
          token: ${{ secrets.CODECOV_TOKEN }}
-          name: babel-7
+          name: babel-8


We should probably do this.

fisker · 2026-01-31T14:17:40Z

+  child_process.spawnSync(
+    `./node_modules/.bin/get-node ${process.env.EXEC_TESTS_NODE}`
+  );
+}


Prettier uses make-synchronized to such job https://github.com/prettier/prettier/blob/cc38e7430dc43925b88c5a63225484db423a5c7a/tests/config/install-browser.js#L3

liuxingbaoyu · 2026-05-26T11:44:06Z

#12728 (comment)
I've encountered this issue again.🤦‍♀️

Copilot

Pull request overview

This PR updates Babel’s test infrastructure to optionally run exec.js fixture tests in a separate Node.js process/version (via EXEC_TESTS_NODE), enabling compatibility testing with older Node releases while keeping the main Jest runtime on a modern Node.

Changes:

Add a worker-based execution path for fixture exec.js tests, with optional spawning via get-node when EXEC_TESTS_NODE is set.
Update/relocate a number of fixture exec tests into Jest suites and add new source map coverage tests.
Adjust build/CI configuration to bundle the new worker entrypoint and add a CI job that runs exec tests using Node v6.

Reviewed changes

Copilot reviewed 40 out of 42 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
yarn.lock	Lockfile updates for newly introduced dependencies (e.g. get-node/get-node-cli, expect@24 alias, etc.).
scripts/pack-script.ts	Expand Rollup node-resolve export conditions used during packing.
packages/babel-plugin-transform-regenerator/test/fixtures/regression/17425/output.js	Update async rejection assertion form in fixture output.
packages/babel-plugin-transform-regenerator/test/fixtures/regression/17425/input.js	Update async rejection assertion form in fixture input.
packages/babel-plugin-transform-regenerator/test/fixtures/regression/17425/exec.js	Update async rejection assertion form in fixture exec.
packages/babel-plugin-transform-modules-commonjs/test/source-map.js	Add Jest test asserting source map mappings are produced.
packages/babel-plugin-transform-modules-commonjs/test/fixtures/source-map/options.json	Remove fixture options file (exec coverage migrated to Jest test).
packages/babel-plugin-transform-modules-commonjs/test/fixtures/source-map/exec.js	Remove fixture exec file (coverage migrated to Jest test).
packages/babel-plugin-transform-block-scoping/test/index.js	Add Jest tests that previously lived as exec fixtures (scope/bindings regressions).
packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10339/exec.js	Remove fixture exec (migrated to Jest test).
packages/babel-plugin-transform-block-scoping/test/fixtures/exec/scope-bindings.js	Remove fixture exec (migrated to Jest test).
packages/babel-plugin-transform-async-generator-functions/test/fixtures/async-generators/await-in-finally/options.json	Add `minNodeVersion` constraint to fixture options.
packages/babel-plugin-proposal-partial-application/test/fixtures/2018-07/member-expression-super/options.json	Add fixture options including `minNodeVersion`.
packages/babel-plugin-proposal-partial-application/test/fixtures/2018-07/member-expression-private-name/options.json	Add fixture options including `minNodeVersion`.
packages/babel-plugin-proposal-decorators/test/fixtures/legacy-object-properties/options.json	Move `targets.node: current` to top-level targets (instead of nested plugin config).
packages/babel-plugin-proposal-decorators/test/fixtures/legacy-object-methods/options.json	Same targets restructuring as above.
packages/babel-plugin-proposal-decorators/test/fixtures/legacy-class-static-properties/options.json	Same targets restructuring as above.
packages/babel-plugin-proposal-decorators/test/fixtures/legacy-class-static-methods/options.json	Same targets restructuring as above.
packages/babel-plugin-proposal-decorators/test/fixtures/legacy-class-prototype-properties/options.json	Same targets restructuring as above.
packages/babel-plugin-proposal-decorators/test/fixtures/legacy-class-prototype-methods/options.json	Same targets restructuring as above.
packages/babel-helpers/test/define-helper.skip-bundled.js	Add dummy test to ensure Jest suite is non-empty when bundled tests are skipped.
packages/babel-helper-transform-fixture-test-runner/test/index.js	Update tests to use the new exported APIs and shared context behavior.
packages/babel-helper-transform-fixture-test-runner/src/worker.cts	Add CommonJS worker implementation used for executing exec tests in isolated context/process.
packages/babel-helper-transform-fixture-test-runner/src/process.ts	Extract/house process-based test runner utilities (previously embedded).
packages/babel-helper-transform-fixture-test-runner/src/index.ts	Switch exec execution to the new worker-backed runner; re-export worker/process helpers.
packages/babel-helper-transform-fixture-test-runner/src/exec.ts	Add logic to run exec tests either in-process or via spawned Node worker (`EXEC_TESTS_NODE`).
packages/babel-helper-transform-fixture-test-runner/package.json	Add deps needed by the worker path (`expect@24` alias, get-node, lru-cache v5 types).
packages/babel-helper-fixtures/src/index.ts	Make fixture minNodeVersion logic consider the configured exec-test node version too.
packages/babel-helper-compilation-targets/package.json	Remove unused devDependencies.
packages/babel-core/test/plugins.js	Migrate various fixture exec tests into explicit Jest tests.
packages/babel-core/test/fixtures/plugins/transform-error/options.json	Remove fixture options file (exec migrated to Jest test).
packages/babel-core/test/fixtures/plugins/transform-error/exec.js	Remove fixture exec file (migrated to Jest test).
packages/babel-core/test/fixtures/plugins/regression-2772/exec.js	Remove fixture exec file (migrated to Jest test).
packages/babel-core/test/fixtures/plugins/nested-if-alternate/exec.js	Remove fixture exec file (migrated to Jest test).
packages/babel-core/test/fixtures/plugins/multiple-definition-evaluation/exec.js	Remove fixture exec file (migrated to Jest test).
packages/babel-core/test/fixtures/plugins/inference-recursion/exec.js	Remove fixture exec file (migrated to Jest test).
packages/babel-core/test/fixtures/plugins/build-code-frame-error/exec.js	Remove fixture exec file (migrated to Jest test).
package.json	Add `get-node-cli` to support prefetching node versions in test setup.
lib/globals.d.ts	Update environment variable typing for breaking-change toggle.
jest.config.ts	Prefetch requested Node version when `EXEC_TESTS_NODE` is set.
Gulpfile.ts	Bundle/build support for the new `.cts` worker entrypoint and adjust CommonJS bundling settings.
.github/workflows/ci.yml	Rename codecov upload label and add a job to run exec tests using Node v6.

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

liuxingbaoyu · 2026-05-28T07:28:02Z

The suggestions provided by copilot were very helpful, and I refactored and fixed it.

liuxingbaoyu · 2026-05-28T08:41:37Z

+              include: [
+                "packages/babel-helper-transform-fixture-test-runner/src/*.cts",
+              ],
+            }),


Perhaps we shouldn't bundle it?
The output is also terrible, including files containing regenerate.

Okay, importing CJS in ESM is cumbersome, so let's stop bundling it.

The bundled lib/index.js on the current main (I am aware that worker.cts is split from index.js in this PR) looks good to me. So this is a new thing specifically in this PR. Could you investigate why regenerate was imported here? Does the new source contain any regexp features that are not widely supported? Or is our build config too conservative on the node.js targets?

babel/Gulpfile.ts

Lines 473 to 485 in 2c05534

dynamicRequireTargets: [

// https://github.com/mathiasbynens/regexpu-core/blob/ffd8fff2e31f4597f6fdfee75d5ac1c5c8111ec3/rewrite-pattern.js#L48

path

.relative(

monorepoRoot,

resolveChain(

import.meta.url,

"./packages/babel-helper-create-regexp-features-plugin",

"regexpu-core",

"regenerate-unicode-properties"

)

)

.replace(/\\/g, "/") + "/**/*.js", // Must be posix path in rollup 3

Because I used dynamic reqiure before, this issue no longer exists.

OK, I thought this one should only be applied to the standalone build task. I am surprised to hear that it will affect the helper-transform-fixture-test-runner as well.

JLHwung · 2026-05-28T13:32:46Z

+import vm = require("vm");
+import LruCache = require("lru-cache");
+import path = require("path");
+import fs = require("fs");


node: prefix should be required here, maybe we should check the linter config.

We did not include .cts in our configuration. :)

liuxingbaoyu force-pushed the exec-worker branch from 05d1543 to d59e4bf Compare August 21, 2025 20:39

liuxingbaoyu force-pushed the exec-worker branch 6 times, most recently from f7a8c25 to 0630f73 Compare September 17, 2025 22:48

nicolo-ribaudo approved these changes Sep 18, 2025

View reviewed changes

liuxingbaoyu force-pushed the exec-worker branch 2 times, most recently from 09eb690 to 0f6d4ed Compare September 18, 2025 18:10

JLHwung reviewed Sep 18, 2025

View reviewed changes

liuxingbaoyu force-pushed the exec-worker branch 3 times, most recently from 6095b2b to 3c40069 Compare September 19, 2025 16:07

liuxingbaoyu force-pushed the exec-worker branch 3 times, most recently from ea73f0c to 017fec7 Compare January 27, 2026 21:56

liuxingbaoyu commented Jan 27, 2026

View reviewed changes

liuxingbaoyu force-pushed the exec-worker branch from 3920e7a to 6f0d568 Compare January 30, 2026 11:59

fisker reviewed Jan 31, 2026

View reviewed changes

liuxingbaoyu force-pushed the exec-worker branch 2 times, most recently from 33060c8 to c30233c Compare March 17, 2026 14:50

liuxingbaoyu force-pushed the exec-worker branch from c30233c to f5fb8ef Compare March 28, 2026 09:38

liuxingbaoyu force-pushed the exec-worker branch from f5fb8ef to b9ec6d6 Compare April 21, 2026 01:37

liuxingbaoyu requested a review from JLHwung April 27, 2026 01:30

liuxingbaoyu mentioned this pull request May 1, 2026

Require Node.js ^22.18.0 || >=24.11.0 #17969

Merged

liuxingbaoyu force-pushed the exec-worker branch from b9ec6d6 to 3535622 Compare May 2, 2026 08:36

liuxingbaoyu force-pushed the exec-worker branch from 83f9251 to 806c258 Compare May 25, 2026 10:54

liuxingbaoyu force-pushed the exec-worker branch 2 times, most recently from 505d00e to 55482db Compare May 26, 2026 12:05

JLHwung requested a review from Copilot May 26, 2026 13:29

Copilot started reviewing on behalf of JLHwung May 26, 2026 13:29 View session

Copilot AI reviewed May 26, 2026

View reviewed changes

liuxingbaoyu force-pushed the exec-worker branch from 55482db to 2ba7e0f Compare May 28, 2026 07:25

liuxingbaoyu force-pushed the exec-worker branch from 2ba7e0f to c267932 Compare May 28, 2026 08:31

liuxingbaoyu commented May 28, 2026

View reviewed changes

liuxingbaoyu force-pushed the exec-worker branch from 85d6a7d to 5973eed Compare May 28, 2026 09:11

JLHwung reviewed May 28, 2026

View reviewed changes

liuxingbaoyu added 3 commits June 23, 2026 16:22

feat

f9817f1

fix

473aa7b

revert

fd7110c

liuxingbaoyu force-pushed the exec-worker branch 2 times, most recently from 82b3b30 to fd7110c Compare June 23, 2026 08:29

rebase

2db29ec

liuxingbaoyu requested a review from JLHwung June 24, 2026 00:40

	dynamicRequireTargets: [
	// https://github.com/mathiasbynens/regexpu-core/blob/ffd8fff2e31f4597f6fdfee75d5ac1c5c8111ec3/rewrite-pattern.js#L48
	path
	.relative(
	monorepoRoot,
	resolveChain(
	import.meta.url,
	"./packages/babel-helper-create-regexp-features-plugin",
	"regexpu-core",
	"regenerate-unicode-properties"
	)
	)
	.replace(/\\/g, "/") + "/*/.js", // Must be posix path in rollup 3

Uh oh!

Uh oh!

Conversation

liuxingbaoyu commented Aug 21, 2025

Uh oh!

babel-bot commented Aug 21, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

pkg-pr-new Bot commented Aug 21, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

nicolo-ribaudo left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

JLHwung Sep 19, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

liuxingbaoyu commented Sep 19, 2025

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

liuxingbaoyu commented May 26, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

liuxingbaoyu commented May 28, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

liuxingbaoyu May 28, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

babel-bot commented Aug 21, 2025 •

edited

Loading

pkg-pr-new Bot commented Aug 21, 2025 •

edited

Loading

JLHwung Sep 19, 2025 •

edited

Loading

liuxingbaoyu commented May 28, 2026 •

edited

Loading

liuxingbaoyu May 28, 2026 •

edited

Loading