fix(cli): pass ignore option to chokidar watcher to prevent watching ignored files by sudip-kumar-prasad · Pull Request #17878 · babel/babel

sudip-kumar-prasad · 2026-03-17T18:31:12Z

FFixes #9565 by passing the parsed babel ignore options to chokidar's ignored configuration, preventing system limit errors for wide ignore scopes like node_modules.
Currently, when @babel/cli is run with the --watch flag, chokidar is initialized without knowing which files Babel is configured to ignore. This causes it to unnecessarily track large directories (such as node_modules), potentially leading to ENOSPC file watcher limit errors. This PR ensures that babelOptions.ignore is properly propagated down to chokidar's ignored array.

Fixes babel#9565 by passing the parsed babel ignore options to chokidar's ignored configuration, preventing system limit errors for wide ignore scopes like node_modules.

babel-bot · 2026-03-17T18:33:17Z

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/61285

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Pull request overview

This PR aims to fix @babel/cli --watch watching files that Babel is configured to ignore (e.g. node_modules), reducing the risk of ENOSPC “too many file watchers” errors by passing ignore patterns down to chokidar.

Changes:

Extend watcher.enable to accept an ignore list.
Pass babelOptions.ignore into the chokidar watcher options (ignored) for both file and directory watch modes.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
packages/babel-cli/src/babel/watcher.ts	Adds `ignore` parameter to `enable` and forwards it to chokidar’s `ignored` option.
packages/babel-cli/src/babel/file.ts	Passes `babelOptions.ignore` into watcher setup for `--watch` on file inputs.
packages/babel-cli/src/babel/dir.ts	Passes `babelOptions.ignore` into watcher setup for `--watch` on directory inputs.

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…ignored files

…syntax error

pkg-pr-new · 2026-03-18T13:58:19Z

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commit: 53a1f5d

sudip-kumar-prasad · 2026-03-18T14:03:33Z

Hi 👋 just following up on this PR.

All checks are passing, and I’ve addressed the review feedback.
Would appreciate a review whenever you have time.

Thanks!

JLHwung

Prior to 7.0, Babel-core uses micromatch to handle the ignore option. With #8327, we migrated to a much simpler match patterns.

The chokida 3.4 depended by Babel-cli also implements its own match item: https://github.com/paulmillr/chokidar/blob/c6d772a92f30004fdc437d00ecd54fbed041f30e/src/index.ts#L53.

Could you analyzes any discrepancies between these two and ensure that passing through the ignore option must not lead to uncompiled files? It is acceptable if a file ignored by Babel-core is accepted by chokidar, but it is not acceptable if a compilable file is ignored by chokidar due to different ignore interpretation.

Out of curiosity, did you use LLM to assist opening this PR?

…ignored files

sudip-kumar-prasad · 2026-03-18T20:04:50Z

Thanks for the detailed feedback!

I’ve updated the implementation to rely on loadPartialConfigSync, so the watcher now uses the same ignore logic as Babel core instead of duplicating it.

This ensures that chokidar only ignores files when Babel itself would ignore them (i.e., when it returns null), so there’s no risk of skipping compilable files. It also correctly respects .babelignore and config-based ignore rules.

I’ve also added a small safety fallback so config errors don’t break the watcher.

Regarding your question — yes, I did use AI to assist while working on this, but I verified the changes manually.

Let me know if you’d like me to adjust anything further

sudip-kumar-prasad · 2026-03-20T11:12:29Z

Hi, just a quick follow-up on this.
I’ve addressed the previous feedback and ensured the watcher now uses Babel’s core config via loadPartialConfigSync.

Please let me know if anything else needs adjustment. Thanks!

sudip-kumar-prasad · 2026-03-28T11:48:28Z

I've optimized the watcher by implementing a result cache for the ignored callback. This ensuring loadPartialConfigSync is called only once per unique path during the initial scan/watch session, significantly reducing the overhead on large projects while maintaining full parity with Babel's ignore logic.

sudip-kumar-prasad · 2026-04-02T19:24:45Z

Thanks again for the detailed review!

I took a deeper look into the potential differences between Babel’s ignore handling and chokidar’s pattern matching.

To avoid any discrepancies, the watcher now relies on loadPartialConfigSync to determine whether a file should be ignored. This ensures we only ignore files when Babel itself would skip them (i.e., when it returns null), rather than depending on chokidar’s pattern matching.

Additionally:

Implemented a cache for the ignored callback to avoid repeated config resolution for the same paths
Ensured that even if chokidar’s pattern behavior differs, it won’t exclude files that Babel would compile

This way, we maintain correctness while still reducing unnecessary file watching.

Let me know if you’d like me to add tests specifically covering edge cases around ignore behavior.

…e to support showIgnoredFiles

…-cli-watcher-ignore # Please enter a commit message to explain why this merge is necessary, # especially if it merges an updated upstream into a topic branch. # # Lines starting with '#' will be ignored, and an empty message aborts # the commit.

Rename .babelrc to babel-config.json and move it into in-files/ since the test uses --config-file (project-wide config), not file-relative .babelrc configuration. This aligns the test name and config file with what is actually being tested.

fix(cli): pass ignore option to chokidar watcher (babel#9565)

b702548

Fixes babel#9565 by passing the parsed babel ignore options to chokidar's ignored configuration, preventing system limit errors for wide ignore scopes like node_modules.

Copilot AI review requested due to automatic review settings March 17, 2026 18:31

Copilot started reviewing on behalf of sudip-kumar-prasad March 17, 2026 18:31 View session

Copilot AI reviewed Mar 17, 2026

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Comment thread packages/babel-cli/src/babel/watcher.ts Outdated

Comment thread packages/babel-cli/src/babel/watcher.ts

Comment thread packages/babel-cli/src/babel/file.ts Outdated

Bot added 3 commits March 18, 2026 01:03

fix(cli): pass ignore option to chokidar watcher to prevent watching …

c2cc016

…ignored files

fix(cli): address review feedback for watcher ignore and fix fixture …

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…syntax error

fix(cli): resolve watcher ignore issues, lint errors, and test stability

c877573

JLHwung reviewed Mar 18, 2026

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Comment thread packages/babel-cli/src/babel/watcher.ts Outdated

JLHwung reviewed Mar 18, 2026

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Bot and others added 2 commits March 19, 2026 01:08

fix(cli): pass ignore option to chokidar watcher to prevent watching …

5b61a30

…ignored files

Merge branch 'main' into fix-cli-watcher-ignore

fa79683

JLHwung reviewed Mar 23, 2026

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Comment thread packages/babel-cli/src/babel/watcher.ts

Merge branch 'main' into fix-cli-watcher-ignore

f7daaee

sudip-kumar-prasad requested a review from JLHwung April 1, 2026 12:55

JLHwung reviewed Apr 6, 2026

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Comment thread packages/babel-cli/src/babel/watcher.ts Outdated

Bot added 2 commits April 7, 2026 01:35

fix(cli): pass ignore option to chokidar watcher and update babel-cor…

6f4c5b1

…e to support showIgnoredFiles

JLHwung reviewed Apr 6, 2026

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Comment thread packages/babel-cli/test/fixtures/babel/dir-watch-ignore-config-file/options.json

Bot added 2 commits April 7, 2026 15:40

fix(cli): correctly cache non-ignored results in watcher

53a1f5d

JLHwung mentioned this pull request Apr 7, 2026

fix(register): skip hook for ignored files #17928

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