bin/dev.mjs: warn on stale webpack watching this checkout#78098
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`npm run dev` produces output via wp-build / esbuild into build/scripts/. A stale webpack dev server still watching this checkout (e.g. left over from a previous setup) can clobber the non-minified index.js files in build/scripts/ with webpack chunk format, breaking the editor when SCRIPT_DEBUG is enabled. Both symptoms are silent — the file just stops being valid JS. This adds a startup check that runs once before `dev()` and logs a clear warning + offending PIDs if it finds webpack processes whose command line or cwd references this checkout's path. The check is deliberately: - Scoped to ROOT_DIR + '/' so unrelated webpack processes from other projects on the same machine don't trigger false positives. - A console.warn, not process.exit, so a misdetection can't block startup. If the file is silently corrupted later, the SCRIPT_DEBUG user will notice; the warning gives them a place to look first. - Best-effort: a `ps aux` failure is swallowed silently. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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mikachan
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May 11, 2026
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mikachan
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This tests well for me, looks good!
A review from Claude suggested changing the warning that mentions kill -9, but I don't think it necessarily needs changing:
kill -9is unnecessarily harsh. The suggested kill command usesSIGKILL, which doesn't give the webpack process a chance to clean up.kill <pids>(SIGTERM) is almost always sufficient for a dev watcher and is more polite. Consider:kill ${ pids.join(' ') }with a note thatkill -9is available as a fallback if it doesn't stop.
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What?
Add a non-fatal startup check to `bin/dev.mjs` that warns if a webpack process is watching this checkout, with the offending PIDs. Best-effort, opt-out by simply not having webpack running.
Why?
`npm run dev` produces output via `wp-build` / esbuild into `build/scripts/`. A stale webpack dev server still watching this checkout (left over from a pre-migration setup, or another package's watcher with overly broad globs) can clobber the non-minified `index.js` files in `build/scripts/` with webpack chunk format. The result is:
This bug bit me while developing #76204 and burned more than a couple of hours figuring out why the bundle on disk wasn't what wp-build said it had emitted. A warning at startup would have caught it immediately.
How?
Adds a single `checkForConflictingProcesses()` function called before `dev()`. It does `ps aux`, filters lines that contain both `webpack` and this repo's path (with a trailing `/` so sibling directories like `/Users/.../gutenberg-fork/` don't false-match), and prints a warning + the matching PIDs + a kill command.
Deliberately:
Testing Instructions
Testing Instructions for Keyboard
N/A — dev tooling only.