Fix: stop bun run watch infinite rebuild loop (codegen self-trigger)#240
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`build.ts --watch` watches `src/` recursively. Both codegen scripts (`build-site-data`, `build-injection-patterns`) `writeFileSync` their output into `src/rules/*.generated.ts` unconditionally on every build, so each build's write re-triggers the watcher → rebuild → write → loop. The watcher pegs CPU indefinitely, and because builds overlap with no mutex, a newer build's `rm(DIST)` deletes files from under an in-flight one — surfacing as transient `dist/background.js not found` (purity check) and `icons/icon-16.png` ENOENT (cp race). Guard each codegen write with a content comparison so an unchanged output no longer re-arms the watcher. A settled build now stops triggering itself. Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
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Problem
bun run watch(build.ts --watch) spins into an infinite rebuild loop, pegging CPU indefinitely. The symptoms reported were transient build failures:dist/background.js not found — run the extension build first.(background-purity check)ENOENT … copyfile 'icons/icon-16.png' -> 'dist/icons/icon-16.png'(icon copy)These ENOENT errors are symptoms, not real missing files.
Root cause
build.ts --watchwatchessrc/recursively (build.ts:256). Every build runsgenerateSiteData()/generateInjectionPatterns(), whichwriteFileSyncunconditionally intosrc/rules/site-data.generated.tsandsrc/rules/injection-patterns.generated.ts— inside the watched tree. So each build's own write re-triggers the watcher → rebuild → write → loop forever.The watcher also has no build mutex (just a 50ms debounce,
build.ts:251), so builds overlap. Each build starts withawait rm(DIST, …)(build.ts:122), so a newer build deletesdist/out from under an in-flight one — producing the transient "background.js not found" at the purity check and the icon-copy race.Fix
Guard each codegen write with a content comparison (
scripts/file-has-content.ts) so an unchanged output no longer re-arms the watcher. A settled build stops triggering itself, breaking the loop.Verification
bun run builds are clean.bun run checkpasses.bun test scripts/— 37 pass.Note (out of scope)
The missing build mutex is a latent issue: rapid saves during a slow build could still overlap and race on
rm(DIST). This PR removes the self-triggering case, which is what was actually biting. An in-flight guard to serialize concurrent builds could be a follow-up.🤖 Generated with Claude Code