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docs(build-hooks): correct staging-dir cleanup comment

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The previous comment claimed "rmdir-on-non-empty is a no-op" — that is
factually wrong. fs.rmdirSync throws ENOTEMPTY on non-empty directories.
The actual race-safety mechanism is:
1. fs.readdirSync(STAGE_DIR) -> leftovers
2. fs.rmdirSync(STAGE_DIR) only when leftovers.length === 0
3. Outer try/catch swallows TOCTOU ENOTEMPTY (peer added a file
   between readdir and rmdir) and ENOENT (peer already cleaned up).

Comment now references the leftovers variable and both fs calls so a
future reader can map narrative to code without reverse-engineering it.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Tom Boucher
2026-05-06 23:50:52 -04:00
parent c47c2c5def
commit f4c4ec6211
1 changed files with 10 additions and 3 deletions
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13
scripts/build-hooks.js
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@@ -165,14 +165,21 @@ function build() {
} }
// Best-effort cleanup of the staging dir. If concurrent builders are still // Best-effort cleanup of the staging dir. If concurrent builders are still
// running, leftover files belong to them and will be cleaned up on their // running, their staged files will be left in STAGE_DIR and cleaned up by
// own renames; rmdir-on-non-empty is a no-op so this is race-safe. // whichever builder calls fs.rmdirSync last. fs.rmdirSync throws ENOTEMPTY
// on a non-empty directory (it is NOT a silent no-op), so we first read
// the directory via fs.readdirSync(STAGE_DIR) -> leftovers and only call
// fs.rmdirSync(STAGE_DIR) when leftovers.length === 0. A TOCTOU window
// remains: another builder can drop a staged file between the readdirSync
// and the rmdirSync, in which case rmdirSync still throws ENOTEMPTY — the
// outer try/catch swallows that, plus ENOENT if the dir was already
// removed by a peer. Either way, build proceeds; cleanup is best-effort.
try { try {
const leftovers = fs.readdirSync(STAGE_DIR); const leftovers = fs.readdirSync(STAGE_DIR);
if (leftovers.length === 0) { if (leftovers.length === 0) {
fs.rmdirSync(STAGE_DIR); fs.rmdirSync(STAGE_DIR);
} }
} catch (e) { /* tolerate races / missing dir */ } } catch (e) { /* tolerate TOCTOU ENOTEMPTY or ENOENT from peer cleanup */ }
if (hasErrors) { if (hasErrors) {
console.error('\n\x1b[31mBuild failed: fix syntax errors above before publishing.\x1b[0m'); console.error('\n\x1b[31mBuild failed: fix syntax errors above before publishing.\x1b[0m');