fix(loop-init): serialize asset bundling

tools/loop-init/scripts/bundle-assets.mjs

@@ -1,10 +1,11 @@
 #!/usr/bin/env node
-import { cp, rm, access } from 'node:fs/promises';
+import { cp, rm, access, rename, mkdir } from 'node:fs/promises';
 import path from 'node:path';
 import { fileURLToPath } from 'node:url';
 
 const PACKAGE_ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..');
 const REPO_ROOT = path.resolve(PACKAGE_ROOT, '../..');
+const LOCK_DIR = path.join(PACKAGE_ROOT, '.bundle-assets.lock');
 
 async function exists(p) {
   try {
@@ -15,21 +16,71 @@ async function exists(p) {
   }
 }
 
-for (const dir of ['starters', 'templates']) {
-  const dest = path.join(PACKAGE_ROOT, dir);
-  const src = path.join(REPO_ROOT, dir);
-  if (!(await exists(src))) {
-    console.error(`bundle-assets: missing ${src}`);
-    process.exit(1);
+async function replaceDirectory(src, dest) {
+  const tempDest = `${dest}.tmp-${process.pid}-${Date.now()}`;
+  let moved = false;
+  await rm(tempDest, { recursive: true, force: true });
+  try {
+    await cp(src, tempDest, { recursive: true });
+
+    for (let attempt = 0; attempt < 3; attempt += 1) {
+      await rm(dest, { recursive: true, force: true });
+      try {
+        await rename(tempDest, dest);
+        moved = true;
+        return;
+      } catch (err) {
+        if (err?.code !== 'EEXIST' || attempt === 2) {
+          throw err;
+        }
+      }
+    }
+  } finally {
+    if (!moved) {
+      await rm(tempDest, { recursive: true, force: true });
+    }
   }
-  await rm(dest, { recursive: true, force: true });
-  await cp(src, dest, { recursive: true });
-  console.log(`bundled ${dir}/ → tools/loop-init/${dir}/`);
 }
 
-const registrySrc = path.join(REPO_ROOT, 'patterns', 'registry.yaml');
-const registryDest = path.join(PACKAGE_ROOT, 'registry.yaml');
-if (await exists(registrySrc)) {
-  await cp(registrySrc, registryDest);
-  console.log('bundled patterns/registry.yaml → tools/loop-init/registry.yaml');
-}
+async function sleep(ms) {
+  return new Promise((resolve) => {
+    setTimeout(resolve, ms);
+  });
+}
+
+async function acquireLock() {
+  for (let attempt = 0; attempt < 100; attempt += 1) {
+    try {
+      await mkdir(LOCK_DIR);
+      return async () => rm(LOCK_DIR, { recursive: true, force: true });
+    } catch (err) {
+      if (err?.code !== 'EEXIST') {
+        throw err;
+      }
+      await sleep(50);
+    }
+  }
+  throw new Error(`bundle-assets: timed out waiting for ${LOCK_DIR}`);
+}
+
+const releaseLock = await acquireLock();
+try {
+  for (const dir of ['starters', 'templates']) {
+    const dest = path.join(PACKAGE_ROOT, dir);
+    const src = path.join(REPO_ROOT, dir);
+    if (!(await exists(src))) {
+      throw new Error(`bundle-assets: missing ${src}`);
+    }
+    await replaceDirectory(src, dest);
+    console.log(`bundled ${dir}/ → tools/loop-init/${dir}/`);
+  }
+
+  const registrySrc = path.join(REPO_ROOT, 'patterns', 'registry.yaml');
+  const registryDest = path.join(PACKAGE_ROOT, 'registry.yaml');
+  if (await exists(registrySrc)) {
+    await cp(registrySrc, registryDest);
+    console.log('bundled patterns/registry.yaml → tools/loop-init/registry.yaml');
+  }
+} finally {
+  await releaseLock();
+}

tools/loop-init/test/cli.test.mjs

@@ -9,6 +9,16 @@ import { promisify } from 'node:util';
 const exec = promisify(execFile);
 const CLI = path.resolve('dist/cli.js');
 
+test('bundle-assets tolerates concurrent rebuilds', async () => {
+  await Promise.all([
+    exec('node', ['scripts/bundle-assets.mjs']),
+    exec('node', ['scripts/bundle-assets.mjs']),
+  ]);
+  await access(path.join('starters', 'issue-triage', 'README.md'));
+  await access(path.join('templates', 'SKILL.md.issue-triage'));
+  await access('registry.yaml');
+});
+
 test('loop-init --help exits 0', async () => {
   const { stdout } = await exec('node', [CLI, '--help']);
   assert.match(stdout, /changelog-drafter/);
@@ -75,4 +85,4 @@ test('loop-init scaffolds ci-sweeper with bundled assets', async () => {
   } finally {
     await rm(dir, { recursive: true, force: true });
   }
-});
+});