fix: harden reproducible checkout races

2026-07-31 18:25:20 -05:00
parent ece7653ca0
commit 0f7061195b
8 changed files with 413 additions and 72 deletions
@@ -0,0 +1,112 @@
+import assert from 'node:assert/strict';
+import { access, mkdir, readFile, rm, writeFile } from 'node:fs/promises';
+import path from 'node:path';
+import test from 'node:test';
+
+import { buildWeb } from './build-web.mjs';
+
+const fixtureRoot = path.join(process.cwd(), '.mosaic-test-work', `build-web-${process.pid}`);
+
+async function fixture(name) {
+  const root = path.join(fixtureRoot, name);
+  await mkdir(path.join(root, 'apps', 'web', '.next'), { recursive: true });
+  return root;
+}
+
+async function exists(target) {
+  try {
+    await access(target);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+test.after(async () => {
+  await rm(fixtureRoot, { recursive: true, force: true });
+});
+
+test('a successful web build atomically publishes its source fingerprint', async () => {
+  const root = await fixture('success');
+  const marker = path.join(root, 'apps', 'web', '.next', '.mosaic-source-hash');
+
+  await buildWeb({ root, fingerprint: async () => 'certified', runBuild: async () => {} });
+
+  assert.equal(await readFile(marker, 'utf8'), 'certified\n');
+});
+
+test('a failed web build leaves no certification marker', async () => {
+  const root = await fixture('failure');
+  const marker = path.join(root, 'apps', 'web', '.next', '.mosaic-source-hash');
+  await writeFile(marker, 'stale\n');
+
+  await assert.rejects(
+    buildWeb({
+      root,
+      fingerprint: async () => 'before',
+      runBuild: async () => {
+        throw new Error('build failed');
+      },
+    }),
+    /build failed/,
+  );
+
+  assert.equal(await exists(marker), false);
+});
+
+test('overlapping web builds are serialized while the marker remains absent', async () => {
+  const root = await fixture('overlap');
+  const marker = path.join(root, 'apps', 'web', '.next', '.mosaic-source-hash');
+  await writeFile(marker, 'stale\n');
+  let releaseFirst;
+  let secondEntered = false;
+  const firstEntered = new Promise((resolve) => {
+    releaseFirst = resolve;
+  });
+  let markFirstEntered;
+  const firstStarted = new Promise((resolve) => {
+    markFirstEntered = resolve;
+  });
+
+  const first = buildWeb({
+    root,
+    fingerprint: async () => 'certified',
+    runBuild: async () => {
+      markFirstEntered();
+      await firstEntered;
+    },
+  });
+  await firstStarted;
+  const second = buildWeb({
+    root,
+    fingerprint: async () => 'certified',
+    runBuild: async () => {
+      secondEntered = true;
+    },
+  });
+  await new Promise((resolve) => setTimeout(resolve, 75));
+  assert.equal(secondEntered, false);
+  assert.equal(await exists(marker), false);
+
+  releaseFirst();
+  await Promise.all([first, second]);
+  assert.equal(secondEntered, true);
+  assert.equal(await readFile(marker, 'utf8'), 'certified\n');
+});
+
+test('inputs changed during a web build are not certified', async () => {
+  const root = await fixture('changed-inputs');
+  const marker = path.join(root, 'apps', 'web', '.next', '.mosaic-source-hash');
+  const fingerprints = ['before', 'after'];
+
+  await assert.rejects(
+    buildWeb({
+      root,
+      fingerprint: async () => fingerprints.shift(),
+      runBuild: async () => {},
+    }),
+    /inputs changed during next build/,
+  );
+
+  assert.equal(await exists(marker), false);
+});