Make build-approved release pending PR workflows

.github/scripts/approve-pr-workflows.cjs

@@ -0,0 +1,78 @@
+const BUILD = '.github/workflows/build-pr.yml';
+const TESTS = '.github/workflows/test.yml';
+
+module.exports = async function approve({ github, context, core, vouchStatus,
+  sleep = ms => new Promise(resolve => setTimeout(resolve, ms)), attempts = 36 }) {
+  // Missing/failed vouch lookups must not become approval. Denouncements
+  // remain absolute, just as they are in the package build gate.
+  if (!['unknown', 'bot', 'collaborator', 'vouched'].includes(vouchStatus)) {
+    throw new Error(`Cannot approve workflows: vouch status is ${vouchStatus || 'missing'}.`);
+  }
+
+  const expected = context.payload.pull_request;
+  const eventTime = Date.parse(expected.updated_at);
+  if (!Number.isFinite(eventTime)) throw new Error('Missing PR event timestamp.');
+  const approved = new Set();
+  let precedingBuild;
+
+  const stillApproved = async () => {
+    const { data: pr } = await github.rest.pulls.get({
+      ...context.repo, pull_number: expected.number,
+    });
+    return pr.state === 'open' && pr.head.sha === expected.head.sha &&
+      pr.labels.some(label => label.name === 'build-approved');
+  };
+
+  // The label and PR-run events arrive independently. Wait for the build
+  // belonging to this event, rather than returning after approving an older
+  // run and leaving the new label-triggered run stuck behind GitHub's gate.
+  for (let attempt = 0; attempt < attempts; attempt++) {
+    if (attempt) await sleep(5000);
+    if (!await stillApproved()) {
+      core.info('PR closed, head changed, or build-approved removed; stopping.');
+      return;
+    }
+
+    const all = await github.paginate(github.rest.actions.listWorkflowRunsForRepo, {
+      ...context.repo, event: 'pull_request', head_sha: expected.head.sha, per_page: 100,
+    });
+    const runs = all.filter(run =>
+      run.event === 'pull_request' && run.head_sha === expected.head.sha &&
+      run.head_repository?.id === expected.head.repo.id && run.head_branch === expected.head.ref &&
+      [BUILD, TESTS].includes(run.path) &&
+      // Fork runs awaiting approval often have no pull_requests entries.
+      (!run.pull_requests?.length || run.pull_requests.some(pr => pr.number === expected.number))
+    ).sort((a, b) => a.id - b.id);
+
+    const newestBuild = runs.findLast(run => run.path === BUILD);
+    if (!newestBuild || !(Date.parse(newestBuild.created_at) >= eventTime) ||
+        !runs.some(run => run.path === TESTS &&
+          (context.payload.action === 'labeled' || Date.parse(run.created_at) >= eventTime))) continue;
+
+    if (precedingBuild) {
+      const { data: run } = await github.rest.actions.getWorkflowRun({
+        ...context.repo, run_id: precedingBuild,
+      });
+      // Approve older builds first, and let them acquire concurrency before
+      // releasing a newer build. Otherwise an older queued run could start
+      // last and cancel the label-triggered build that carries approval.
+      if (!['in_progress', 'completed'].includes(run.status) || run.conclusion === 'action_required') continue;
+      precedingBuild = undefined;
+    }
+
+    const pending = runs.filter(run => run.conclusion === 'action_required' && !approved.has(run.id) &&
+      // If the newest build already runs (e.g. a maintainer approved it),
+      // don't resurrect an obsolete hold that could cancel that newer run.
+      (run.path !== BUILD || run.id === newestBuild.id || newestBuild.conclusion === 'action_required'));
+    if (!pending.length) return;
+    const run = pending[0];
+    // Recheck after the API reads, immediately before exercising write access.
+    if (!await stillApproved()) return;
+    await github.rest.actions.approveWorkflowRun({ ...context.repo, run_id: run.id });
+    approved.add(run.id);
+    core.info(`Approved ${run.path} run ${run.id} for PR #${expected.number}.`);
+    if (run.path === BUILD) precedingBuild = run.id;
+    if (pending.length === 1) return;
+  }
+  throw new Error('Timed out waiting for PR workflows. Remove and reapply build-approved to retry.');
+};