ci: sync PR labels from the conventional-commit title (#37784)

Syncs `type/*` and `pr/breaking` labels from the PR title (Conventional
Commits) and folds the existing title lint into the same workflow so
labeling only runs once the title is valid.

- `tools/pr-title.ts`: shared title parser and label mapping.
- `tools/set-pr-labels.ts`: adds/removes labels via the GitHub API.
`type/*` and `pr/breaking` are fully synced (added and removed);
`skip-changelog` (chore/ci) and `topic/build` (build) are only added,
never auto-removed, so manual labeling is preserved.
- `pull-labeler.yml` now hosts `lint-pr-title` and `set-pr-labels`
(`needs: lint-pr-title`) under `pull_request_target`, required so fork
PRs get a writable token. Base-branch checkout only; no PR-head code
runs in the elevated context.
- Removes the superseded `pull-pr-title.yml` and the CI-only
`lint-pr-title` Makefile target.

---------

Signed-off-by: silverwind <me@silverwind.io>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: TheFox0x7 <thefox0x7@gmail.com>

.github/workflows/pull-labeler.yml

@@ -1,8 +1,10 @@
 name: labeler
 
 on:
-  pull_request_target:
-    types: [opened, synchronize, reopened]
+  # pull_request_target is required to label PRs from forks; jobs only use pinned
+  # actions or base-branch checkout, never PR-head code.
+  pull_request_target: # zizmor: ignore[dangerous-triggers]
+    types: [opened, synchronize, reopened, edited, ready_for_review]
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
@@ -18,3 +20,28 @@ jobs:
       - uses: actions/labeler@f27b608878404679385c85cfa523b85ccb86e213 # v6.1.0
         with:
           sync-labels: true
+
+  pr-title:
+    if: github.event.pull_request.draft == false
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    permissions:
+      contents: read
+      issues: write
+    steps:
+      # Base-branch checkout only: pull_request_target runs with elevated token; never run PR-head code here.
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          ref: ${{ github.event.pull_request.base.sha }}
+      - uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0
+        with:
+          node-version: 24
+      # Labels are only synced after the title lints, so an invalid title never reaches the label diff.
+      - run: node ./tools/ci-tools.ts lint-pr-title
+        env:
+          PR_TITLE: ${{ github.event.pull_request.title }}
+      - run: node ./tools/ci-tools.ts set-pr-labels
+        env:
+          PR_TITLE: ${{ github.event.pull_request.title }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+          GITHUB_TOKEN: ${{ github.token }}

.github/workflows/pull-pr-title.yml

@@ -1,31 +0,0 @@
-name: pr-title
-
-on:
-  pull_request:
-    types:
-      - opened
-      - edited
-      - reopened
-      - synchronize
-      - ready_for_review
-
-concurrency:
-  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
-  cancel-in-progress: true
-
-permissions:
-  contents: read
-
-jobs:
-  lint-pr-title:
-    if: github.event.pull_request.draft == false
-    runs-on: ubuntu-latest
-    timeout-minutes: 5
-    steps:
-      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
-      - uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0
-        with:
-          node-version: 24
-      - run: make lint-pr-title
-        env:
-          PR_TITLE: ${{ github.event.pull_request.title }}

Makefile

@@ -321,10 +321,6 @@ lint-md: node_modules ## lint markdown files
 lint-md-fix: node_modules ## lint markdown files and fix issues
 	pnpm exec markdownlint --fix *.md
 
-.PHONY: lint-pr-title
-lint-pr-title: ## lint PR title against Conventional Commits (set PR_TITLE=...)
-	@node ./tools/lint-pr-title.ts
-
 .PHONY: lint-spell
 lint-spell: ## lint spelling
 	@git ls-files $(SPELLCHECK_FILES) | xargs go run $(MISSPELL_PACKAGE) -dict assets/misspellings.csv -error

tools/ci-tools.ts

@@ -0,0 +1,133 @@
+#!/usr/bin/env node
+import {argv, env, exit} from 'node:process';
+
+const allowedTypes = [
+  'build',
+  'chore',
+  'ci',
+  'docs',
+  'enhance',
+  'feat',
+  'fix',
+  'perf',
+  'refactor',
+  'revert',
+  'style',
+  'test',
+] as const;
+type CommitType = typeof allowedTypes[number];
+
+const allowedTypesList = allowedTypes.join(', ');
+const titlePattern = new RegExp(`^(${allowedTypes.join('|')})(\\([\\w/.-]+\\))?(!)?: .+$`);
+
+function parsePrTitle(title: string): {type: CommitType; breaking: boolean} | null {
+  const match = titlePattern.exec(title);
+  return match ? {type: match[1] as CommitType, breaking: Boolean(match[3])} : null;
+}
+
+const breakingLabel = 'pr/breaking';
+
+// Mutually exclusive type labels, fully synced with the title type (added and removed).
+const typeLabels: Partial<Record<CommitType, string>> = {
+  feat: 'type/feature',
+  enhance: 'type/enhancement',
+  fix: 'type/bug',
+  docs: 'type/docs',
+  test: 'type/testing',
+};
+
+// Non-type labels, only added, never auto-removed, so manual labeling is not clobbered.
+const extraLabels: Partial<Record<CommitType, string>> = {
+  chore: 'skip-changelog',
+  ci: 'skip-changelog',
+  build: 'topic/build',
+};
+
+// Labels this tool may remove when the title no longer implies them.
+const removableLabels = [...Object.values(typeLabels), breakingLabel];
+
+function labelsForPrTitle(title: string): string[] {
+  const parsed = parsePrTitle(title);
+  if (!parsed) return [];
+  return [typeLabels[parsed.type], extraLabels[parsed.type], parsed.breaking ? breakingLabel : undefined]
+    .filter((label): label is string => label !== undefined);
+}
+
+// Command: validate PR_TITLE against the allowed Conventional Commits format.
+function lintPrTitle(): void {
+  if (!env.PR_TITLE) {
+    console.error('Missing PR_TITLE');
+    exit(1);
+  }
+  if (!parsePrTitle(env.PR_TITLE)) {
+    console.error(`Invalid PR title: ${env.PR_TITLE}`);
+    console.error('Expected format: type(scope): subject (scope optional, append "!" for breaking changes)');
+    console.error(`Allowed types: ${allowedTypesList}`);
+    exit(1);
+  }
+}
+
+// Command: sync the title-derived labels onto the PR via the GitHub API.
+async function setPrLabels(): Promise<void> {
+  if (!env.PR_TITLE || !env.GITHUB_TOKEN || !env.GITHUB_REPOSITORY || !env.PR_NUMBER) {
+    console.error('set-pr-labels requires PR_TITLE, GITHUB_TOKEN, GITHUB_REPOSITORY and PR_NUMBER');
+    exit(1);
+  }
+
+  const labelsUrl = `https://api.github.com/repos/${env.GITHUB_REPOSITORY}/issues/${env.PR_NUMBER}/labels`;
+
+  async function request(url: string, method = 'GET', body?: unknown): Promise<Response> {
+    const response = await fetch(url, {
+      method,
+      headers: {
+        Accept: 'application/vnd.github+json',
+        Authorization: `Bearer ${env.GITHUB_TOKEN}`,
+        'X-GitHub-Api-Version': '2022-11-28',
+        ...(body ? {'Content-Type': 'application/json'} : {}),
+      },
+      body: body ? JSON.stringify(body) : undefined,
+    });
+    if (!response.ok) {
+      throw new Error(`GitHub API ${method} ${url} failed (${response.status}): ${await response.text()}`);
+    }
+    return response;
+  }
+
+  const desired = labelsForPrTitle(env.PR_TITLE);
+  const response = await request(`${labelsUrl}?per_page=100`);
+  const current = ((await response.json()) as Array<{name: string}>).map((label) => label.name);
+
+  const toAdd = desired.filter((name) => !current.includes(name));
+  const toRemove = removableLabels.filter((name) => current.includes(name) && !desired.includes(name));
+
+  if (toAdd.length) {
+    await request(labelsUrl, 'POST', {labels: toAdd});
+    console.info(`Added labels: ${toAdd.join(', ')}`);
+  }
+  for (const name of toRemove) {
+    await request(`${labelsUrl}/${encodeURIComponent(name)}`, 'DELETE');
+    console.info(`Removed label: ${name}`);
+  }
+  if (!toAdd.length && !toRemove.length) {
+    console.info('PR labels already in sync');
+  }
+}
+
+const commands: Record<string, () => void | Promise<void>> = {
+  'lint-pr-title': lintPrTitle,
+  'set-pr-labels': setPrLabels,
+};
+
+const command = argv[2];
+const handler = commands[command];
+if (!handler) {
+  console.error(`Usage: ci-tools.ts <${Object.keys(commands).join('|')}>`);
+  exit(1);
+}
+
+try {
+  await handler();
+} catch (error) {
+  console.error(error instanceof Error ? error.message : error);
+  exit(1);
+}

tools/lint-pr-title.ts

@@ -1,19 +0,0 @@
-#!/usr/bin/env node
-import {env, exit} from 'node:process';
-
-const allowedTypes = 'build, chore, ci, docs, enhance, feat, fix, perf, refactor, revert, style, test';
-const title = env.PR_TITLE;
-
-if (!title) {
-  console.error('Missing PR_TITLE');
-  exit(1);
-}
-
-const validTitlePattern = new RegExp(`^(${allowedTypes.replaceAll(', ', '|')})(\\([\\w.-]+\\))?(!)?: .+$`);
-
-if (!validTitlePattern.test(title)) {
-  console.error(`Invalid PR title: ${title}`);
-  console.error('Expected format: type(scope): subject');
-  console.error(`Allowed types: ${allowedTypes}`);
-  exit(1);
-}