Add workflow to insert PR preview links

.github/scripts/add-preview-links.mjs

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+import fs from 'fs/promises';
+import { pathToFileURL } from 'url';
+
+export const START_MARKER = '<!-- profiler-preview-links:start -->';
+export const END_MARKER = '<!-- profiler-preview-links:end -->';
+
+const GITHUB_API_URL = 'https://api.github.com';
+const GITHUB_API_VERSION = '2026-03-10';
+const MAIN_BASE_URL = 'https://main--perf-html.netlify.app';
+const PROFILE_HOST = 'profiler.firefox.com';
+const SHARE_HOST = 'share.firefox.dev';
+
+export function hasDeployPreviewLink(body) {
+  return (
+    body.includes(START_MARKER) ||
+    /https:\/\/deploy-preview-\d+--perf-html\.netlify\.app(?:\/|\b)/.test(body)
+  );
+}
+
+export function extractIssueNumbers(text) {
+  const issueNumbers = new Set();
+  const markdownIssueRegExp = /(?:^|[^\w/-])#(\d+)\b/g;
+  const issueUrlRegExp =
+    /https:\/\/github\.com\/firefox-devtools\/profiler\/issues\/(\d+)\b/g;
+
+  for (const match of text.matchAll(markdownIssueRegExp)) {
+    issueNumbers.add(Number(match[1]));
+  }
+
+  for (const match of text.matchAll(issueUrlRegExp)) {
+    issueNumbers.add(Number(match[1]));
+  }
+
+  return [...issueNumbers];
+}
+
+export function extractProfileUrls(text) {
+  const urls = [];
+  const profileUrlRegExp =
+    /https:\/\/(?:share\.firefox\.dev|profiler\.firefox\.com)\/[^\s<>)\]]+/g;
+
+  for (const match of text.matchAll(profileUrlRegExp)) {
+    // Profile links are often followed by punctuation in prose, for example
+    // "Profile: https://share.firefox.dev/466MJwC.".
+    urls.push(match[0].replace(/[.,;:]+$/, ''));
+  }
+
+  return urls;
+}
+
+export function profileUrlToPath(profileUrl) {
+  const url = new URL(profileUrl);
+
+  if (url.hostname !== PROFILE_HOST) {
+    return null;
+  }
+
+  const path = `${url.pathname}${url.search}${url.hash}`;
+  return path === '/' ? null : path;
+}
+
+// Returns the path for a profiler.firefox.com URL, and follows share.firefox.dev
+// redirects to resolve short links to their full profiler.firefox.com URL.
+export async function resolveProfileUrlToPath(profileUrl, fetchImpl = fetch) {
+  const url = new URL(profileUrl);
+
+  if (url.hostname === PROFILE_HOST) {
+    return profileUrlToPath(profileUrl);
+  }
+
+  if (url.hostname !== SHARE_HOST) {
+    return null;
+  }
+
+  const response = await fetchImpl(profileUrl, { redirect: 'follow' });
+  return profileUrlToPath(response.url);
+}
+
+export function normalizePath(path) {
+  if (!path || path === '/') {
+    return '/';
+  }
+
+  return path.startsWith('/') ? path : `/${path}`;
+}
+
+export function buildPreviewLinks(prNumber, path) {
+  const normalizedPath = normalizePath(path);
+  const previewBaseUrl = `https://deploy-preview-${prNumber}--perf-html.netlify.app`;
+
+  return `[Main](${MAIN_BASE_URL}${normalizedPath}) | [Deploy preview](${previewBaseUrl}${normalizedPath})`;
+}
+
+export function addPreviewLinksToBody(body, previewLinks) {
+  const previewLinksBlock = `${START_MARKER}\n${previewLinks}\n${END_MARKER}`;
+  const trimmedBody = body.trim();
+
+  if (!trimmedBody) {
+    return previewLinksBlock;
+  }
+
+  return `${previewLinksBlock}\n\n${trimmedBody}`;
+}
+
+async function githubRequest(path, token, options = {}) {
+  const response = await fetch(`${GITHUB_API_URL}${path}`, {
+    ...options,
+    headers: {
+      accept: 'application/vnd.github+json',
+      authorization: `Bearer ${token}`,
+      'content-type': 'application/json',
+      'user-agent': 'firefox-profiler-preview-links',
+      'x-github-api-version': GITHUB_API_VERSION,
+      ...options.headers,
+    },
+  });
+
+  if (!response.ok) {
+    const message = await response.text();
+    throw new Error(
+      `GitHub API request failed: ${response.status} ${response.statusText}\n${message}`
+    );
+  }
+
+  if (response.status === 204) {
+    return null;
+  }
+
+  return response.json();
+}
+
+async function getIssueTexts({ owner, repo, issueNumber, token }) {
+  const issue = await githubRequest(
+    `/repos/${owner}/${repo}/issues/${issueNumber}`,
+    token
+  );
+  const comments = await githubRequest(
+    `/repos/${owner}/${repo}/issues/${issueNumber}/comments?per_page=100`,
+    token
+  );
+
+  return [issue.body ?? '', ...comments.map((comment) => comment.body ?? '')];
+}
+
+async function getPullRequest({ owner, repo, pullNumber, token }) {
+  return githubRequest(`/repos/${owner}/${repo}/pulls/${pullNumber}`, token);
+}
+
+// Finds the first profile path mentioned in the PR or its linked issues.
+// Returns '/' if no profile link is found, so generated links use the homepage.
+async function findProfilePath({ owner, repo, pullRequest, token }) {
+  const pullRequestText = `${pullRequest.title ?? ''}\n${pullRequest.body ?? ''}`;
+
+  for (const profileUrl of extractProfileUrls(pullRequestText)) {
+    const path = await resolveProfileUrlToPath(profileUrl);
+
+    if (path) {
+      return path;
+    }
+  }
+
+  for (const issueNumber of extractIssueNumbers(pullRequestText)) {
+    let issueTexts;
+
+    try {
+      issueTexts = await getIssueTexts({ owner, repo, issueNumber, token });
+    } catch (error) {
+      console.warn(`Could not read issue #${issueNumber}: ${error.message}`);
+      continue;
+    }
+
+    for (const issueText of issueTexts) {
+      for (const profileUrl of extractProfileUrls(issueText)) {
+        const path = await resolveProfileUrlToPath(profileUrl);
+
+        if (path) {
+          return path;
+        }
+      }
+    }
+  }
+
+  return '/';
+}
+
+export async function main() {
+  const eventPath = process.env.GITHUB_EVENT_PATH;
+  const repository = process.env.GITHUB_REPOSITORY;
+  const token = process.env.GITHUB_TOKEN;
+
+  if (!eventPath || !repository || !token) {
+    throw new Error(
+      'GITHUB_EVENT_PATH, GITHUB_REPOSITORY, and GITHUB_TOKEN are required.'
+    );
+  }
+
+  const payload = JSON.parse(await fs.readFile(eventPath, 'utf8'));
+  const pullRequest = payload.pull_request;
+
+  if (!pullRequest) {
+    console.log('This event does not include a pull request. Nothing to do.');
+    return;
+  }
+
+  const [owner, repo] = repository.split('/');
+  const body = pullRequest.body ?? '';
+
+  if (hasDeployPreviewLink(body)) {
+    console.log('The pull request already has deploy preview links.');
+    return;
+  }
+
+  const profilePath = await findProfilePath({
+    owner,
+    repo,
+    pullRequest,
+    token,
+  });
+  const previewLinks = buildPreviewLinks(pullRequest.number, profilePath);
+
+  // Re-read the PR body just before patching it. GitHub's API does not support
+  // conditional PATCH requests here, so this is a best-effort guard against
+  // overwriting edits that happened while this script looked up the profile URL.
+  const latestPullRequest = await getPullRequest({
+    owner,
+    repo,
+    pullNumber: pullRequest.number,
+    token,
+  });
+  const latestBody = latestPullRequest.body ?? '';
+
+  if (hasDeployPreviewLink(latestBody)) {
+    console.log('The pull request already has deploy preview links.');
+    return;
+  }
+
+  const updatedBody = addPreviewLinksToBody(latestBody, previewLinks);
+
+  await githubRequest(
+    `/repos/${owner}/${repo}/pulls/${pullRequest.number}`,
+    token,
+    {
+      body: JSON.stringify({ body: updatedBody }),
+      method: 'PATCH',
+    }
+  );
+
+  console.log(`Added preview links to pull request #${pullRequest.number}.`);
+}
+
+if (
+  process.argv[1] &&
+  import.meta.url === pathToFileURL(process.argv[1]).href
+) {
+  await main();
+}

.github/scripts/add-preview-links.test.mjs

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+import assert from 'assert/strict';
+import { test } from 'node:test';
+
+import {
+  END_MARKER,
+  START_MARKER,
+  addPreviewLinksToBody,
+  buildPreviewLinks,
+  extractIssueNumbers,
+  extractProfileUrls,
+  hasDeployPreviewLink,
+  normalizePath,
+  profileUrlToPath,
+  resolveProfileUrlToPath,
+} from './add-preview-links.mjs';
+
+test('hasDeployPreviewLink detects generated and manual preview links', () => {
+  assert.equal(hasDeployPreviewLink('No preview links here.'), false);
+  assert.equal(
+    hasDeployPreviewLink(
+      '[Deploy preview](https://deploy-preview-6083--perf-html.netlify.app/)'
+    ),
+    true
+  );
+  assert.equal(
+    hasDeployPreviewLink(`${START_MARKER}\nlinks\n${END_MARKER}`),
+    true
+  );
+});
+
+test('extractIssueNumbers finds markdown references and issue URLs', () => {
+  assert.deepEqual(
+    extractIssueNumbers(
+      'Fixes #5598 and see https://github.com/firefox-devtools/profiler/issues/6083. Duplicate #5598.'
+    ),
+    [5598, 6083]
+  );
+});
+
+test('extractProfileUrls finds profiler and share URLs', () => {
+  assert.deepEqual(
+    extractProfileUrls('Profile: https://share.firefox.dev/466MJwC.'),
+    ['https://share.firefox.dev/466MJwC']
+  );
+  assert.deepEqual(
+    extractProfileUrls(
+      '[Profile](https://profiler.firefox.com/public/abc/calltree/?thread=1&v=16)'
+    ),
+    ['https://profiler.firefox.com/public/abc/calltree/?thread=1&v=16']
+  );
+});
+
+test('profileUrlToPath keeps the profiler path, query, and hash', () => {
+  assert.equal(
+    profileUrlToPath(
+      'https://profiler.firefox.com/public/abc/flame-graph/?thread=1&v=16#hash'
+    ),
+    '/public/abc/flame-graph/?thread=1&v=16#hash'
+  );
+  assert.equal(profileUrlToPath('https://profiler.firefox.com/'), null);
+});
+
+test('resolveProfileUrlToPath follows share.firefox.dev redirects', async () => {
+  const fetchImpl = async () => ({
+    url: 'https://profiler.firefox.com/public/abc/marker-table/?thread=0&v=16',
+  });
+
+  assert.equal(
+    await resolveProfileUrlToPath(
+      'https://share.firefox.dev/466MJwC',
+      fetchImpl
+    ),
+    '/public/abc/marker-table/?thread=0&v=16'
+  );
+});
+
+test('buildPreviewLinks uses the main branch and deploy preview hosts', () => {
+  assert.equal(normalizePath('public/abc'), '/public/abc');
+  assert.equal(
+    buildPreviewLinks(6083, '/public/abc/marker-table/?thread=0&v=16'),
+    '[Main](https://main--perf-html.netlify.app/public/abc/marker-table/?thread=0&v=16) | [Deploy preview](https://deploy-preview-6083--perf-html.netlify.app/public/abc/marker-table/?thread=0&v=16)'
+  );
+});
+
+test('addPreviewLinksToBody prepends a marked block', () => {
+  assert.equal(
+    addPreviewLinksToBody(
+      'Fixes #5598.',
+      '[Main](main) | [Deploy preview](preview)'
+    ),
+    `${START_MARKER}\n[Main](main) | [Deploy preview](preview)\n${END_MARKER}\n\nFixes #5598.`
+  );
+});

.github/workflows/add-preview-links.yml

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+name: Add preview links
+
+on:
+  pull_request_target:
+    types:
+      - opened
+      - edited
+      - reopened
+      - ready_for_review
+
+permissions:
+  contents: read
+  issues: read
+  pull-requests: write
+
+concurrency:
+  group: add-preview-links-${{ github.event.pull_request.number }}
+  cancel-in-progress: false
+
+jobs:
+  add-preview-links:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v5
+        with:
+          persist-credentials: false
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v6
+        with:
+          node-version: '24'
+
+      - name: Add preview links
+        run: node .github/scripts/add-preview-links.mjs
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}