Dangerfile.js

/**
 * @file Dangerfile.js
 * @description Danger rules for pull request hygiene.
 * Runs in CI (GitHub Actions / Vercel preview checks).
 * See https://danger.systems/js/ for full API.
 */
// ── PR description ─────────────────────────────────────────────────────────
if (!danger.github.pr.body || danger.github.pr.body.trim().length < 20) {
  fail('Please add a meaningful PR description (at least 20 characters).')
}
// ── PR size — keep PRs reviewable ──────────────────────────────────────────
const LINES_CHANGED =
  danger.github.pr.additions + danger.github.pr.deletions
if (LINES_CHANGED > 600) {
  warn(
    `This PR changes **${LINES_CHANGED} lines**. Consider splitting it into ` +
    'smaller, focused PRs to make review easier.',
  )
}
// ── Changelog ──────────────────────────────────────────────────────────────
const hasChangelog = danger.git.modified_files.includes('CHANGELOG.md') ||
  danger.git.created_files.includes('CHANGELOG.md')
if (!hasChangelog && LINES_CHANGED > 50) {
  warn('No `CHANGELOG.md` update found. Consider documenting notable changes.')
}
// ── Test coverage — every JS change should have a test ─────────────────────
const changedJsFiles = danger.git.modified_files
  .concat(danger.git.created_files)
  .filter(function isAppJs(f) {
    return f.startsWith('src/js/') && f.endsWith('.js') && !f.endsWith('.test.js')
  })
const changedTestFiles = danger.git.modified_files
  .concat(danger.git.created_files)
  .filter(function isTestFile(f) {
    return f.endsWith('.test.js')
  })
changedJsFiles.forEach(function checkTestCoverage(file) {
  const base = file.replace(/\.js$/, '')
  const hasTest = changedTestFiles.some(function matchesTest(t) {
    return t.includes(base.split('/').pop())
  })
  if (!hasTest) {
    warn(`\`${file}\` was modified but no corresponding test file was updated. ` +
      'Please add or update tests.')
  }
})
// ── No console.log in source ────────────────────────────────────────────────
danger.git.modified_files
  .concat(danger.git.created_files)
  .filter(function isSourceJs(f) {
    return f.startsWith('src/js/') && f.endsWith('.js') && !f.endsWith('.test.js')
  })
  .forEach(async function checkConsoleLog(file) {
    const content = await danger.github.utils.fileContents(file)
    if (content && content.includes('console.log')) {
      warn(`\`${file}\` contains \`console.log\`. Remove before merging.`)
    }
  })
// ── dist/ must be rebuilt if SCSS changed ──────────────────────────────────
const scssChanged = danger.git.modified_files
  .concat(danger.git.created_files)
  .some(function isScss(f) { return f.startsWith('src/scss/') })
const distChanged = danger.git.modified_files
  .concat(danger.git.created_files)
  .some(function isDist(f) { return f.startsWith('dist/') })
if (scssChanged && !distChanged) {
  fail(
    'SCSS files were changed but `dist/styles.css` was not updated. ' +
    'Run `yarn build:scss` and commit the result.',
  )
}
// ── Lockfile consistency ────────────────────────────────────────────────────
const packageChanged = danger.git.modified_files.includes('package.json')
const lockfileChanged = danger.git.modified_files.includes('yarn.lock')
if (packageChanged && !lockfileChanged) {
  warn(
    '`package.json` changed but `yarn.lock` was not updated. ' +
    'Run `yarn install` and commit `yarn.lock`.',
  )
}
// ── No direct pushes to main ────────────────────────────────────────────────
if (danger.github.pr.base.ref === 'main' &&
    danger.github.pr.head.ref === 'main') {
  fail('Direct pushes to `main` are not allowed. Please use a feature branch.')
}
// ── Summary ─────────────────────────────────────────────────────────────────
message(
  `📊 **PR stats:** +${danger.github.pr.additions} / -${danger.github.pr.deletions} lines ` +
  `across ${danger.github.pr.changed_files} file(s).`,
)
// ── Conventional commit format on PR title ─────────────────────────────────
// semantic-release reads commit messages — squash-merge PRs use the PR title
// as the commit message, so it must follow Conventional Commits format.
const CONVENTIONAL_PATTERN =
  /^(feat|fix|docs|style|refactor|perf|test|chore|ci|build|revert)(\(.+\))?!?: .{1,100}$/
if (!CONVENTIONAL_PATTERN.test(danger.github.pr.title)) {
  fail(
    `PR title \`${danger.github.pr.title}\` does not follow ` +
    '[Conventional Commits](https://www.conventionalcommits.org/) format.\n\n' +
    'Expected: `type(scope): description`\n' +
    'e.g. `feat: add reverb section` or `fix(tooltip): clamp on narrow screens`\n\n' +
    'The PR title becomes the squash-merge commit message that\n' +
    '**semantic-release** uses to determine the version bump.',
  )
}