index.js

// Checks API example
// See: https://developer.github.com/v3/checks/ to learn more

/**
 * This is the main entrypoint to your Probot app
 * @param {import('probot').Application} app
 */
module.exports = app => {
  app.log('Semantic PR Title app loaded!')

  app.on([
    'pull_request.opened',
    'pull_request.reopened',
    'check_run.rerequested',
    'pull_request.edited'
  ], async context => {
    let conclusion = 'failure'
    let message = ''

    context.log.info('context', JSON.stringify(context, null, 2))
    const { payload } = context
    const action = payload.action

    let pr,
      headSha,
      headBranch

    switch (action) {
      case 'rerequested':
        const prs = payload.check_run.check_suite.pull_requests
        pr = prs && prs.length ? prs[0] : null
        headSha = payload.check_run.check_suite.head_sha
        headBranch = payload.check_run.check_suite.head_branch
        break

      case 'reopened':
      case 'edited':
      case 'opened':
        pr = payload.pull_request
        headSha = pr.head.sha
        headBranch = pr.head.ref
        break

      default:
        context.log.info(`action "${action}" not recognized.`)
        break
    }

    // -----------------------------------
    // start the check
    // -----------------------------------
    const check = (await context.github.checks.create(context.repo({
      name: 'Validate Title',
      head_branch: headBranch,
      head_sha: headSha,
      status: 'in_progress',
      started_at: new Date(),
      output: {
        title: 'Checking PR title!',
        summary: 'Let\'s make sure the PR title is valid.'
      }
    }))).data

    const {
      repo,
      owner
    } = await context.repo()

    try {
      if (!pr) {
        throw new Error(`No PRs found for delivery #<a target="_blank" href="https://github.com/settings/apps/semantic-pr-title/advanced#${context.id}">${context.id}</a>.`)
      }

      let { title } = pr

      if (!title) {
        const prQuery = {
          owner,
          repo,
          number: pr.number
        }

        const fullPr = (await context.github.pullRequests.get(prQuery)).data

        if (!fullPr) {
          throw new Error(`Error: could not find pull request for query "${JSON.stringify(prQuery, null, 2)}".`)
        }

        title = fullPr.title
      }

      const config = await context.config('semantic-pr-title.yml', {
        REGEX: '(build|chore|ci|docs|feat|fix|perf|refactor|revert|style|test)(\\([a-z0-9\\s]+\\))?(:\\s)([a-z0-9\\s]+)'
      })

      const regex = new RegExp(config.REGEX, 'i')
      context.log.info(`REGEX is "${config.REGEX}"`)
      message = `PR Title "${title}" does not match regex "${config.REGEX}".`

      if (regex.test(title) === true) {
        conclusion = 'success'
        message = `PR title "${title}" is valid!`
      }

      context.log(`message: ${message}`)
    } catch (err) {
      message = `${err}`
      app.log.error(err)
    }

    // -----------------------------------
    // update check
    // -----------------------------------
    return context.github.checks.update({
      repo,
      owner,
      check_run_id: check.id,
      status: 'completed',
      completed_at: new Date(),
      conclusion,
      output: {
        title: conclusion === 'success' ? 'Check succeeded!' : 'Check failed!',
        summary: message
      }
    })
  })
}