draft-release-notes-on-tag.yaml

name: Draft release notes on tag
on:
  create:
  workflow_dispatch:

jobs:
  draft_release_notes:
    name: Draft release notes
    if: (github.event.ref_type == 'tag' && github.event.master_branch == 'master') || github.event_name == 'workflow_dispatch'
    runs-on: ubuntu-latest
    steps:
      - name: Get milestone title
        id: milestoneTitle
        uses: actions/github-script@d7906e4ad0b1822421a7e6a35d5ca353c962f410 # 6.4.1
        with:
          result-encoding: string
          script: |
            // Get the milestone title ("X.Y.Z") from tag name ("vX.Y.Z(-rc)")
            const match = '${{github.event.ref}}'.match(/v(\d+\.\d+\.\d+)(?:-rc\d+)?/i)
            if (!match) {
              core.setFailed('Failed to parse tag name into milestone name: ${{github.event.ref}}')
              return
            }
            const milestoneTitle = match[1]

            // Look for the milestone
            const milestone = (await github.paginate('GET /repos/{owner}/{repo}/milestones', {
              owner: context.repo.owner,
              repo: context.repo.repo,
              state: 'all'
            })).find(m => m.title == milestoneTitle)
            if (!milestone) {
              core.setFailed(`Failed to find milestone: ${milestoneTitle}`)
              return
            }

            // Get pull requests of the milestone
            const pullRequests = (await github.paginate('/repos/{owner}/{repo}/issues', {
              owner: context.repo.owner,
              repo: context.repo.repo,
              milestone: milestone.number,
              state: 'closed'
            }))
            .filter(i => i.pull_request && i.pull_request.merged_at)                     // Skip closed but not merged
            .filter(p => !p.labels.find(label => label.name == 'tag: no release notes')) // Skip excluded

            // Group PR by components and instrumentations
            var prByComponents = new Map()
            var prByInstrumentations = new Map()
            var otherPRs = new Array()
            for (let pullRequest of pullRequests) {
              var captured = false
              for (let label of pullRequest.labels) {
                const index = label.name.indexOf(':')
                if (index == -1) {
                  core.notice('Unsupported label: ${label.name}')
                  continue
                }
                const labelKey = label.name.substring(0, index)
                const labelValue = label.name.slice(index + 1)
                var map = null
                if (labelKey == 'comp') {
                  map = prByComponents
                } else if (labelKey == 'inst') {
                  map = prByInstrumentations
                }
                if (map) {
                  var prs = map.get(label.description)
                  if (!prs) {
                    prs = new Array()
                    map.set(label.description, prs)
                  }
                  prs.push(pullRequest)
                  captured = true
                }
              }
              if (!captured) {
                otherPRs.push(pullRequest)
              }
            }

            // Sort components and instrumenations
            prByComponents = new Map([...prByComponents].sort());
            const lastInstrumentation = 'All other instrumentations'
            prByInstrumentations = new Map([...prByInstrumentations].sort(
              (a, b) => {
                if (a[0] == lastInstrumentation) {
                  return 1
                } else if (b[0] == lastInstrumentation) {
                  return -1
                }
                return String(a[0]).localeCompare(b[0])
              }
            ));

            // Generate changelog
            const decorators = {
              'tag: breaking change': ':warning:',
              'tag: experimental': ':test_tube:',
              'tag: diagnostics': ':mag:',
              'tag: performance': ':zap:',
              'tag: security': ':closed_lock_with_key:',
              'type: bug': ':bug:',
              'type: documentation': ':book:',
              'type: enhancement': ':sparkles:',
              'type: feature request': ':bulb:',
              'type: refactoring': ':broom:'
            }
            function decorate(pullRequest) {
              var line = ''
              var decorated = false;
              for (let label of pullRequest.labels) {
                if (decorators[label.name]) {
                  line += decorators[label.name]
                  decorated = true
                }
              }
              if (decorated) {
                line += ' '
              }
              return line
            }
            function cleanUpTitle(title) {
              // Remove tags between brackets
              return title.replace(/\[[^\]]+\]/g, '')
            }
            function format(pullRequest) {
              var line = `${decorate(pullRequest)}${cleanUpTitle(pullRequest.title)} (#${pullRequest.number} - @${pullRequest.user.login}`
              // Add special thanks if community labeled
              if (pullRequest.labels.some(label => label.name == "tag: community")) {
                line += ` - thanks for the contribution!`
              }
              line += ')'
              return line;
            }

            var changelog = ''
            if ('${{github.event.ref}}'.match(/rc/i)) {
              changelog += ':warning:  This is a RELEASE CANDIDATE and is NOT intended for use in production. Please contact Datadog support regarding any problems in this RC.\n'
            }
            if (prByComponents.size > 0) {
              changelog += '# Components\n\n';
              for (let pair of prByComponents) {
                changelog += '## '+pair[0]+'\n\n'
                for (let pullRequest of pair[1]) {
                  changelog += '* ' + format(pullRequest) + '\n'
                }
                changelog += '\n'
              }
            }
            if (prByInstrumentations.size > 0) {
              changelog += '# Instrumentations\n\n'
              for (let pair of prByInstrumentations) {
                changelog += '## '+pair[0]+'\n\n'
                for (let pullRequest of pair[1]) {
                  changelog += '* ' + format(pullRequest) + '\n'
                }
                changelog += '\n'
              }
            }
            if (otherPRs.length > 0) {
              changelog += '# Other changes\n\n'
              for (let pullRequest of otherPRs) {
                changelog += '* ' + format(pullRequest) + '\n'
              }
            }

            // Create release with the draft changelog
            await github.rest.repos.createRelease({
              owner: context.repo.owner,
              repo: context.repo.repo,
              tag_name: '${{ github.event.ref }}',
              name: milestoneTitle,
              draft: true,
              body: changelog
            })