add-milestone-to-pull-requests.yaml

name: Add milestone to pull requests
on:
  pull_request:
    types: [closed]
    branches:
      - master
      - release/v*
jobs:
  add_milestone_to_merged:
    name: Add milestone to merged pull requests
    permissions:
      issues: write # Required to update a pull request using the issues API
      pull-requests: write # Required to update the milestone of a pull request
    if: github.event.pull_request.merged && github.event.pull_request.milestone == null
    runs-on: ubuntu-latest
    steps:
      - name: Add milestone to merged pull requests
        uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea # 7.0.1
        with:
          script: |
            // Get project milestones
            const response = await github.rest.issues.listMilestones({
              owner: context.repo.owner,
              repo: context.repo.repo,
              state: 'open'
            })
            if (!response.data || response.data.length == 0) {
              core.setFailed(`Failed to list milestones: ${response.status}`)
              return
            }
            // Get the base branch
            const base = '${{ github.event.pull_request.base.ref }}'
            // Look for the matching milestone
            let milestoneNumber = null
            if (base == 'master') {
              // Pick the milestone with the highest version as title using semver
              milestoneNumber = response.data
                .map(milestone => {
                  // Parse version title as semver "<major>.<minor>.<patch>"
                  const versionNumbers = milestone.title.match(/^(\d+)\.(\d+)\.(\d+)$/)
                  if (versionNumbers == null) {
                    return null
                  }
                  milestone.version = {
                    major: parseInt(versionNumbers[1]),
                    minor: parseInt(versionNumbers[2]),
                    patch: parseInt(versionNumbers[3])
                  }
                  return milestone
                })
                .filter(milestone => milestone != null)
                .sort((a, b) => {
                  if (a.version.major != b.version.major) {
                    return a.version.major - b.version.major
                  }
                  if (a.version.minor != b.version.minor) {
                    return a.version.minor - b.version.minor
                  }
                  return a.version.patch - b.version.patch
                })
                .pop()?.number
            } else if (base.startsWith('release/v') && base.endsWith('.x')) {
              // Extract the minor version related to the base branch (e.g. "release/v1.2.x" -> "1.2.")
              const version = base.substring(9, base.length - 1)
              // Pick the milestone with title matching the extracted version
              const versionMilestone = response.data
                .find(milestone => milestone.title.startsWith(version))
              if (!versionMilestone) {
                core.setFailed(`Milestone not found for minor version: ${version}`)
              } else {
                milestoneNumber = versionMilestone.number
              }
            } else {
              core.setFailed(`Unexpected pull request base: ${base}`)
            }
            // Update pull request milestone using the issues API (as pull requests are issues)
            if (milestoneNumber != null) {
              await github.rest.issues.update({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: ${{ github.event.pull_request.number }},
                milestone: milestoneNumber
              });
            }