release-label-validation.yaml

name: Validate release labels on PR
on:
  workflow_call:
    inputs:
      on_base_ref:
        required: false
        type: string
        default: main

jobs:
  validate_release_labels:
    name: Run validation
    runs-on: ubuntu-latest
    # This workflow does not work with the Renovate Bot, so it's disabled for those branches
    # It prevents the automerge because the workflow is run for the branch (not PR) and fails
    # This should not be an issue because the Renovate Bot automatically adds the labels
    if: |
      github.event_name == 'pull_request' &&
      github.base_ref == inputs.on_base_ref &&
      contains(fromJSON('["opened", "edited", "synchronize", "reopened", "labeled", "unlabeled"]'), github.event.action) &&
      !startsWith(github.head_ref, 'renovate/')
    steps:
      - uses: actions/setup-python@v5
        with:
          python-version: '3.12'
      - name: determine labels
        id: determine_release_labels
        shell: python
        run: |
          import os
          import json

          allowed_release_labels = ['major', 'minor', 'patch']
          pr_labels = json.loads("""${{ toJSON(github.event.pull_request.labels.*.name) }}""")

          is_chore = 'chore' in pr_labels
          release_labels_on_pr = list(filter(lambda label: label in allowed_release_labels, pr_labels))
          release_labels_count = len(release_labels_on_pr)

          labels_are_valid = release_labels_count == 1 or (release_labels_count == 0 and is_chore)

          GITHUB_OUTPUT = os.getenv('GITHUB_OUTPUT')
          if GITHUB_OUTPUT:
            with open(GITHUB_OUTPUT, 'a') as github_output:
              github_output.write('labels_are_valid={labels_are_valid}\n'.format(labels_are_valid = labels_are_valid))
              github_output.write('release_labels_count={release_labels_count}\n'.format(release_labels_count = release_labels_count))
      - name: fail on empty labels
        if: ${{ steps.determine_release_labels.outputs.labels_are_valid != 'True' && steps.determine_release_labels.outputs.release_labels_count == 0 }}
        run: |
          echo "### :x: a release label (major, minor, patch or chore) must be set" >> $GITHUB_STEP_SUMMARY
          exit 1
      - name: fail on multiple labels
        if: ${{ steps.determine_release_labels.outputs.labels_are_valid != 'True' && steps.determine_release_labels.outputs.release_labels_count > 1 }}
        run: |
          echo "### :x: pr must either be marked as chore or contain exactly one release label (major, minor, patch) " >> $GITHUB_STEP_SUMMARY
          exit 1
      - name: report correct label
        if: steps.determine_release_labels.outputs.labels_are_valid
        run: |
          echo "### :white_check_mark: pr is marked with valid label" >> $GITHUB_STEP_SUMMARY