.github/workflows/pr-comment.yml

name: pr-comment

on:
  # Runs once when the 'pr' workflow is requested, and again when it's completed
  workflow_run:
    workflows:
      - pr
    types:
      - requested
      - completed

jobs:
  build:
    runs-on: ubuntu-latest
    timeout-minutes: 15
    permissions:
      pull-requests: write
    steps:
      - # https://github.com/orgs/community/discussions/25220#discussioncomment-11316244
        name: 'Get PR context'
        id: pr-context
        env:
          GH_TOKEN: ${{ github.token }}
          PR_TARGET_REPO: ${{ github.repository }}
          PR_BRANCH: |-
            ${{
              (github.event.workflow_run.head_repository.owner.login != github.event.workflow_run.repository.owner.login)
                && format('{0}:{1}', github.event.workflow_run.head_repository.owner.login, github.event.workflow_run.head_branch)
                || github.event.workflow_run.head_branch
            }}
        run: |
          gh pr view --repo "${PR_TARGET_REPO}" "${PR_BRANCH}" \
             --json 'number' --jq '"number=\(.number)"' \
             >> "${GITHUB_OUTPUT}"
      - name: Find Comment
        uses: peter-evans/find-comment@v4
        id: find-comment
        with:
          issue-number: ${{ steps.pr-context.outputs.number }}
          comment-author: 'github-actions[bot]'
          body-includes: "<!-- pr-comment -->"

      # If 'pr' workflow run was 'requested'...
      - if: github.event.action == 'requested' && steps.find-comment.outputs.comment-id != ''
        name: PR workflow started - Update Comment
        uses: peter-evans/create-or-update-comment@v5
        with:
          issue-number: ${{ steps.pr-context.outputs.number }}
          comment-id: ${{ steps.find-comment.outputs.comment-id }}
          edit-mode: replace
          body: |
            <!-- pr-comment -->
            Waiting for [build job](https://github.com/${{github.repository}}/actions/runs/${{github.event.workflow_run.id}}) (at ${{ github.event.workflow_run.head_sha }})...

      # If 'pr' workflow run was 'completed' (but not 'cancelled', that usually means a new job is
      # running, and we don't want to race with it)...
      - if: github.event.action == 'completed' && github.event.workflow_run.conclusion != 'cancelled'
        name: PR workflow completed - Download pr-comment-body.txt
        uses: actions/download-artifact@v4
        continue-on-error: true
        with:
          github-token: ${{ github.token }}
          repository: ${{ github.event.workflow_run.repository.full_name }}
          run-id: ${{ github.event.workflow_run.id }}
          name: pr-comment-body.txt
      - if: github.event.action == 'completed' && github.event.workflow_run.conclusion != 'cancelled'
        name: PR workflow completed - Create pr-comment.txt
        env:
          REPO: ${{github.repository}}
          RUN_ID: ${{github.event.workflow_run.id}}
          RUN_HEAD_SHA: ${{ github.event.workflow_run.head_sha }}
        run: |
          set -eu

          (
            cat << EOF
          <!-- pr-comment -->
          Results for [build job](https://github.com/${REPO}/actions/runs/${RUN_ID}) (at ${RUN_HEAD_SHA}):

          EOF

            if [ -f pr-comment-body.txt ]; then
              cat pr-comment-body.txt
            else
              echo '(No pr-comment-body.txt artifact found from this job.)'
            fi
          ) > pr-comment.txt
      - if: github.event.action == 'completed' && github.event.workflow_run.conclusion != 'cancelled'
        name: PR workflow completed - Post or Update Comment
        uses: peter-evans/create-or-update-comment@v5
        with:
          issue-number: ${{ steps.pr-context.outputs.number }}
          comment-id: ${{ steps.find-comment.outputs.comment-id }}
          edit-mode: replace
          body-path: pr-comment.txt