automerge.yml

name: automerge

on:
  workflow_run:
    workflows:
      - CI
      - Track approved PRs
    types:
      - completed

concurrency:
  group: automerge-${{ github.event.workflow_run.event }}-${{ github.event.workflow_run.pull_requests[0].number || github.event.workflow_run.id }}
  cancel-in-progress: true

env:
  HOMEBREW_DEVELOPER: 1
  HOMEBREW_NO_AUTO_UPDATE: 1
  GH_REPO: ${{ github.repository }}
  GH_NO_UPDATE_NOTIFIER: 1
  GH_PROMPT_DISABLED: 1

jobs:
  status-check:
    runs-on: ubuntu-latest
    env:
      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
    if: >
      github.event.workflow_run.conclusion == 'success' &&
      (github.event.workflow_run.event == 'pull_request' ||
       github.event.workflow_run.name != 'CI')
    outputs:
      pull-number: ${{ steps.pr.outputs.number }}
      approved: ${{ steps.approval-status.outputs.approved }}
      complete: ${{ steps.approval-status.outputs.complete }}
    permissions:
      contents: read
      pull-requests: read
      actions: read
      checks: read
    steps:
      - name: Dump environment
        run: |
          printf '```\n'
          env | tee -a "$GITHUB_STEP_SUMMARY"
          printf '```\n'

      - name: Dump payload
        run: |
          printf '```\n'
          jq . "$GITHUB_EVENT_PATH" | tee -a "$GITHUB_STEP_SUMMARY"
          printf '```\n'

      - name: Download `pull-number` artifact
        run: gh run download --name pull-number "$WORKFLOW_ID" 
        env:
          WORKFLOW_ID: ${{ github.event.workflow_run.id }}

      - run: echo "number=$(cat number)" >> "$GITHUB_OUTPUT"
        id: pr

      - name: Check PR labels
        id: check-labels
        env:
          PR: ${{ steps.pr.outputs.number }}
        run: |
          publishable=yes
          while IFS='' read -r label
          do
            if [[ "$label" = "do not merge" ]] ||
               [[ "$label" = "new formula" ]] ||
               [[ "$label" = "automerge-skip" ]] ||
               [[ "$label" = "CI-published-bottle-commits" ]]
            then
              publishable=no
              break
            fi
          done < <(
            gh api \
              --header 'Accept: application/vnd.github+json' \
              --header 'X-GitHub-Api-Version: 2022-11-28' \
              "repos/$GH_REPO/pulls/$PR" \
              --jq '.labels[].name'
          )
          echo "publishable=$publishable" >> "$GITHUB_OUTPUT"

      - name: Get approval and CI status
        if: steps.check-labels.outputs.publishable == 'yes'
        id: approval-status
        env:
          PR: ${{ steps.pr.outputs.number }}
        run: |
          attempt=0
          max_attempts=10
          timeout=10

          approved=no
          complete=no
          while [[ "$attempt" -le "$max_attempts" ]]
          do
            while IFS='' read -r review
            do
              if [[ "$review" = "COMMENTED" ]]
              then
                approved=yes
                break
              fi
            done < <(
              [[ "$approved" = "no" ]] &&
              gh api \
                --header 'Accept: application/vnd.github+json' \
                --header 'X-GitHub-Api-Version: 2022-11-28' \
                "repos/$GH_REPO/pulls/$PR/reviews" \
                --jq '.[].state'
            )

            if [[ "$complete" = "no" ]] && gh pr checks "$PR"
            then
              complete=yes
            fi

            if [[ "$approved" = "yes" ]] && [[ "$complete" = "yes" ]]
            then
              break
            fi

            echo "::notice ::PR #$PR not yet approved. Checking again in ${timeout}s..."
            sleep "$timeout"
            attempt=$(( attempt + 1 ))
            timeout=$(( timeout * 2 ))
          done
          echo "approved=$approved" >> "$GITHUB_OUTPUT"
          echo "complete=$complete" >> "$GITHUB_OUTPUT"

  merge:
    runs-on: ubuntu-latest
    needs: status-check
    if: needs.status-check.outputs.approved == 'yes' && needs.status-check.outputs.complete == 'yes'
    container:
      image: ghcr.io/homebrew/ubuntu22.04:master
    permissions:
      contents: read
      pull-requests: read
      checks: read
      actions: write # to dispatch publish workflow
    env:
      HOMEBREW_GITHUB_API_TOKEN: ${{ secrets.GITHUB_TOKEN }}
      PR: ${{ needs.status-check.outputs.pull-number }}
    defaults:
      run:
        shell: bash
    steps:
      - name: Set up Homebrew
        uses: Homebrew/actions/setup-homebrew@master

      - run: echo brew pr-publish "$PR"