check-n-lines-changed.yaml

---
env:
  GITHUB_TOKEN: '${{ secrets.GITHUB_TOKEN }}'
  MAX_LINES_ADDED: 300
  MAX_LINES_REMOVED: 500
  OVERRIDE_N_APPROVALS: 2
jobs:
  check-n-lines-changed:
    env:
      # If run from a merge group, the action should not run. However there is
      # no way to exit early in GitHub actions per
      # https://github.com/actions/runner/issues/662, so using a conditional
      # check for each step serves as a workaround.
      IS_MERGE_GROUP: '${{ github.event_name == ''merge_group'' }}'
    runs-on: 'ubuntu-latest'
    steps:
    - uses: 'actions/checkout@v4'
      with:
        fetch-depth: 0
    - id: 'get-pr-number'
      if: '${{ env.IS_MERGE_GROUP != ''true'' }}'
      name: 'Get PR number'
      # yamllint disable rule:indentation
      run: |
        PR_NUMBER=$(
          if [ "${{ github.event_name }}" = "pull_request_review" ]; then
            echo "${{ github.event.pull_request.number }}"
          else
            echo "${{ github.event.pull_request.number }}"
          fi
        )
        if [ -z "$PR_NUMBER" ]; then
          echo "No PR number found. Exiting."
          exit 1
        fi
        echo "number=$PR_NUMBER" >> $GITHUB_OUTPUT
    # yamllint enable rule:indentation
    - id: 'get-base-branch'
      if: '${{ env.IS_MERGE_GROUP != ''true'' }}'
      name: 'Get PR base branch'
      run: |
        PR_NUMBER="${{ steps.get-pr-number.outputs.number }}"
        BASE=$(gh pr view "$PR_NUMBER" --json baseRefName -q '.baseRefName')
        echo "Base branch: $BASE"
        echo "base_branch=$BASE" >> $GITHUB_OUTPUT
    - id: 'get-insertions'
      if: '${{ env.IS_MERGE_GROUP != ''true'' }}'
      name: 'Get number of lines added'
      # yamllint disable rule:indentation
      run: |
        BASE_BRANCH="${{ steps.get-base-branch.outputs.base_branch }}"
        git fetch origin $BASE_BRANCH
        INSERTIONS=$(
          git diff --stat origin/$BASE_BRANCH | \
          tail -n1 | grep -oP '\d+(?= insertion)' || echo "0"
        )
        echo "Number of lines added: $INSERTIONS"
        echo "insertions=$INSERTIONS" >> $GITHUB_OUTPUT
    # yamllint enable rule:indentation
    - id: 'get-deletions'
      if: '${{ env.IS_MERGE_GROUP != ''true'' }}'
      name: 'Get number of lines removed'
      # yamllint disable rule:indentation
      run: |
        BASE_BRANCH="${{ steps.get-base-branch.outputs.base_branch }}"
        git fetch origin $BASE_BRANCH
        DELETIONS=$(
          git diff --stat origin/$BASE_BRANCH | \
          tail -n1 | grep -oP '\d+(?= deletion)' || echo "0"
        )
        echo "Number of lines removed: $DELETIONS"
        echo "deletions=$DELETIONS" >> $GITHUB_OUTPUT
    # yamllint enable rule:indentation
    - id: 'get-approvals'
      if: '${{ env.IS_MERGE_GROUP != ''true'' }}'
      name: 'Get number of active approving reviews'
      # Sum up the number of approvals across all reviewers, only counting a
      # review as approving if it is the last review by that reviewer.
      # yamllint disable rule:indentation
      run: |
        APPROVALS=$(
          gh pr view ${{ steps.get-pr-number.outputs.number }} \
            --json reviews | \
            jq '
              .reviews
              | group_by(.user.login)
              | map(last)
              | map(select(.state == "APPROVED"))
              | length
            '
        )
        echo "Number of approvals: $APPROVALS"
        echo "approvals=$APPROVALS" >> $GITHUB_OUTPUT
    # yamllint enable rule:indentation
    - if: '${{ env.IS_MERGE_GROUP != ''true'' }}'
      name: 'Check size versus approvals'
      # yamllint disable rule:indentation
      run: |
        INSERTIONS="${{ steps.get-insertions.outputs.insertions }}"
        DELETIONS="${{ steps.get-deletions.outputs.deletions }}"
        echo "$INSERTIONS lines added (max ${{ env.MAX_LINES_ADDED }})"
        echo "$DELETIONS lines removed (max ${{ env.MAX_LINES_REMOVED }})"
        NEEDS_OVERRIDE="false"
        if [ "$INSERTIONS" -gt "${{ env.MAX_LINES_ADDED }}" ]; then
          NEEDS_OVERRIDE="true"
        fi
        if [ "$DELETIONS" -gt "${{ env.MAX_LINES_REMOVED }}" ]; then
          NEEDS_OVERRIDE="true"
        fi
        if [ "$NEEDS_OVERRIDE" = "true" ]; then
          APPROVALS="${{ steps.get-approvals.outputs.approvals }}"
          OVERRIDE_N_APPROVALS="${{ env.OVERRIDE_N_APPROVALS }}"
          if [ "$APPROVALS" -ge "$OVERRIDE_N_APPROVALS" ]; then
            echo "✅ Changes exceeded limits but have required approvals"
          else
            echo "❌ Too many changes. Need $OVERRIDE_N_APPROVALS approvals"
            if [ "${{ github.event_name }}" = "pull_request" ]; then
              echo "If the PR author hasn't updated this PR since enough"
              echo "approvals were left, you must manually trigger a re-run"
            fi
            exit 1
          fi
        else
          echo "✅ Changes within limits"
        fi
# yamllint enable rule:indentation
name: 'Check number of lines changed'
'on':
  merge_group: null
  pull_request:
    branches-ignore:
    - 'production'
    - 'fallback'
  pull_request_review: null
...