linting.yml

name: Lint Style

on:
  pull_request:
    types: [opened, synchronize, reopened]
  push:
    branches: [main, master]

concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true

jobs:
  lint:
    runs-on: ubuntu-latest
    
    steps:
      - name: Checkout code
        uses: actions/checkout@v4
        with:
          fetch-depth: 0  # Need full history to detect changed files

      - name: Set up Python
        uses: actions/setup-python@v5
        with:
          python-version: '3.11'

      - name: Get changed Lean files
        id: changed-files
        run: |
          if [ "${{ github.event_name }}" == "pull_request" ]; then
            # For PRs, compare against the base branch
            BASE_SHA="${{ github.event.pull_request.base.sha }}"
            HEAD_SHA="${{ github.sha }}"
          else
            # For pushes, compare against the previous commit
            BASE_SHA="${{ github.event.before }}"
            HEAD_SHA="${{ github.sha }}"
          fi
          
          # Get list of changed .lean files (one per line)
          CHANGED_FILES=$(git diff --name-only --diff-filter=ACMRTUXB "$BASE_SHA" "$HEAD_SHA" | grep '\.lean$' || true)
          
          if [ -z "$CHANGED_FILES" ]; then
            echo "No changed Lean files found"
            echo "has_files=false" >> $GITHUB_OUTPUT
          else
            # Save to file for use in next step
            echo "$CHANGED_FILES" > changed_files.txt
            echo "has_files=true" >> $GITHUB_OUTPUT
          fi

      - name: Run style linter
        run: |
          # Ensure style-exceptions.txt exists (even if empty)
          touch scripts/style-exceptions.txt
          
          if [ "${{ steps.changed-files.outputs.has_files }}" != "true" ]; then
            echo "No changed Lean files to lint"
            exit 0
          fi
          
          # Run linter on changed files only (one file per line)
          # The script will exit with code 1 if there are any errors not in style-exceptions.txt
          # This will cause the CI check to fail
          cat changed_files.txt | xargs -r python3 scripts/lint-style.py