check-format.yml

name: Format check

on:
  push:

  pull_request:

  workflow_dispatch:

jobs:
  clang-format:
    name: Check format using clang-format-diff
    runs-on: ubuntu-24.04

    steps:
      # Checkout the repository with full history to enable git diff
      - name: Checkout repository
        uses: actions/checkout@v6
        with:
          fetch-depth: 0

      - name: Install pinned clang-format
        run: |
          export DEBIAN_FRONTEND=noninteractive
          export TZ=Etc/UTC
          sudo apt-get update
          sudo apt-get install -y clang-format-20

      - name: Show clang-format version
        run: clang-format --version

      # Run clang-format on changed source files only
      - name: Run clang-format diff on changed files
        env:
          BASE_REF: ${{ github.event.pull_request.base.ref }}
        run: |
          echo "Fetching base branch $BASE_REF..."
          git fetch origin $BASE_REF

          echo "Running clang-format diff..."
          git diff -U3 origin/$BASE_REF...HEAD -- '*.c' '*.cpp' '*.h' '*.hpp' \
            | clang-format-diff-20 -p1 -style=file > clang-format.diff

          # If diff is non-empty, create GitHub annotations
          if [ -s clang-format.diff ]; then
            echo "Found formatting issues"
            cat clang-format.diff
            echo "Generating GitHub annotations for formating issues ..."
            while IFS= read -r line; do
              if [[ $line =~ ^\+\+\+ ]]; then
                file=${line#+++ b/}
              elif [[ $line =~ ^@@ ]]; then
                lineno=$(echo "$line" | sed -E 's/^@@ -[0-9]+,[0-9]+ \+([0-9]+),[0-9]+ @@.*/\1/')
              elif [[ -n $line && $line =~ ^\+ ]]; then
                echo "::error file=$file,line=$lineno::Bad formatting: ${line#?}"
                lineno=$((lineno+1))
              elif [[ -n $line && ! $line =~ ^- ]]; then
                lineno=$((lineno+1))
              fi
            done < clang-format.diff
            exit 1
          else
            echo "No formatting issues detected."
          fi