lint_pr.yml

name: Linting on PR, with stricter rules on new code

on: [pull_request]

jobs:
  lint:

    runs-on: ubuntu-latest

    strategy:
      fail-fast: false
      matrix:
        python-version: [3.7, 3.8, 3.9, '3.10', '3.11']

    steps:
    - name: Checkout PR merge commit
      uses: actions/checkout@v3

    - name: Set up Python ${{ matrix.python-version }}
      uses: actions/setup-python@v4
      with:
        python-version: ${{ matrix.python-version }}

    - name: Install dependencies
      run: |
        python -m pip install --upgrade pip
        python -m pip install flake8 flake8-docstrings

    - name: Fetch pull request target branch
      run: git fetch origin ${{ github.base_ref }}

    - name: Lint with standard ignores on modified files
      shell: bash
      run: |
        flake8 . --count --show-source --statistics | sed -r 'h;s/^(\S+):([0-9]+):([0-9]+): /::error file=\1,line=\2,col=\3::/p;g'

    - name: Lint changes with flake8
      shell: bash
      # Reduced list of ignores, applied on the changed lines only
      run: |
        git diff -z --name-only FETCH_HEAD -- '**.py' | xargs -r0 flake8 --exit-zero --ignore=D107,D200,D210,D413,E251,E302,E303,W504 > errors
        git diff FETCH_HEAD -U0 -- '**.py' | sed -rn -e '/^\+\+\+ /{s,^\+\+\+ ./,,;h}' -e '/^@@ /{G;s/^@@ -[0-9,]+ \+([0-9,]+) @@.*\n(.*)/\2,\1/p}' | (
           while IFS=, read file start lines; do for (( l = start ; l < $start + ${lines:-1}; ++l )); do echo "^$file:$l:"; done; done
        ) > changed_lines
        # Invert return value, i.e. error iff matches
        ! grep -f changed_lines errors | sed -r 'h;s/^(\S+):([0-9]+):([0-9]+): /::error file=\1,line=\2,col=\3::/p;g'