Reporting Flake8 finding as GitHub Annotations

In Extending GitHub Actions with Annotations the output of GitHub Actions was transformed into Annotations that could be shown in the web interface. The example shows that part for Flake8 which is a framework for different plugins to be combined and scan Python code on common mistakes and improvements. But later in 2023 a plugin was release for Flake8 to generate a report that can be used by GitHub Annotations.

Original example with a separate JSON to match

- name: Add problem matcher
  run: echo "::add-matcher::.github/flake8-problem-matcher.json"

- name: Lint with flake8
  run: |
    # stop the build if there are Python syntax errors or undefined names
    flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
    # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
    flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics

By changing to GitHub Actions workflow file as shown in the example below, then the plugin flake8-github-annotations is installed and the flake8 commands are executed with the option --format github like as with yamllint. The lines to add the probem matcher can also be removed.

Example of a basic CI workflow

---
name: CI

on:
  push:
    branches:
      - master
  pull_request:
    branches:
      - master

jobs:
  lint:
    name: Linting the Code Base
    runs-on: ubuntu-latest

    steps:
      - name: Checkout Code
        uses: actions/checkout@v3

      - name: Install dependencies
        run: |
          python -m pip install --upgrade pip
          python -m pip install flake8 yamllint flake8-github-annotations

      - name: Lint with yamllint
        run: |
          yamllint . --format github

      - name: Lint with flake8
        run: |
          # stop the build if there are Python syntax errors or undefined names
          flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics --format github
          # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
          flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics --format github

With flake8-github-annotations in place the CI workflow becomes simpler to read and maintain as no custom changes are needed anymore. The only drawback for now is that all findings are reported as an error instead of errors and warnings for example.

Check Python with Flake8 Bugbear   Using environment variables in a devcontainer