How can type checking be integrated into the CI/CD process?

Integrating static type checking into CI/CD can be done with static analysis tools such as MyPy, Pyright, or Pytype. These tools are run during the build or testing stage in the CI/CD pipeline.

Integration steps:

1. Installation and configuration: Add the chosen tool to the project dependencies (e.g., requirements.txt or pyproject.toml) and configure it (e.g., mypy.ini).
2. Adding a step in CI/CD: In the CI/CD configuration file (e.g., .github/workflows/main.yml, .gitlab-ci.yml, azure-pipelines.yml), add a separate step (job or step) that runs type checking with the selected tool.
3. Execution and result analysis: CI/CD runs this step on each code change. If errors are found, the step fails, and the pipeline stops, preventing deployment of code with errors.
4. Reports: Some CI/CD platforms and static analysis tools can generate reports on type errors for review in the interface.

Example GitHub Actions step with MyPy:

name: CI

on:
  push:
    branches: [ main ]
  pull_request:
    branches: [ main ]

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v3
    - name: Set up Python 3.9
      uses: actions/setup-python@v4
      with:
        python-version: 3.9
    - name: Install dependencies
      run: |
        python -m pip install --upgrade pip
        pip install -r requirements.txt
        pip install mypy pytest
    - name: Run MyPy
      run: mypy . # Run MyPy on current directory
    - name: Run tests
      run: pytest # Run tests

This ensures that code with incorrect typing does not reach production, increasing reliability and quality.