GitHub Actions for Elixir CI/CD

name: Elixir CI

# Define workflow that runs when changes are pushed to the
# `main` branch or pushed to a PR branch that targets the `main`
# branch. Change the branch name if your project uses a
# different name for the main branch like "master" or "production".
on:
  push:
    branches: [ "main" ]  # adapt branch for project
  pull_request:
    branches: [ "main" ]  # adapt branch for project

# Sets the ENV `MIX_ENV` to `test` for running tests
env:
  MIX_ENV: test

permissions:
  contents: read

jobs:
  test:
    # Set up a Postgres DB service. By default, Phoenix applications
    # use Postgres. This creates a database for running tests.
    # Additional services can be defined here if required.
    services:
      db:
        image: postgres:12
        ports: ['5432:5432']
        env:
          POSTGRES_PASSWORD: postgres
        options: >-
          --health-cmd pg_isready
          --health-interval 10s
          --health-timeout 5s
          --health-retries 5

    runs-on: ubuntu-latest
    name: Test on OTP ${{matrix.otp}} / Elixir ${{matrix.elixir}}
    strategy:
      # Specify the OTP and Elixir versions to use when building
      # and running the workflow steps.
      matrix:
        otp: ['25.0.4']       # Define the OTP version [required]
        elixir: ['1.14.1']    # Define the elixir version [required]
    steps:
    # Step: Setup Elixir + Erlang image as the base.
    - name: Set up Elixir
      uses: erlef/setup-beam@v1
      with:
        otp-version: ${{matrix.otp}}
        elixir-version: ${{matrix.elixir}}

    # Step: Check out the code.
    - name: Checkout code
      uses: actions/checkout@v3

    # Step: Define how to cache deps. Restores existing cache if present.
    - name: Cache deps
      id: cache-deps
      uses: actions/cache@v3
      env:
        cache-name: cache-elixir-deps
      with:
        path: deps
        key: ${{ runner.os }}-mix-${{ env.cache-name }}-${{ hashFiles('**/mix.lock') }}
        restore-keys: |
          ${{ runner.os }}-mix-${{ env.cache-name }}-

    # Step: Define how to cache the `_build` directory. After the first run,
    # this speeds up tests runs a lot. This includes not re-compiling our
    # project's downloaded deps every run.
    - name: Cache compiled build
      id: cache-build
      uses: actions/cache@v3
      env:
        cache-name: cache-compiled-build
      with:
        path: _build
        key: ${{ runner.os }}-mix-${{ env.cache-name }}-${{ hashFiles('**/mix.lock') }}
        restore-keys: |
          ${{ runner.os }}-mix-${{ env.cache-name }}-
          ${{ runner.os }}-mix-

    # Step: Conditionally bust the cache when job is re-run.
    # Sometimes, we may have issues with incremental builds that are fixed by
    # doing a full recompile. In order to not waste dev time on such trivial
    # issues (while also reaping the time savings of incremental builds for
    # *most* day-to-day development), force a full recompile only on builds
    # that are retried.
    - name: Clean to rule out incremental build as a source of flakiness
      if: github.run_attempt != '1'
      run: |
        mix deps.clean --all
        mix clean
      shell: sh

    # Step: Download project dependencies. If unchanged, uses
    # the cached version.
    - name: Install dependencies
      run: mix deps.get

    # Step: Compile the project treating any warnings as errors.
    # Customize this step if a different behavior is desired.
    - name: Compiles without warnings
      run: mix compile --warnings-as-errors

    # Step: Check that the checked in code has already been formatted.
    # This step fails if something was found unformatted.
    # Customize this step as desired.
    - name: Check Formatting
      run: mix format --check-formatted

    # Step: Execute the tests.
    - name: Run tests
      run: mix test

    # Step: Conditionally bust the cache when job is re-run.
    # Sometimes, we may have issues with incremental builds that are fixed by
    # doing a full recompile. In order to not waste dev time on such trivial
    # issues (while also reaping the time savings of incremental builds for
    # *most* day-to-day development), force a full recompile only on builds
    # that are retried.
    - name: Clean to rule out incremental build as a source of flakiness
      if: github.run_attempt != '1'
      run: |
        mix deps.clean --all
        mix clean
      shell: sh