action.yml

name: Setup Elixir Project
description: Checks out the code, configures Elixir, fetches dependencies, and manages build caching.
inputs:
  elixir-version:
    required: true
    type: string
    description: Elixir version to set up
  otp-version:
    required: true
    type: string
    description: OTP version to set up
  #################################################################
  # Everything below this line is optional.
  #
  # It's designed to make compiling a reasonably standard Elixir
  # codebase "just work," though there may be speed gains to be had
  # by tweaking these flags.
  #################################################################
  build-deps:
    required: false
    type: boolean
    default: true
    description: True if we should compile dependencies
  build-app:
    required: false
    type: boolean
    default: true
    description: True if we should compile the application itself
  build-flags:
    required: false
    type: string
    default: '--all-warnings'
    description: Flags to pass to mix compile
  install-rebar:
    required: false
    type: boolean
    default: true
    description: By default, we will install Rebar (mix local.rebar --force).
  install-hex:
    required: false
    type: boolean
    default: true
    description: By default, we will install Hex (mix local.hex --force).
  cache-key:
    required: false
    type: string
    default: 'v1'
    description: If you need to reset the cache for some reason, you can change this key.
outputs:
  otp-version:
    description: "Exact OTP version selected by the BEAM setup step"
    value: ${{ steps.beam.outputs.otp-version }}
  elixir-version:
    description: "Exact Elixir version selected by the BEAM setup step"
    value: ${{ steps.beam.outputs.elixir-version }}
runs:
  using: "composite"
  steps:
    - name: Setup elixir
      uses: erlef/setup-beam@v1
      id: beam
      with:
        elixir-version: ${{ inputs.elixir-version }}
        otp-version: ${{ inputs.otp-version }}

    - name: Get deps cache
      uses: actions/cache@v2
      with:
        path: deps/
        key: deps-${{ inputs.cache-key }}-${{ runner.os }}-${{ hashFiles('**/mix.lock') }}
        restore-keys: |
          deps-${{ inputs.cache-key }}-${{ runner.os }}-

    - name: Get build cache
      uses: actions/cache@v2
      id: build-cache
      with:
        path: _build/${{env.MIX_ENV}}/
        key: build-${{ inputs.cache-key }}-${{ runner.os }}-${{ inputs.otp-version }}-${{ inputs.elixir-version }}-${{ env.MIX_ENV }}-${{ hashFiles('**/mix.lock') }}
        restore-keys: |
          build-${{ inputs.cache-key }}-${{ runner.os }}-${{ inputs.otp-version }}-${{ inputs.elixir-version }}-${{ env.MIX_ENV }}-

    - name: Get Hex cache
      uses: actions/cache@v2
      id: hex-cache
      with:
        path: ~/.hex
        key: build-${{ runner.os }}-${{ inputs.otp-version }}-${{ inputs.elixir-version }}-${{ hashFiles('**/mix.lock') }}
        restore-keys: |
          build-${{ runner.os }}-${{ inputs.otp-version }}-${{ inputs.elixir-version }}-

    # In my experience, I have issues with incremental builds maybe 1 in 100
    # times 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),
    # I force a full recompile only on builds that we retry.
    - 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

    - name: Install Rebar
      run: mix local.rebar --force
      shell: sh
      if: inputs.install-rebar == 'true'

    - name: Install Hex
      run: mix local.hex --force
      shell: sh
      if: inputs.install-hex == 'true'

    - name: Install Dependencies
      run: mix deps.get
      shell: sh

    # Normally we'd use `mix deps.compile` here, however that incurs a large
    # performance penalty when the dependencies are already fully compiled:
    # https://elixirforum.com/t/github-action-cache-elixir-always-recompiles-dependencies-elixir-1-13-3/45994/12
    #
    # Accoring to Jose Valim at the above link `mix loadpaths` will check and
    # compile missing dependencies
    - name: Compile Dependencies
      run: mix loadpaths
      shell: sh
      if: inputs.build-deps == 'true'

    - name: Compile Application
      run: mix compile ${{ inputs.build-flags }}
      shell: sh
      if: inputs.build-app == 'true'