simple example for caching with a composite action

composite_cache_example.yml

# .github/actions/setup/action.yaml

name: "mix cache"
description: "Setup an elixir mix project and restore cache"

inputs:    
   cache-version: 
     description: "Optional cache version. Any string is valid. Default to '0'"
     required: false
     default: 0
outputs:
  cache-hit:
    description: "Forward actions/cache cache-hit output"
    value: ${{ steps.mix-cache.outputs.cache-hit }}

runs:
  using: "composite" # Mandatory parameter
  steps:
     - name: get tool versions
       run: ./.github/scripts/gh_get_tool_versions.sh
       id: versions
     - name: setup
       uses: erlef/setup-beam@v1
       with:
         otp-version: ${{ steps.versions.outputs.otp-version }}
         elixir-version: ${{ steps.versions.outputs.elixir-version }}
    - name: restore-deps
      uses: actions/cache@v1
      with:
        path: deps
        key: ${{ runner.os }}-mix-${{ inputs.otp-version }}-${{ inputs.elixir-version }}-${{ inputs.cache-version }}-${{ hashFiles(format('{0}{1}', github.workspace, '/mix.lock')) }}
    - name: restore-build
      uses: actions/cache@v1
        with:
          path: _build
          key: ${{ runner.os }}-build-${{ inputs.otp-version }}-${{ inputs.elixir-version }}-${{ inputs.cache-version }}-${{ hashFiles(format('{0}{1}', github.workspace, '/mix.lock')) }}
        

# .github/actions/setup/action.yaml

name: "dialyzer-cache"
description: "Setup an elixir mix project and restore cache"

inputs:    
   cache-version: 
     description: "Optional cache version. Any string is valid. Default to '0'"
     required: false
     default: 0
outputs:
  cache-hit:
    description: "Forward actions/cache cache-hit output"
    value: ${{ steps.mix-cache.outputs.cache-hit }}

runs:
  using: "composite" # Mandatory parameter
  steps:
     - name: setup
       uses: ./.github/actions/setup
         with: inputs.cache-version 



---
name: ci
on:
  push:
    branches:
      - main
  pull_request:
    types: [opened, synchronize]

env:
  MIX_ENV: test
  cache-version: '0'

jobs:
  build:
    name: Build
    runs-on: ubuntu-latest
    steps:
      - name: checkout
        uses: actions/checkout@v2
      - name: setup
      - uses: ./.github/actions/setup
        with:
          cache-version: env.cache-version 
      - name: deps.get
        run: mix deps.get
      - name: compile
        run: mix compile --warnings-as-errors

  format:
    name: Format
    needs: build
    runs-on: ubuntu-latest
    steps:
      - name: checkout
        uses: actions/checkout@v2
      - name: setup
      - uses: ./.github/actions/setup
        with:
          cache-version: env.cache-version 
      - name: format
        run: mix format --check-formatted

  credo:
    name: Credo
    needs: build
    runs-on: ubuntu-latest
    steps:
      - name: checkout
        uses: actions/checkout@v2
      - name: setup
      - uses: ./.github/actions/setup
        with:
          cache-version: env.cache-version    
      - name: credo
        run: mix credo --config-name=currently_passing

  dialyzer:
    needs: build
    name: Dialyzer
    runs-on: ubuntu-latest
    env:
      MIX_ENV: dev
    steps:
      - name: checkout
        uses: actions/checkout@v2
      - name: setup
        uses: ./.github/actions/setup
        with:
          cache-version: env.cache-version    
      - name: restore-dev-build
        uses: actions/cache@v1
        with:
          path: _build
          key: ${{ runner.os }}-build-${{ steps.versions.outputs.otp-version }}-${{ steps.versions.outputs.elixir-version }}-${{ env.cache-version }}-${{ hashFiles(format('{0}{1}', github.workspace, '/mix.lock')) }}
      - name: restore-plts
        uses: actions/cache@v1
        with:
          path: ~/.plts
          key: ${{ runner.os }}-dialyzer-${{ steps.versions.outputs.otp-version }}-${{ steps.versions.outputs.elixir-version }}-${{ env.cache-version }}-${{ hashFiles(format('{0}{1}', github.workspace, '/mix.lock')) }}
      - name: dialyze
        run: mix dialyzer

  test:
    needs: build
    name: Test
    runs-on: ubuntu-latest
    steps:
      - name: checkout
        uses: actions/checkout@v2
      - name: setup-project
        uses: ./.github/actions/setup-project
        with:
          cache-version: env.cache-version    
      - name: test
        run: mix coveralls