Caching Dialyzer output with GitHub Actions

Hey everyone!

I’m curious why Dialyzer does a full analysis even when I cache the _build directory when using GitHub Actions. My deps directory is also cached and that works fine. It doesn’t try to pull deps if they’re cached.

My Dialyzer setup is pretty vanilla. I include dialyxir (1.0.0-rc) in my project and run mix dialyzer. No additional configuration in mix.exs.

Here’s the relevant section for my workflow config.

Thanks in advance to anyone that can help.

dialyzer:
  runs-on: ubuntu-latest

  strategy:
    matrix:
      elixir: [1.9-alpine]

    steps:
      - uses: actions/checkout@v1

      - uses: actions/cache@v1

        with:
          path: deps

          key: dependencies-${{ hashFiles('mix.lock') }}

      - uses: actions/cache@v1

        with:
          path: _build

          key: build-${{ hashFiles('mix.lock') }}

      - name: Pull elixir:${{ matrix.elixir }}

        run: docker pull elixir:${{ matrix.elixir }}

      - name: Run mix dialyzer

        run: |
          cmd='
            mix local.hex --force;
            mix local.rebar --force;
            mix deps.get;
            mix dialyzer;
          '

          docker run \
            --mount type=bind,src=`pwd`,target=/usr/src/malomo-bus \
            -w /usr/src/malomo-bus elixir:${{ matrix.elixir }} \
            /bin/ash -c "$cmd"