heroku-buildpack-dialyxir

Create and cache PLT files during test-compile phase, and run mix dialyzer during test phase.

Usage:

Add

  defp deps do
    [
      {:dialyxir,
       only: [:dev, :test],
       runtime: false,
       github: "jeremyjh/dialyxir",
       ref: "a27b0c55401e5953ba85f4ace94dbdaf002cd0f7"}
    ]

to your mix.exs file and set plt_file to priv/plts/dialyzer.plt

  def project do
    [
      ...
      dialyzer: dialyzer(Mix.env())
    ]
  end

  defp dialyzer(:test) do
    [
      plt_core_path: "priv/plts",
      plt_file: {:no_warn, "priv/plts/dialyzer.plt"}
    ]
  end

  defp dialyzer(_) do
    []
  end

Explenation:

We decided to use commit ref because on dialyxir rc-6 there was still a bug that required a lot of config as a workaround.

We put both core plts and project plt file in the priv/plts for the test environment. The buildpack reads those from the cache during test-compile phase.

The buildpack runs MIX_ENV=test mix dialyzer, so it requires that the project was previously compiled for the :test environment.

We couldn't find a way to clear Heroku's CI cache, so we decided to introduce DIALYXIR_SKIP_CACHE config. When set to true. We won't read current value from the cache effectively recreating PLTs. The PLTs will be normally used in the next run.