Purerlex

PurerlEx allows you to automatically compile purerl code with mix, both in mix compile and with recompile in iex -S mix.

Assumptions:

All your non-dependency source files are in src/**/*.purs, lib/**/*.purs and/or test/**/*.purs relative to your mix.exs. These are the only places we look for changed files in (via mtime).
Your spago build outputs files in the output folder in the project root.
Your spago project is in the root of the mix project (mix.exs and spago.dhall are in the same folder, not in sub-folders).
You have spago on your path.

First install it by adding purerlex to your list of dependencies in mix.exs:

def deps do
  [
    {:purerlex, "~> 0.11.4"}
  ]
end

Then run mix deps.get in your console to fetch from Hex

Then add the :purerl compiler to (the beginning of) the list of compilers and add "output" to the erlc_paths:

def project do
  [
    ...
    erlc_paths: ["output"], # purerl
    compilers: [:purerl] ++ Mix.compilers(),
    ...
  ]
end

Optionally, for dev builds, you can add the :purserl compiler instead and run a faster compiler fork from https://github.com/drathier/purserl/ .

Docs are also available at https://hexdocs.pm/purerlex.