I have a complex app configuration that I’ve made much simpler via a custom module. I don’t want to implement it as a config provider because I have to use it during development as well. But trying to access it from config.exs leads to a bit of a chicken-and-egg situation because config.exs is loaded before the app is compiled.

I’ve tricked Elixir into making this work in both mix mode and release mode, but it’s really hacky and I kind of hate it. I’d love to know if there’s a better way to accomplish what I’m doing. Here’s how it goes:

lib/my_configurator.ex

Define the module if it’s not already defined.

if !function_exported?(:MyConfigurator, :__info__, 1) do
  defmodule MyConfigurator do
    def prefix, do: System.get_env("CONFIG_PREFIX", "")
    def prefix(str), do: prefix() <> "-" <> str
    ...
  end
end

mix.exs

At the top of mix.exs I added

Code.require_file("lib/my_configurator.ex")

Yeah. Like I said. Ugly. Anyway, All of that makes MyConfigurator available from within config.exs and all of the files it loads via import_config when run via mix. And it’s available from releases.exs in the release by virtue of having been compiled from lib. But you can see why I’d appreciate a more elegant solution.

Is there one?