How to add erlang source file to elixir package release to hex

I am using mix to build an Elixir library.

This library includes an erlang module, in the src directory.

When I require my library into a second project using a relative file path (i.e. I have the full source) it works correctly. I have just published this package to hex and when declaring it as a hex dependency in the same second project I get the error that the erlang module is not loaded.

Tokumei 0.8.0 on hex.pm

You're explicitly specifying the list of files to include in the package but the list does not contain src, which is why the files in src are not included. You can either add "src" to that list:

defp package do
  [files: ["lib", "mix.exs", "README*", "LICENSE*", "src"],
   ...
end

or you can remove that key entirely, which will make Hex use the default value of :files which includes many other files, including src.