Redifining module problem because of Code.eval_file in config.exs

Questions / Help
,
1 
defmodule KayaanPrints.EnvLoader do
  def load_env(path \\ ".env") do
    if File.exists?(path) do
      File.stream!(path)
      |> Stream.map(&String.trim/1)
      |> Enum.each(fn line ->
        [key, value] = String.split(line, "=")
        System.put_env(key, value)
      end)
    end
  end
end

So, I’m using the above module to load env variables into System. And in my config file, I have added the below code:

if config_env() in [:dev, :test] do
  Code.eval_file("lib/kayaan_prints/env_loader.ex")
  KayaanPrints.EnvLoader.load_env()
end

It doesn’t throw any error but it shows this as a problem:
redefining module KayaanPrints.EnvLoader (current version defined in memory)

I think it is due to Code.eval_file which loads and evaluates the file everytime it recompiles. Importing module doesn’t work as well. How do i resolve this? if I don’t want to write the whole module code in config.exs file, is there any way i can somehow import it into config?

2

I respect doing things manually but there’s already an established way to do what you want - dotenvy. If you’re not working on a personal project I encourage you to give the library a try.

Edit: If you still what to go with a homegrown solution, check the built-in Config.Provider.

1 Like
3

Thanks a lot sir. But the dotenvy only works during runtime, what if i wanted to load environment variables during compile time without manual code. Are there any libraries available for the same?

4

Something like this may suppress the warning:

if not function_exported?(KayaanPrints.EnvLoader, :__info__, 1) do
  Code.eval_file("lib/kayaan_prints/env_loader.ex")
end

KayaanPrints.EnvLoader.load_env()
1 Like
5

Instead of Code.eval_file/1 one should use compile_path: config in your Mix.Project file. More precisely, elixirc_paths: is your friend.

That said, in mix.exs you are to have

  …
  def project do
    [
      …
      elixirc_paths: elixirc_paths(Mix.env()),
      …
    ]

  defp elixirc_paths(:test), do: ["lib", "extras"]
  defp elixirc_paths(:dev), do: ["lib", "extras"]
  defp elixirc_paths(_), do: ["lib"]

Then move your file from the main tree ("lib" dir) to "extras" on the same level as "lib".
And, finally, use that:

if Code.ensure_loaded?(KayaanPrints.EnvLoader),
  do: KayaanPrints.EnvLoader.load_env()
3 Likes
6

I tried this but it’s still throwing the same warning.

7

This cannot be the case.

Either you forgot to remove KayaanPrints from lib, or you did not recompile the project fresh. Try mix do clean, compile.