Get app versions at compile time?

You cannot access the application spec because your application is being compiled. Fortunately, you can access information about your Mix project like this:

defmodule Foo do
  IO.inspect(Mix.Project.config()[:version])
end

Thank you! Is it possible to also get versions of dependencies?

You can grab information about your deps in that project config too.

I believe the dep apps are automatically loaded (if not, you can Application.load/1 them) so you can definitely call Application.spec/1 and it will work

thank you, that was the trick!

Oiy, is almost working – this does not work for mix compile
maybe I have to do something in application start?

your MixProject module is nothing special, it’s a module like any other (I mean aside from the fact that it’s only available at compile time). Make the deps/0 function public instead of private, and you’re good to go.

it just occurred to me that won’t tell you what the version is, just what version you wanted. You could also read the mix.lock file using Code.eval_file/1

Ah, of course I did not think of this!

"mix.lock"
  |> Code.eval_file()
  |> Tuple.to_list()
  |> Enum.at(0)
  |> Enum.reduce(%{}, fn
    {app, {:hex, _, version, _, _, _, _, _}}, acc ->
      Map.put(acc, app, version)

    {app, {:git, _, _, [{_, version}]}}, acc ->
      Map.put(acc, app, version)
  end)

However this has lots of warnings: warning: found quoted keyword "jason" but the quotes are not required.

Is there a way to avoidthose?

Is this on purpose that the mix.lock contains bad format? Shouldn’t have no quotes for keys or use =>?

I found solution to this: just add mix.lock to .formatter.exs:

[
  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}", "mix.lock"]
]

and then the above works!

you may want to use elem/2 instead of Tuple.to_list |> Tuple.at