How query for Modules that call use on my module

Questions / Help
1

At run time, I need to query for all loaded modules that call use MyUseModule. Say I have:

defmodule MyUseModule do
  defmacro __using__(_) do
    quote do
      # stuff here
    end
  end
end

defmodule Example1 do
  use MyUseModule
end

defmodule Example2 do
  use MyUseModule
end

defmodule Example3 do
  # This module does not use MyUseModule
end

defmodule MyUtil do
   def find_modules_using(MyUseModule) do
      # ???
   end
end

Been working on it for over an hour. Can’t figure it out. Any help would be appreciated.

1 Like
2

Curious what your use case is, but this library could be a good starting point. It generates the AST for each file to analyze for dependencies among modules.

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3

I decided to go another route on this. I’ll just specify the target modules in a config setting.

4

I know it’s a bit late but I think you could use before_compile with a third module (not the one being called with use). Then in the defmacro for it you could set a module attribute that is configured to accumulate with the __CALLER__. I think this is somewhat similar to how protocols are able to get a list of their implementations but it does it with a second pass so as not to risk recompiling the whole app.

I agree though that using config is probably a better approach. Doing it this way could risk some pretty nasty cyclic compile dependencies that you would have a hard time undoing if this were to become a feature that you replied upon

5

I did something similar to what you suggested and kind of had it working. However, then I found a case that broke things. Then I realized that specifying Config entries would be much easier to implement and would make sense for my users as well. Thanks for sharing your perspective.

1 Like