This seems to be an Elixir bug. When the --force flag is given the compile task for the dependency should be reenabled, by default a task is called only once per project/dependency and in this case it seems to have been called earlier at some point.

You have the same bug in your example, you should call Mix.Task.rerun since the task may have already run when mix was started.

Was just about to post back here with my current solution which is probably a very very ugly hack, but it does work:

      case Mix.shell().cmd("mix deps.get") do
        0 ->
          Mix.Task.reenable("compile")
          Mix.Task.run("compile")

          Mix.Project.clear_deps_cache()
          Mix.Project.pop()

          "mix.exs"
          |> File.read!()
          |> Code.eval_string([], file: Path.expand("mix.exs"))

          Mix.Task.run("deps.compile", Enum.map(install_list, &to_string/1))

          Mix.Task.reenable("compile")
          Mix.Task.run("compile")

        exit_code ->
          Mix.shell().info("""
          mix deps.get returned exited with code: `#{exit_code}`
          """)
      end

Not sure I fully understand the question, sorry.

A brief explanation of what I need to do is: I add a dependency to the mix.exs file, and I need to fetch it and look for a mix task defined by it. So I need to add a dep, get it with mix deps.get and then compile it with mix deps.compile. My use case is quite limited, as I know that the app will shut down after running my mix task, so it’s not really a problem if it ends up in a weird state. But this is happening at runtime, not at compile time (since its in a mix task.

Does that answer your question?