There is last I saw. Last I checked Application.app_dir/2 calls :code.lib_dir(:app), which returns the path to the app library directory (which might be a tar file for example, but without the extension), and then it uses Path.join/2 to append it. Where calling :code.lib_dir(:app) instead queries the :code_server directly, which then properly puts the path on to the end of the lib_path, using something similar to Path.join when it is a path, or doing something ‘else’ when it is a packaged file (like a tar file). In addition some custom BEAM builds use a priv directory located and named elsewhere for embedded systems (admittedly this was a decade ago).
