Check if the Elixir Library Guidelines are followed

[ejpcmac]

Check for each anti-pattern in the Elixir Library Guidelines.

Anti-patterns

Exceptions used for control flow

Currently, the setup!/0, clear!/0 and drop!/0 in the Helpers module only permit to use exceptions. They are used only in the Mix tasks, but could be also used by a user. This should be enhanced in a next version. Maybe these functions should be undocumented or the control flow changed in the Mix tasks.

Application configuration

plug_session_mnesia is currently configured via the application environment. This is discouraged by the guidelines.

Doing any configuration in the plug initialisation is however a bad idea too: the configuration is then frozen at compile time. Plus, plug_session_mnesia is an application, with running processes like the session cleaner.

The main question regarding this kind of configuration is: what should we do if some user wants two webservers with different plug_session_mnesia configurations?

An idea could be to replace the application by a supervisor accepting the configuration as an argument to its init function. But how should we pass this configuration to the session store?