UserContext does not clear user when not present

[badosu]

After debugging for quite a while I noticed that Timber does not clear the user set via Timber::Integrations::Rack::UserContext after the user is logged out.

This is due to the fact that the middleware uses Timber::CurrentContext.add that can only change the user context when it is present, but never clears it if the user hash is nil.

As a workaround I am resetting by using a custom user hash:

Timber::Integrations::Rack::UserContext.custom_user_hash = lambda do |env|
    Timber::CurrentContext.remove(:user)
    # My user hash ...
end

Proposed fix is to remove the user from current context before this line or wrap with CurrentContext.with around @app.call as done on SessionContext.

As a sidenote, after enabling debug output I noticed a very high number of calls from this middleware even if just a single request was made.

[askehansen]

Can confirm using clearance.

[badosu]

To clarify, this has considerable impact as many log messages might mislead the operator into thinking they were accessed by a logged-in user while that was not the case (since the user attribute is never cleared).