Fix the load order issues of Sweeping module

[tiegz]

WHAT

Remove Concern from the Sweeping module so we can directly extend it in ActionController::Base

WHY

Basically this is what happens, in the context of ActionController when the app is booting:

1. Base loads and includes the Caching module
2. rails-observers railtie is then triggered to include Caching::Sweeping concern as a dependency of Caching, but it doesn't actually get included because Caching is a concern too.
3. However Caching was already included in step 1, so Caching::Sweeping never gets included in Base and people run into this error: Undefined method `cache_sweeper' or uninitialized constant ActionController::Caching::Sweeper #4

Note: the tests for this were working before because it didn't use the railtie to load Sweeping. It just directly loaded the files with Sweeping in them before it loaded ActionController::Base.

FIXES

#4

[tiegz]

(this is the simplest solution I had. Other possibilities include moving Sweeping out of the Caching module)

[tiegz]

just found the same issue in thsi gem: https://github.com/rails/actionpack-page_caching

And I assume it exists here too: https://github.com/rails/actionpack-action_caching

So I guess whatever solution we use here can be applied in those.

[khustochka]

Hi @tiegz

Thanks for your work.

Just for the record I never had problems with actionpack-page_caching similar to those I had with rails-observers.