Cops defined in gems can conflict even when they are in different namespaces

[haines]

Raising this issue as discussed here: rubocop/rubocop-rspec#834 (comment)

rubocop-rails provides RuboCop::Cop::Rails::HttpStatus, and rubocop-rspec provides RuboCop::Cop::RSpec::Rails::HttpStatus.

Both cops get the same badge, Rails/HttpStatus, and this means that only one cop works (from whichever gem is required last).

Related: rubocop/rubocop-rspec#611

First reported: #5738 (comment)

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Expected behavior

Both cops report offenses.

Actual behavior

Only one cop reports offenses (from whichever gem is required last).

Steps to reproduce the problem

https://gist.github.com/haines/369ac2298ce6fe042865def931e8448b

RuboCop version

0.84.0 (using Parser 2.7.1.3, rubocop-ast 0.0.3, running on ruby 2.7.1 x86_64-darwin19)

[pirj]

Kind of related #5251, but not exactly the same problem.

[dmytro-savochkin]

It looks like a pretty deep problem.

So, this happens due to the fact that RuboCop::Cop::Badge class is built in such a way that it defines a department for a cop by its second to last part of the full class name.
So, RuboCop::Cop::RSpec::Rails::HttpStatus becomes HttpStatus cop with Rails department and RuboCop::Cop::Rails::HttpStatus also becomes HttpStatus cop with the same Rails department.

It seems the code in Badge class can be changed easily enough so that departments are actually more like full_class_name.split('::')[2...-1].join('/') instead of the current full_class_name.split('::')[-2]. After such a change it would be required to ensure that all the dependent gems have updated their settings in .rubocop.yml files. For example, rubocop-rspec gem would need to rename Rails/HttpStatus to RSpec/Rails/HttpStatus. This would need to happen at the same time with rubocop gem itself because rubocop references rubocop-rspec the same way as rubocop-rspec references rubocop.

Another alternative I can think of is to prohibit cops from such deep nesting making sure that there are only 4 levels in their full name.