How to determine if a class node is X or a descendant of X

[francois]

I found custom cops in RailsEventStore to disallow the use of instance variables and attr_reader in event handlers. I'd like the solution to be more general. Specifically, CopBase asserts that event handler classes are direct descendants of Infra::EventHandler. I'd like to assert that either the ClassNode is a direct descendant of Infra::EventHandler, or any of its ancestors is Infra::EventHandler.

At first, I tried:

module CustomRubocops
  class CopBase < RuboCop::Cop::Base
    private

      def event_handler_class?(node)
        return false unless node.parent_class

        # The "|| event_handler_class?" bit is my addition
        node.parent_class.const_name == 'Infra::EventHandler' || event_handler_class?(node.parent_class)
      end
  end
end

That didn't work because node.parent_class isn't a ClassNode but a data structure.

If this were written without Rubocop, I would have written this as node.ancestors.include?(Infra::EventHandler).

How would I translate that to Rubocop speak?

Thanks and happy new year!

[Earlopain]

Good new year to you as well!

I don't think I 100% understand what you want but since you bring up ancestors from Ruby itself, there is nothing like that for RuboCop. It doesn't have information about things outside of the file it is looking at. So for example, if you define class MyCustomHandler < Infra::EventHandler; end in one file and inherit from it in another, it doesn't know about that hierarchy.

You'd need something much more sophisticated like what sorbet or ruby-lsp do for that to really work. The Rails/HelperInstanceVariable cop is very similar to this I think. It just assumes that everything in app/helpers is actually a helper. Maybe you have a similar folder structure with these event handlers and can make that work?