Suggestion for a new cop: Replace !foo.include?(bar) with foo.exclude?(bar)

[ndbroadbent]

I recently remembered that ActiveSupport adds an exclude? method to Array and String. Before that, I was just using !foo.include?.

I would like to suggest a new cop that detects usage of !foo.include?(bar), and can auto-fix it to: foo.exclude?(bar).

Does that seem like a good idea to anyone else? I really like the exclude? method because it's easier to see the intention. (Similar to unless vs if.)

[ndbroadbent]

I would be happy to submit a PR, but would like to ask for some help because I'm not familiar with the codebase. I think there's already a similar cop that converts if !foo into unless foo. Do you think it would be easy to copy that one and use it as an example? Or are there are some other cops that I should look at for inspiration?

EDIT: Oh I just found a much better example - !blank? vs. present?. I'll copy that one for include? vs. exclude?.

[andyw8]

@ndbroadbent this should help: https://github.com/rubocop-hq/rubocop/blob/master/manual/development.md