PoC: Optimize predicate methods with attr_reader

[amomchilov]

PoC for #5081

[amomchilov]

It's also possible to make a helper to automate these, but then IDEs won't know about the presence of the generated methods.

module PredicateHelper # This can be mixed into Module, if you're into monkey-patching
  # Given `"foo?"`, this method generates an optimized method that reads from `@foo`.
  def attr_predicate(predicate_name)
    raise ArgumentError unless predicate_name.end_with?("?")
    
    attr_method_name = predicate_name.to_s.delete_suffix("?")
    attr_reader(attr_method_name)
    alias_method(predicate_name, attr_method_name)
    remove_method(attr_method_name)
  end
end

[rmosolgo]

Hey, thanks for proposing this change! I'm definitely interested in it. Another implementation might be write a Rubocop rule which identifies and updates code that uses the "bad" approach. There are a couple other development-related cops here in case you're interested in try that: https://github.com/rmosolgo/graphql-ruby/tree/master/cop/development

[amomchilov]

@rmosolgo Happy to hear! This is definitely rubocop-able. I'd even go so far as to add it upstream to https://github.com/rubocop/rubocop-performance

Would you mind running a quick benchmark on this, to see if it's worthwhile? Btw I wrote up more details in the issue: #5081

I have some env issues, and I won't have time to sort them out until at least next week