Rubocop expects formatters to be a string

[macumber]

I found that this change is needed using ruby 3.2.2 as rubocop expects BUILTIN_FORMATTERS_FOR_KEYS to be a map of keys to strings and not to classes, see rubocop-1.63.5\lib\rubocop\formatter\formatter_set.rb

Without this change I get the error "no implicit conversion of Class into String" when trying to run rubocop -d -f extension_review -o report.html

---

Before submitting the PR make sure the following are checked:

• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Run bundle exec rake. It executes all tests and RuboCop for itself, and generates the documentation.

[thomthom]

It will then look for 'ExtensionReviewFormatter' in the RuboCop::Formatter namespace?

[macumber]

Yes, RuboCop::Formatter.const_get(formatter_name) at https://github.com/rubocop/rubocop/blob/master/lib/rubocop/formatter/formatter_set.rb#L102 is calling const_get on the RuboCop::Formatter module. The argument to const_get is a symbol or a string, https://www.rubydoc.info/stdlib/core/Module:const_get. Maybe this used to accept a Class in Ruby 2.x but it seems to not accept that in Ruby 3.x.

[thomthom]

Ok. Thank you for the PR. I guess the CI tests never tests the custom formatter.

I had a quick look at RuboCop docs, and it appear to still be lacking a clear good API to add custom extensions and formatters without monkey patching some parts of RuboCop. So this has always been something that has a higher risk of breaking.