[Fix #8621] Helpful Infinite Loop message

[iSarCasm]

Closes #8621

Adds the information about which Cops exactly caused an infinite loop

Tracks the corrected offenses on each iteration.

In the case of exceeding MAX_ITERATIONS, it just returns cop names from the latest iteration.
In the case of duplicated sources, it returns a list of iterations (with cop names) starting from the first time this exact source has already been generated. In most cases, I imagine there would only be 2 or 3 iterations between looped states but it should handle all cases.

Examples:

• Test/ClassMustBeAModuleCop -> Test/ModuleMustBeAClassCop
• Test/ClassMustBeAModuleCop, Test/AtoB -> Test/ModuleMustBeAClassCop, Test/BtoA
• Test/AtoB -> Test/BtoC -> Test/CtoA

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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.
• Added an entry to the Changelog if the new code introduces user-observable changes. See changelog entry format.
• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Run bundle exec rake default. It executes all tests and RuboCop for itself, and generates the documentation.

[bbatsov]

The proposed changes look good to me overall. Let's also hear what @marcandre and @koic think about them, though.

[marcandre]

Fabulous! ♥️

Only nitpick is that I would convert an array to string with .join(', ') instead of .to_s. In the typical cases, Some/Cop -> Some/OtherCop is nicer than [Some/Cop] -> [Some/OtherCop].

[iSarCasm]

Fabulous! ♥️

Only nitpick is that I would convert an array to string with .join(', ') instead of .to_s. In the typical cases, Some/Cop -> Some/OtherCop is nicer than [Some/Cop] -> [Some/OtherCop].

@marcandre So in case of more than 1 conflicting cop it should be Test/ClassMustBeAModuleCop, Test/AtoB ->Test/ModuleMustBeAClassCop, Test/AtoB instead of ["Test/ClassMustBeAModuleCop", "Test/AtoB"] -> ["Test/ModuleMustBeAClassCop", "Test/BtoA"], right?

P.S: Updated it already

[marcandre]

P.S: Updated it already

Cool, LGTM 👍

[koic]

This looks good to me. I think this information can be a good hint to solve the infinite loop error 👍

[bbatsov]

Thanks!