Add forward slash to LITERAL_REGEX

[eugeneius]

The forward slash character has no special meaning when it appears in a regex. This will let Performance/StartWith and Performance/EndWith correct code like the following:

path =~ %r{/\z}

To:

path.end_with?('/')

I noticed this problem thanks to @eregon's comment here: rails/rails#37504 (comment)

LITERAL_REGEX is only used in RuboCop Performance, so I couldn't add a test to demonstrate the new behaviour. Arguably the constant should be defined there instead, but removing it from RuboCop would introduce an incompatibility with all existing versions of RuboCop Performance. I opted to update the constant in-place; let me know if another approach is preferable.

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[bbatsov]

LITERAL_REGEX is only used in RuboCop Performance, so I couldn't add a test to demonstrate the new behaviour. Arguably the constant should be defined there instead, but removing it from RuboCop would introduce an incompatibility with all existing versions of RuboCop Performance. I opted to update the constant in-place; let me know if another approach is preferable.

@koic I guess we should just move this constant to the rubocop-performance project then.

[koic]

@bbatsov Yeah. That seems good to me.

@eugeneius Could you make the constant LITERAL_REGEX to RuboCop Performance and add tests?
As you are concerned, combining RuboCop 0.75.1 or lower with RuboCop Performance 1.15.0 or lower will result in an incompatibility error.

I opted to update the constant in-place; let me know if another approach is preferable.

So, I'd like to leave this constant in RuboCop core for a while. Perhaps the constant will be removed after future release of RuboCop 0.76 and higher.
(Perhaps TracePoint, etc is used, it seems technically possible to display a warning about breaking change, but it is not a good way to do it 😅 )

[bbatsov]

Agreed. I guess we should fix this in RuboCop for now and move the constant to rubocop-performance down the road.