More cops with parsing Regexp literals

[pocke]

RuboCop will get more power with parsing Regexp literals.
We can introduce https://github.com/ammar/regexp_parser to parse Regexp.

PoC

I already have a PoC project with the regexp_parser gem.
https://github.com/pocke/rubocop-regular_expression
Now it has only one cop, it is RegularExpression/MixedCaptureTypes cop. The cop warns if a Regexp literal has both of named/numbered captures. Because we cannot reference numbered captures if they are mixed.

And I also have other two cop ideas.
pocke/rubocop-regular_expression#1
pocke/rubocop-regular_expression#3

How release it?

I think we have two options to release the cops.

• Merge the cops to RuboCop core
• Release the cops as a RuboCop Plugin

And I like the first option, that merging the cops to RuboCop core.
Because the cops are useful for every RuboCop users. Regexp is used in most projects. So I think RuboCop provides the cops by default.

But the second option has an advantage. We can keep fewer dependencies of RuboCop core by separating the cops as a RuboCop plugin. Because the cops need regexp_parser gem.
But personally I think it is a small advantage.

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So, I propose merging the cops to RuboCop core.
If the core team agrees with the proposal, I will merge the cop to this repository, and transfer the issues of other cop ideas.

[bbatsov]

We can introduce https://github.com/ammar/regexp_parser to parse Regexp.

Looks pretty cool!

And I like the first option, that merging the cops to RuboCop core.
Because the cops are useful for every RuboCop users. Regexp is used in most projects. So I think RuboCop provides the cops by default.

I prefer this option as well.