Autocorrect for Style/CaseLikeIf changes behaviour of regex match data

[krauselukas]

The rubocop auto-correct for the Style/CaseLikeIf cop had some unexpected behaviour when dealing with the ruby match operator in combination with if/elsif statements.
To be more precise, the match data object is not returned anymore after moving the regex condition to a case statement.

---

Expected behavior

The Style/CaseLikeIf cop takes the =~ match operator into account.

Actual behavior

The Style/CaseLikeIf cop autocorrect changed the behaviour of the code, which lead to faulty results and failing test's.

Steps to reproduce the problem

Before

params[:command] = 'set-disable'
if params[:command] == 'remove'
  # do something
elsif %r{^set-(?<status>disable|enable)$} =~ params[:command]
  puts status
end

Result
disable

After auto-correct

params[:command] = 'set-disable'
case params[:command]
when 'remove'
  # do something
when /^set-(?<status>disable|enable)$/
  puts status
end

Result
NameError (undefined local variable or method 'status' for main:Object)

See also openSUSE/open-build-service@6909ea7

RuboCop version

frontend@3099cfde322d:/obs/src/api> rubocop -V
0.88.0 (using Parser 2.7.1.4, rubocop-ast 0.1.0, running on ruby 2.5.8 x86_64-linux-gnu)

[dmytro-savochkin]

I think I can come up with something. Actually I wrote the code to fix this actual problem but also want to fix some other edge-cases. Will probably make a PR in a couple of weeks.

[marcandre]

Indeed, this is because the only way to get local variables set this way is /literal_regex(?<named>)/ =~ var. If the regexp is stored in a variable or constant and used later with =~ that won't work, or if used with === like here it won't work either. 🤷‍♂️