Performance/RegexpMatch: not enough global variables recognised

[sj26]

Rubocop falsely reports an offense for the RegexpMatch cop on the following code:

if commit_info =~ /^commit \s* ([a-f0-9]+)$/xi
  info[:commit] = $1
end

code.rb:40:8: C: Use match? instead of =~ when MatchData is not used.
if commit_info =~ /^commit \s* ([a-f0-9]+)$/xi
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The match data is being used by $1.

To my eye this looks like the numbered global match variables ($1, $2, ...) need to be added to RegexpMatch#match_gvar?.

---

Expected behavior

No offense reported.

Actual behavior

Offense reported.

Steps to reproduce the problem

Use a Regexp match and global match variables like the example above.

RuboCop version

$ rubocop -V
0.49.1 (using Parser 2.4.0.0, running on ruby 2.4.1 x86_64-darwin16)

[pocke]

Thanks for your report.

I can't reproduce this problem.

test.rb

if commit_info =~ /^commit \s* ([a-f0-9]+)$/xi
  info[:commit] = $1
end

.rubocop.yml

AllCops:
  TargetRubyVersion: 2.4

$ rubocop --only RegexpMatch --cache false
Inspecting 1 file
.

1 file inspected, no offenses detected

To my eye this looks like the numbered global match variables ($1, $2, ...) need to be added to RegexpMatch#match_gvar?.

This gvar is not parsed as gvar, it is parsed as nth-ref.
For example:

$ ruby-parse test.rb
(if
  (send
    (send nil :commit_info) :=~
    (regexp
      (str "^commit \\s* ([a-f0-9]+)$")
      (regopt :i :x)))
  (send
    (send nil :info) :[]=
    (sym :commit)
    (nth-ref 1)) nil)

And rubocop handle nth-ref. https://github.com/bbatsov/rubocop/blob/d87cea2cbaef494df11375900503784b5bc34859/lib/rubocop/cop/performance/regexp_match.rb#L106

Could you give me ruby-parse command output? This command is installed if rubocop is installed.

[sj26]

Apologies, that was a snippet from a larger file. When I reduced the file to only the three lines I supplied it doesn't report an offense. But if I add a little more of the context up to a class method it seems to trigger the problem:

# frozen_string_literal: true
class MyClass
  def self.parse(commit_info)
    if commit_info =~ /^commit \s* ([a-f0-9]+)$/xi
      return $1
    end
  end
end

$ rubocop --only RegexpMatch --cache false app/models/my_class.rb
Inspecting 1 file
C

Offenses:

app/models/my_class.rb:4:8: C: Use match? instead of =~ when MatchData is not used.
    if commit_info =~ /^commit \s* ([a-f0-9]+)$/xi
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

1 file inspected, 1 offense detected

$ ruby-parse app/models/my_class.rb
warning: parser/current is loading parser/ruby24, which recognizes
warning: 2.4.0-compliant syntax, but you are running 2.4.1.
warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.
(class
  (const nil :MyClass) nil
  (defs
    (self) :parse
    (args
      (arg :commit_info))
    (if
      (send
        (lvar :commit_info) :=~
        (regexp
          (str "^commit \\s* ([a-f0-9]+)$")
          (regopt :i :x)))
      (return
        (nth-ref 1)) nil)))

[pocke]

Thanks. I can reproduce it. 👍
I'll work on it.

[sj26]

Thank you! 🙇🏻