Incorrect Regexp fix for Style/RedundantRegexpArgument with extraneous escaped double-quote

[drsharp]

We discovered a strange corner-case where a gsub that includes an unnecessarily-escaped double-quote gets autocorrected in a way that affects the gsub. I believe this is an anomaly because Ruby handles /"/ and /\"/ the same way... that is: the extra back-slash is extraneous but the Rubocop rule doesn't handle it as such.

Ruby apparently treats these the same:

irb(main):006:0> "one \" two".gsub(/"/, 'X')
=> "one X two"
irb(main):007:0> "one \" two".gsub(/\"/, 'X')
=> "one X two"

---

Expected behavior

When passed through Style/RedundantRegexpArgument and autocorrected the following line:

"an escaped \"double-quote\" value".gsub(/\"/, """)

should turn into:

"an escaped \"double-quote\" value".gsub('"', """)

both lines run as normal Ruby output the gsub the same way:

♯ irb
irb(main):001:0> "an escaped \"double-quote\" value".gsub(/\"/, """)
=> "an escaped "double-quote" value"
irb(main):002:0> "an escaped \"double-quote\" value".gsub('"', """)
=> "an escaped "double-quote" value"

Actual behavior

"an escaped \"double-quote\" value".gsub(/\"/, """)

becomes instead:

"an escaped \"double-quote\" value".gsub('\"', """)

(the \ is left in there). And that doesn't process the input string the same way:

irb(main):003:0> "an escaped \"double-quote\" value".gsub('\"', """)
=> "an escaped \"double-quote\" value"

Steps to reproduce the problem

I just created a simple test.rb file with this in it:

#!/usr/bin/env ruby
test_value = 'something with "quotes" around it'
gsub_value = test_value.gsub(/\"/, """)

puts "Test Value: #{test_value.inspect}"
puts "Gsub Value: #{gsub_value.inspect}"

I verified it ran fine and the output was as expected:

♯ ruby test.rb
Test Value: "something with \"quotes\" around it"
Gsub Value: "something with "quotes" around it"

I then ran the rubocop with autocorrect:

♯ rubocop test.rb --autocorrect
Inspecting 1 file
C

Offenses:

test.rb:3:30: C: [Corrected] Style/RedundantRegexpArgument: Use string '\"' as argument instead of regexp /\"/.
gsub_value = test_value.gsub(/\"/, """)
                             ^^^^

which changed it to:

#!/usr/bin/env ruby
test_value = 'something with "quotes" around it'
gsub_value = test_value.gsub('\"', """)

puts "Test Value: #{test_value.inspect}"
puts "Gsub Value: #{gsub_value.inspect}"

But now that runs as:

♯ ruby test.rb                 
Test Value: "something with \"quotes\" around it"
Gsub Value: "something with \"quotes\" around it"

which means the gsub isn't working.

RuboCop version

I originally tested this on 1.64.1 as that is what we are using in our Ruby 2.7.6 main environment:

♯ rubocop -V
1.64.1 (using Parser 3.3.4.2, rubocop-ast 1.32.3, running on ruby 2.7.6) [arm64-darwin23]
  - rubocop-minitest 0.34.5
  - rubocop-performance 1.21.1
  - rubocop-rails 2.23.1

But I also tested it on the latest version in our Ruby 3.3.3 environment and can confirm it fails there as well:

♯ rubocop -V
1.68.0 (using Parser 3.3.4.2, rubocop-ast 1.32.3, analyzing as Ruby 2.7, running on ruby 3.3.3) [arm64-darwin23]
  - rubocop-minitest 0.34.5
  - rubocop-performance 1.22.1
  - rubocop-rails 2.23.1

[drsharp]

Hmmm... after a bit more poking around I realized that Style/RedundantRegexpEscape deals with the redundancy.

The issue is that it's run after Style/RedundantRegexpArgument and thus doesn't fix it right. If I start with:

#!/usr/bin/env ruby
test_value = 'something with "quotes" around it'
gsub_value = test_value.gsub(/\"/, """)

puts "Test Value: #{test_value.inspect}"
puts "Gsub Value: #{gsub_value.inspect}"

And run:

♯ rubocop test.rb --autocorrect --only Style/RedundantRegexpEscape                              
Inspecting 1 file
C

Offenses:

test.rb:3:31: C: [Corrected] Style/RedundantRegexpEscape: Redundant escape inside regexp literal
gsub_value = test_value.gsub(/\"/, """)
                              ^^

1 file inspected, 1 offense detected, 1 offense corrected

it corrects that line to be:

gsub_value = test_value.gsub(/"/, """)

(removing the redundant \)

And then if I run:

♯ rubocop test.rb --autocorrect --only Style/RedundantRegexpArgument                      
Inspecting 1 file
C

Offenses:

test.rb:3:30: C: [Corrected] Style/RedundantRegexpArgument: Use string '"' as argument instead of regexp /"/.
gsub_value = test_value.gsub(/"/, """)
                             ^^^

1 file inspected, 1 offense detected, 1 offense corrected

It properly corrects it to now be:

gsub_value = test_value.gsub('"', """)

So I don't know if the best way to deal with this is to add a fix to Style/RedundantRegexpArgument to handle the unusual case of the redundant escape (I can put a PR together for that) or to just make some note of this somewhere. It's definitely a corner case, but it "bit" us when it didn't properly handle this.

If there is an ordering to the cops, maybe Style/RedundantRegexpEscape needs to be run before Style/RedundantRegexpArgument?

[Earlopain]

Great investigative work! Issues where autocorrect from one cop steps on the toes of another crop up every once in a while.

The solution will be to declare them incompatible so that they happen in two passes. You can check out #13369 as a template if you want to make a PR yourself.

[Mohammed-Alanazisa]

We discovered a strange corner-case where a gsub that includes an unnecessarily-escaped double-quote gets autocorrected in a way that affects the gsub. I believe this is an anomaly because Ruby handles /"/ and /\"/ the same way... that is: the extra back-slash is extraneous but the Rubocop rule doesn't handle it as such.

Ruby apparently treats these the same:

irb(main):006:0> "one \" two".gsub(/"/, 'X')
=> "one X two"
irb(main):007:0> "one \" two".gsub(/\"/, 'X')
=> "one X two"

Expected behavior

When passed through Style/RedundantRegexpArgument and autocorrected the following line:

"an escaped \"double-quote\" value".gsub(/\"/, """)

should turn into:

"an escaped \"double-quote\" value".gsub('"', """)

both lines run as normal Ruby output the gsub the same way:

♯ irb
irb(main):001:0> "an escaped \"double-quote\" value".gsub(/\"/, """)
=> "an escaped "double-quote" value"
irb(main):002:0> "an escaped \"double-quote\" value".gsub('"', """)
=> "an escaped "double-quote" value"

Actual behavior

"an escaped \"double-quote\" value".gsub(/\"/, """)

becomes instead:

"an escaped \"double-quote\" value".gsub('\"', """)

(the \ is left in there). And that doesn't process the input string the same way:

irb(main):003:0> "an escaped \"double-quote\" value".gsub('\"', """)
=> "an escaped \"double-quote\" value"

Steps to reproduce the problem

I just created a simple test.rb file with this in it:

#!/usr/bin/env ruby
test_value = 'something with "quotes" around it'
gsub_value = test_value.gsub(/\"/, """)

puts "Test Value: #{test_value.inspect}"
puts "Gsub Value: #{gsub_value.inspect}"

I verified it ran fine and the output was as expected:

♯ ruby test.rb
Test Value: "something with \"quotes\" around it"
Gsub Value: "something with "quotes" around it"

I then ran the rubocop with autocorrect:

♯ rubocop test.rb --autocorrect
Inspecting 1 file
C

Offenses:

test.rb:3:30: C: [Corrected] Style/RedundantRegexpArgument: Use string '\"' as argument instead of regexp /\"/.
gsub_value = test_value.gsub(/\"/, """)
                             ^^^^

which changed it to:

#!/usr/bin/env ruby
test_value = 'something with "quotes" around it'
gsub_value = test_value.gsub('\"', """)

puts "Test Value: #{test_value.inspect}"
puts "Gsub Value: #{gsub_value.inspect}"

But now that runs as:

♯ ruby test.rb                 
Test Value: "something with \"quotes\" around it"
Gsub Value: "something with \"quotes\" around it"

which means the gsub isn't working.

RuboCop version

I originally tested this on 1.64.1 as that is what we are using in our Ruby 2.7.6 main environment:

♯ rubocop -V
1.64.1 (using Parser 3.3.4.2, rubocop-ast 1.32.3, running on ruby 2.7.6) [arm64-darwin23]
  - rubocop-minitest 0.34.5
  - rubocop-performance 1.21.1
  - rubocop-rails 2.23.1

But I also tested it on the latest version in our Ruby 3.3.3 environment and can confirm it fails there as well:

♯ rubocop -V
1.68.0 (using Parser 3.3.4.2, rubocop-ast 1.32.3, analyzing as Ruby 2.7, running on ruby 3.3.3) [arm64-darwin23]
  - rubocop-minitest 0.34.5
  - rubocop-performance 1.22.1
  - rubocop-rails 2.23.1