Bug #12703: String.gsub returns unexpected results with numeric match characters

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 2.4.0dev (2016-08-25 trunk 56006)
• Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN

[nlaveck (Nathan LaVeck)]

I'm unable to prepend a backslash to numeric group matches using gsub

irb(main):053:0> "z'z".gsub(/(')/, '\\1')
=> "z'z"

Expected Result

=> "z\'z"

Adding an extra backslash gives me this:

irb(main):056:0> "z'z".gsub(/(')/, '\\\1')
=> "z\\1z"

Tested on Ruby version 2.4.0

[nlaveck (Nathan LaVeck)]

• ruby -v set to ruby 2.4.0dev (2016-08-25 trunk 56006)

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Rejected

What you want is "z'z".gsub(/(')/, '\\\\\1').
You need to escape twice, for a literal, and for gsub.