Issue #4044 has been updated by Matthew Kerwin.


I want to write a spec for this, but some of the details are unclear to me. Can we confirm whether each of the following are spec?

~~~Ruby
RUBY_VERSION #=> "2.3.0"

# eszett (case conversion => multiple chars)
/\W/     =~ "\u00DF" #=> 0
/\W/i    =~ 'SS' #=> nil
/[\W]/i  =~ 'SS' #=> 0
/[^\W]/i =~ 'SS' #=> 0

# 'ff' ligature (case conversion => multiple chars)
/\W/     =~ "\uFB00" #=> 0
/\W/i    =~ 'FF' #=> nil
/[\W]/i  =~ 'FF' #=> 0
/[^\W]/i =~ 'FF' #=> 0

# Kelvin sign (case conversion => a single character)
/\W/     =~ "\u212A" #=> 0
/\W/i    =~ 'k'  #=> nil
/[\W]/i  =~ 'k'  #=> nil ??
/[^\W]/i =~ 'k'  #=> 0
~~~

Notably, in jruby:

~~~Ruby
RUBY_VERSION #=> "2.2.0"
/[\W]/i  =~ 'k'  #=> nil, not 0
/[^\W]/i =~ 'k'  #=> 0, not nil
/[^\W]/i =~ 'SS' #=> nil, not 0
~~~

----------------------------------------
Bug #4044: Regex matching errors when using \W character class and /i option
https://bugs.ruby-lang.org/issues/4044#change-56852

* Author: Ben Hoskings
* Status: Closed
* Priority: Normal
* Assignee: Yui NARUSE
* ruby -v: ruby 1.9.2p0 (2010-08-18 revision 29036) [x86_64-darwin10.4.0]
* Backport: 
----------------------------------------
=begin
 Hi all,
 
 Josh Bassett and I just discovered an issue with regex matches on ruby-1.9.2p0. (We reduced it while we were hacking on gemcutter.)
 
 The case-insensitive (/i) option together with the non-word character class (\W) match inconsistently against the alphabet. Specifically the regex doesn't match properly against the letters 'k' and 's'.
 
 The following expression demonstrates the problem in irb:
 
     puts ('a'..'z').to_a.map {|c| [c, c.ord, c[/[^\W]/i] ].inspect }
 
 As a reference, the following two expressions are working properly:
 
     puts ('a'..'z').to_a.map {|c| [c, c.ord, c[/[^\W]/] ].inspect }
     puts ('a'..'z').to_a.map {|c| [c, c.ord, c[/[\w]/i] ].inspect }
 
 Cheers
 Ben Hoskings & Josh Bassett
=end




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