[ruby-core:28256] [Feature #2759] Regexp /g and /G options

Issue #2759 has been updated by Michael Fellinger.


Given the following code in 1.8 with oniguruma gem, first without the flag:

Oniguruma::ORegexp.new('(?=([ ]{4}|\t)(?<marker>[-]([ ]{,2})\k<marker>))')
ArgumentError: Oniguruma Error: invalid backref number/name

Now with the flag:

Oniguruma::ORegexp.new('(?=([ ]{4}|\t)(?<marker>[-]([ ]{,2})\k<marker>))', :options => Oniguruma::OPTION_CAPTURE_GROUP)
# /(?=([ ]{4}|\t)(?<marker>[-]([ ]{,2})\k<marker>))/

It fails like this in 1.9, clearly the flag is needed:

/(?=([ ]{4}|\t)(?<marker>[-]([ ]{,2})\k<marker>))/
SyntaxError: (irb):3: invalid backref number/name: /(?=([ ]{4}|\t)(?<marker>[-]([ ]{,2})\k<marker>))/

This is an excerpt from a regular expression found in the Markdown syntax used by Textmate.
Textmate uses the Oniguruma C API directly, and uses this flag for the regular expressions it uses for syntax highlighting.
There are a couple of other regular expressions that I cannot process due to the lack of this flag, and the oniguruma gem is not easy to port to Ruby 1.9.
I've considered writing a FFI wrapper for the C API, but that would just duplicate all of the work already in Ruby core just for the addition of this flag, that is why I propose adding it to Ruby instead.
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http://redmine.ruby-lang.org/issues/show/2759

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