Issue #18797 has been updated by matz (Yukihiro Matsumoto). I thought it was marked as obsolete long time ago. I think it's time to make it obsolete, probably via the usual obsoleting process (i.e. adding warning first). Matz ---------------------------------------- Bug #18797: Third argument to Regexp.new is a bit broken https://bugs.ruby-lang.org/issues/18797#change-100662 * Author: janosch-x (Janosch Müller) * Status: Open * Priority: Normal * Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN ---------------------------------------- ## Situation 'n' or 'N' can be passed as a third argument to `Regexp.new`. However, the behavior is not the same as the literal `n`-flag or the `Regexp::NOENCODING` option, and it makes the `#encoding` of `Regexp` and `Regexp#source` diverge: ```ruby /😅/n # => SyntaxError Regexp.new('😅', Regexp::NOENCODING) # => RegexpError re = Regexp.new('😅', nil, 'n') # => /😅/ re.options == Regexp::NOENCODING # => true re.encoding # => ASCII-8BIT re.source.encoding # => UTF-8 re =~ '😅' # => Encoding::CompatibilityError ``` ## Code [Here](https://github.com/ruby/ruby/blob/b41de3a1e8c36a5cc336b6f7cd3cb71126cf1a60/r...). There is also a test for the resulting encoding [here](https://github.com/ruby/ruby/blob/cf2bbcfff2985c116552967c7c4522f4630f2d18/t...), but it is a no-op because the whole file is set to that encoding via magic comment anyway. The third argument was added when ASCII was still the default Ruby encoding, so I guess Regexp and source encoding still matched at that point. ## Solution It could be fixed, but my impression is that it is not useful anymore. It was probably only added because `Regexp::NOENCODING` wasn't available at the time, so I think it could be deprecated like so:

Passing a third argument to Regexp.new is deprecated. Use `Regexp::NOENCODING` as second argument instead.

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