crystal-lang
It's impossible to create a regex that is MULTILINE but not DOT_ALL
Bug Report
The expected behaviour when using a MULTILINE regex like #.*$ is that it will match a whole line that begins with #
Because crystal conflates MULTILINE and DOT_ALL, that regex will, when set to MULTILINE, match also any subsequent lines until the end of the file.
Regex.new("#.*$", Regex::Options::MULTILINE).match("# this should be matched\nthis shouldn't")
=> Regex::MatchData("# this should be matched\nthis shouldn't")
To keep backwards compatibility, the behaviour of MULTILINE in crystal should not be changed, but I propose a change that adds a new MULTILINE_ONLY flag that just doesn't set DOT_ALL when creating the underlying PCRE2 object.
Some previous discussion was here: https://github.com/crystal-lang/crystal/issues/8062
Indeed it's sad that DOTALL is bunched together with MULTILINE.
/(?m)#.*$/ achieves the desired behavior of just MULTILINE, by the way - confusingly it's totally different from /#.*$/m
