Bug #19639: Escaped newline literals in Regexp are ignored in extended / free-spacing mode

• Status: Feedback
• Assignee: -
• Target version: -
• ruby -v: ruby 3.2.0 (2022-12-25 revision a528908271) [arm64-darwin21]
• Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN

[janosch-x (Janosch Müller)]

When we want to match whitespace with a Regexp that uses the x-flag, we can do that with escaped literal whitespace:

' '[/\ /x] # => " "

This works for all whitespace - except newlines:

"\n"[/\
/x] # => ""

/\
/x.source # => ""

I guess another parsing step eliminates such escaped newlines before the regexp parsing happens?

It is probably a rare issue because most people prefer "\n" in Regexps over literal newlines, but at least the relevant statement in the documentation is a bit too broad as it is:

Use escaped whitespace such as \ , i.e. a space preceded by a backslash.

Maybe we want to add a caveat like (Does not work for newlines.)?

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Feedback

I don’t think it is a bug, because a backslash at the end of line is line concatenation and those two chars are dropped, in general.