GNU bug report logs - #7882
24.0.50; Bad regexp for javascript regexps

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Harald Hanche-Olsen <hanche <at> math.ntnu.no>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.0.50; Bad regexp for javascript regexps
Date: Fri, 21 Jan 2011 18:50:29 +0100 (CET)

Put the following four line code snippet in a new buffer:

replace(/\\/g,something);
// Now we're in trouble:
// Still in trouble.
// And all's well again.

and activate js-mode and font-lock-mode.

The syntax colouring is now off: The code starting with the first
slash on the first line and ending with the first slash on the second
line is coloured as a regexp; now the syntax highlighter is unaware
that we are in a comment, and reads the single quote as the start of a
string. After the second single quote things return to normal.

The problem seems to lie with the constant js--regexp-literal declared
in js.el, as this regexp does not treat backslashes with sufficient care.

In GNU Emacs 24.0.50.1 (x86_64-apple-darwin10.5.0, NS apple-appkit-1038.35)
 of 2010-12-27 on mack
Windowing system distributor `Apple', version 10.3.1038
configured using `configure  '--with-ns''

- Harald

Message #10 received at 7882-done <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
To: Harald Hanche-Olsen <hanche <at> math.ntnu.no>
Cc: 7882-done <at> debbugs.gnu.org
Subject: Re: bug#7882: 24.0.50; Bad regexp for javascript regexps
Date: Fri, 21 Jan 2011 15:50:17 -0500

> replace(/\\/g,something);

Thanks, I've installed the patch below into the emacs-23 branch which
should fix this problem.  The highlighting is not reliable when the
regexp spans multiple lines, tho, so I wonder: are multi-line regexps
valid? common? important?


        Stefan

Message #13 received at 7882 <at> debbugs.gnu.org (full text, mbox):

From: Harald Hanche-Olsen <hanche <at> math.ntnu.no>
To: 7882 <at> debbugs.gnu.org, help-debbugs <at> gnu.org
Subject: Re: bug#7882: closed
Date: Fri, 21 Jan 2011 22:16:28 +0100 (CET)

I have no idea how common or important multiline regexps are in
javascript. As far as I am concerned, if it's difficult to match them
reliably, maybe one shouldn't even try. Though that has its own
dangers: Namely, stuff inside an unmatched regexp triggering
inappropriate syntax highlighting. So perhaps we should stick with
doing the best we can, anyhow.

- Harald

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