GNU bug report logs - #36474
Algorithm in electric-pair--unbalanced-strings-p unsuitable for CC Mode

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Alan Mackenzie <acm <at> muc.de>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#36474: closed (Algorithm in electric-pair--unbalanced-strings-p
 unsuitable for CC Mode)
Date: Mon, 08 Jul 2019 09:37:01 +0000

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Your message dated Mon, 8 Jul 2019 09:36:27 +0000
with message-id <20190708093627.GB4529 <at> ACM>
and subject line Re: bug#36474: Acknowledgement (Algorithm in electric-pair--unbalanced-strings-p unsuitable for CC Mode)
has caused the debbugs.gnu.org bug report #36474,
regarding Algorithm in electric-pair--unbalanced-strings-p unsuitable for CC Mode
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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36474: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=36474
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Alan Mackenzie <acm <at> muc.de>
To: João Távora <joaotavora <at> gmail.com>,
 bug-gnu-emacs <at> gnu.org
Subject: Algorithm in electric-pair--unbalanced-strings-p unsuitable for CC
 Mode
Date: Tue, 2 Jul 2019 13:16:32 +0000

Hello João and Emacs.

This is a follow up bug to bug #36423: 27.0.50; electric-pair-mode not
working properly depending of file content.

Start the Emacs master (up to date state as of 2019-07-02T14:30 +0000)
with emacs -Q, put the following in a C++ Mode buffer and enable
electric-pair-mode:

"foo\n

.  Type a " at the end of foo.  electric-pair-mode wrongly inserts two
"s.

Diagnosis: electric-pair--unbalanced-strings-p works after the (single)
newly typed " has been stripped from the buffer.  It attempts to
determine whether there are any open strings after the point of
insertion.  It does this by using parse-partial-sexp, and checks (nth 3
<result>) as evidence of an open string.

This does not work in CC Mode, since although there is an open string
marker (with a string fence syntax-table property on it) this is
"closed" (from parse-partial-sexp's point of view) by the string fence
property on the newline at the end of the line.
electric-pair--unbalanced-strings-p thus returns the wrong result.

A more suitable algorithm might look something like this: check whether
the newly inserted " has a string fence syntax-table text property.
(Its insertion will have already triggered the before- and
after-change-functions which set this property.)  If so, there is an
open string.  Of course, this only applies to CC Mode modes.

-- 
Alan Mackenzie (Nuremberg, Germany).

[Message part 3 (message/rfc822, inline)]

From: Alan Mackenzie <acm <at> muc.de>
To: 36474-done <at> debbugs.gnu.org
Subject: Re: bug#36474: Acknowledgement (Algorithm in
 electric-pair--unbalanced-strings-p unsuitable for CC Mode)
Date: Mon, 8 Jul 2019 09:36:27 +0000

The bug has been fixed in CC Mode.

On Tue, Jul 02, 2019 at 13:17:01 +0000, GNU bug Tracking System wrote:
> Thank you for filing a new bug report with debbugs.gnu.org.

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> -- 
> 36474: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=36474
> GNU Bug Tracking System
> Contact help-debbugs <at> gnu.org with problems

-- 
Alan Mackenzie (Nuremberg, Germany).

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