GNU bug report logs - #23339
24.5; align-region assumes that match does not contain newline

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

From: Josh <josh+gnu <at> nispio.net>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.5; align-region assumes that match does not contain newline
Date: Thu, 21 Apr 2016 23:20:19 -0700

The align-region function assumes that a matching regexp does not
contain a newline.  This causes unexpected behavior in cases where the
first "column" being aligned contains only whitespace.  The following
script exhibits the unexpected behavior:

emacs -Q --eval '(progn
 (switch-to-buffer "*test*")
 (text-mode)
 (setq indent-tabs-mode nil)
 (insert "lorem ipsum, dolor sit amet,\n ,,\n")
 (let ((table (make-syntax-table (syntax-table))))
   ;; (modify-syntax-entry ?\n ">" table) ; <= UNCOMMENT THIS LINE TO FIX
   (with-syntax-table table
   (align-regexp (point-min) (point-max) "\\(\\s-*\\)," 1 1 t))))'

Uncommenting the seventh line and running again will show the expected
behavior.  The fix works around the problem by using a syntax map in
which the newline character does not belong to the whitespace syntax
class, thus preventing \s-* from matching the newline.


In GNU Emacs 24.5.1 (x86_64-apple-darwin13.4.0, NS apple-appkit-1265.21)
 of 2015-04-10 on builder10-9.porkrind.org
Windowing system distributor `Apple', version 10.3.1348
Configured using:
 `configure --with-ns '--enable-locallisppath=/Library/Application
 Support/Emacs/${version}/site-lisp:/Library/Application
 Support/Emacs/site-lisp''

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Message #8 received at 23339 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Josh <josh+gnu <at> nispio.net>
Cc: 23339 <at> debbugs.gnu.org
Subject: Re: bug#23339: 24.5; align-region assumes that match does not
 contain newline
Date: Wed, 02 Dec 2020 13:19:47 +0100

[Message part 1 (text/plain, inline)]

Josh <josh+gnu <at> nispio.net> writes:

> The align-region function assumes that a matching regexp does not
> contain a newline.  This causes unexpected behavior in cases where the
> first "column" being aligned contains only whitespace.  The following
> script exhibits the unexpected behavior:
>
> emacs -Q --eval '(progn
>  (switch-to-buffer "*test*")
>  (text-mode)
>  (setq indent-tabs-mode nil)
>  (insert "lorem ipsum, dolor sit amet,\n ,,\n")
>  (let ((table (make-syntax-table (syntax-table))))
>    ;; (modify-syntax-entry ?\n ">" table) ; <= UNCOMMENT THIS LINE TO FIX
>    (with-syntax-table table
>    (align-regexp (point-min) (point-max) "\\(\\s-*\\)," 1 1 t))))'
>
> Uncommenting the seventh line and running again will show the expected
> behavior.  The fix works around the problem by using a syntax map in
> which the newline character does not belong to the whitespace syntax
> class, thus preventing \s-* from matching the newline.

(This bug report unfortunately got no response at the time.)

You don't specify what the result is you're seeing, and what you expect
to see, so I'm not sure whether this is fixed or not.  When I try your
recipe in Emacs 26.1-28, I get:

[Message part 2 (image/png, inline)]

[Message part 3 (text/plain, inline)]

Which I think is correct behaviour?  

Are you still seeing buggy behaviour here in more recent Emacs versions?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #13 received at 23339 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Josh <josh+gnu <at> nispio.net>
Cc: 23339 <at> debbugs.gnu.org
Subject: Re: bug#23339: 24.5; align-region assumes that match does not
 contain newline
Date: Tue, 19 Jan 2021 08:32:24 +0100

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

> Are you still seeing buggy behaviour here in more recent Emacs versions?

More information was requested, but no response was given within a
month, so I'm closing this bug report.  If the problem still exists,
please respond to this email and we'll reopen the bug report.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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