GNU bug report logs - #5805
23.1; abbrev-insert does not protext itself with save-excursion

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: "Maguire, Andrew (GE Infra, Energy)" <andrew.maguire <at> ge.com>
Subject: bug#5805: closed (Re: bug#5805: 23.3 abbrev-insert needs a
 limited save-excursion)
Date: Fri, 08 Jul 2011 14:44:02 +0000

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

Your bug report

#5805: 23.1; abbrev-insert does not protext itself with save-excursion

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 5805 <at> debbugs.gnu.org.

-- 
5805: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=5805
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

[Message part 2 (message/rfc822, inline)]

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Bob Nnamtrop <bobnnamtrop <at> gmail.com>
Cc: 5805-done <at> debbugs.gnu.org
Subject: Re: bug#5805: 23.3 abbrev-insert needs a limited save-excursion
Date: Fri, 08 Jul 2011 10:43:18 -0400

> --- 23.3/abbrev.el      2011-07-07 08:16:16.000000000 -0600
> +++ 23.3.fix/abbrev.el  2011-07-07 08:43:24.000000000 -0600
> @@ -713,6 +713,7 @@
>      ;; If this abbrev has an expansion, delete the abbrev
>      ;; and insert the expansion.
>      (when (stringp (symbol-value abbrev))
> +      (save-excursion
>        (goto-char wordstart)
>        ;; Insert at beginning so that markers at the end (e.g. point)
>        ;; are preserved.
> @@ -741,7 +742,7 @@
>                (skip-syntax-forward "^w" (1- end))
>                ;; Change just that.
>                (upcase-initials-region (point) (1+ (point)))
> -              (goto-char end))))))
> +              (goto-char end)))))))
>      ;; Now point is at the end of the expansion and the beginning is
>      ;; in last-abbrev-location.

This can't be right, as can be seen in the comment right here: after
this (goto-char end), the rest of the code expects point to be "at the
end of the expansion".

I installed the ugly patch below instead.


        Stefan


=== modified file 'lisp/ChangeLog'
--- lisp/ChangeLog	2011-07-08 14:25:25 +0000
+++ lisp/ChangeLog	2011-07-08 14:41:48 +0000
@@ -5,6 +5,8 @@
 
 2011-07-08  Stefan Monnier  <monnier <at> iro.umontreal.ca>
 
+	* abbrev.el (expand-abbrev): Try to preserve point (bug#5805).
+
 	* vc/vc-bzr.el (vc-bzr-revision-keywords): Remove svn, it's only
 	provided by a particular plugin.
 

=== modified file 'lisp/abbrev.el'
--- lisp/abbrev.el	2011-07-05 15:31:22 +0000
+++ lisp/abbrev.el	2011-07-08 14:41:16 +0000
@@ -814,6 +814,8 @@
     (destructuring-bind (&optional sym name wordstart wordend)
         (abbrev--before-point)
       (when sym
+        (let ((startpos (copy-marker (point) t))
+              (endmark (copy-marker wordend t)))
         (unless (or ;; executing-kbd-macro
                  noninteractive
                  (window-minibuffer-p (selected-window)))
@@ -826,7 +828,14 @@
         (setq last-abbrev-location wordstart)
         ;; If this abbrev has an expansion, delete the abbrev
         ;; and insert the expansion.
-        (abbrev-insert sym name wordstart wordend)))))
+          (prog1
+              (abbrev-insert sym name wordstart wordend)
+            ;; Yuck!!  If expand-abbrev is called with point slightly
+            ;; further than the end of the abbrev, move point back to
+            ;; where it started.
+            (if (and (> startpos endmark)
+                     (= (point) endmark)) ;Obey skeletons that move point.
+                (goto-char startpos))))))))
 
 (defun unexpand-abbrev ()
   "Undo the expansion of the last abbrev that expanded.

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

From: "Maguire, Andrew (GE Infra, Energy)" <andrew.maguire <at> ge.com>
To: <bug-gnu-emacs <at> gnu.org>
Subject: RE: Returned mail: Cannot send message within 3 days
Date: Tue, 30 Mar 2010 18:33:07 +0200

Try again...

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Sent: 29 March 2010 13:07
To: andrewma <at> Smallworld.co.uk
Subject: Returned mail: Cannot send message within 3 days

The original message was received at Fri, 26 Mar 2010 12:06:32 +0100
(BST)
from shark [193.128.11.12]

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Return-Path: <andrewma <at> Smallworld.co.uk>
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Date: Fri, 26 Mar 2010 12:25:49 +0000
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From: andrew.maguire <at> ge.com
To: bug-gnu-emacs <at> gnu.org
Subject: 23.1; abbrev-insert does not protext itself with save-excursion
Reply-to: andrew.maguire <at> ge.com

I believe there is a regression/change of behaviour with the lisp
implementation
of the abbrev package compared with earlier Emacsen.

In our code we use abbrev to dynamically expand certain
keywords. However, the new lisp implementation is more
eager in finding things to check, ie. it is able to look back past
non-word characters to see if an abbrev is to be found.
In this situation it is essential to do save-excursion.

Ideally, either insert-abbrev should do a save-excursion itself or all
calls to it should.
In our code, expand-abbrev is call which internally calls abbrev-insert.

Alternatively, is it the recommendation for user code to surround all
"abbrev" calls with save-excursion now?

Thanks for you advice,
Andrwe Maguire


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