GNU bug report logs - #37856
27.0.50; 'next-error' advised with 'recenter' signals error when run from "*grep*" buffer

Previous Next

To add a comment to this bug, you must first unarchive it, by sending
a message to control AT debbugs.gnu.org, with unarchive 37856 in the body.
You can then email your comments to 37856 AT debbugs.gnu.org in the normal way.

Toggle the display of automated, internal messages from the tracker.

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

From: Stefan Kangas <stefan <at> marxist.se>
To: bug-gnu-emacs <at> gnu.org
Subject: 27.0.50; 'next-error' advised with 'recenter' signals error when run
 from "*grep*" buffer
Date: Mon, 21 Oct 2019 20:38:47 +0200

I get an error when advising 'next-error' with 'recenter'.

Steps to reproduce:
1. Under "emacs -Q", evaluate:
    (defun my-advice (&rest args)
      (recenter))
    (advice-add 'next-error :after #'my-advice)
2. M-x rgrep RET [... grep for something]
3. Run 'next-error' (M-g M-n) from the "*grep*" buffer.

Result: I get the error:
    recenter-top-bottom: ‘recenter’ing a window that does not display
current-buffer.

(I also get the error when I run it in the second window when
'next-error' would take you to a different file.)

Expected result: I get no error.

---

Backtrace:
Debugger entered--Lisp error: (error "‘recenter’ing a window that does
not display curre...")
  recenter()
  my-advice(nil)
  apply(my-advice nil)
  next-error(nil)
  funcall-interactively(next-error nil)
  #<subr call-interactively>(next-error nil nil)
  apply(#<subr call-interactively> next-error (nil nil))
  call-interactively <at> ido-cr+-record-current-command(#<subr
call-interactively> next-error nil nil)
  apply(call-interactively <at> ido-cr+-record-current-command #<subr
call-interactively> (next-error nil nil))
  call-interactively(next-error nil nil)
  command-execute(next-error)

---

This seems to be due to this code in window.c:

  /* For reasons why we signal an error here, see
     https://lists.gnu.org/r/emacs-devel/2014-06/msg00053.html,
     https://lists.gnu.org/r/emacs-devel/2014-06/msg00094.html.  */
  if (buf != current_buffer)
    error ("`recenter'ing a window that does not display current-buffer.");

This code was added here:
3da983f8c4 2014-06-06 Stefan Monnier * src/window.c (Frecenter):
Signal an error if window-buffer is not current-buffer.

---

In GNU Emacs 27.0.50 (build 1, x86_64-apple-darwin17.7.0, NS
appkit-1561.61 Version 10.13.6 (Build 17G8037))
 of 2019-10-21 built on Stefans-MBP
Repository revision: 0e6f4628d8fff53505e4399e71da9f531a64fff7
Repository branch: master
Windowing system distributor 'Apple', version 10.3.1561
System Description:  Mac OS X 10.13.6

Message #8 received at 37856 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Stefan Kangas <stefan <at> marxist.se>
Cc: 37856 <at> debbugs.gnu.org
Subject: Re: bug#37856: 27.0.50;
 'next-error' advised with 'recenter' signals error when run from
 "*grep*" buffer
Date: Mon, 21 Oct 2019 22:30:42 +0300

> From: Stefan Kangas <stefan <at> marxist.se>
> Date: Mon, 21 Oct 2019 20:38:47 +0200
> 
> 1. Under "emacs -Q", evaluate:
>     (defun my-advice (&rest args)
>       (recenter))
>     (advice-add 'next-error :after #'my-advice)
> 2. M-x rgrep RET [... grep for something]
> 3. Run 'next-error' (M-g M-n) from the "*grep*" buffer.
> 
> Result: I get the error:
>     recenter-top-bottom: ‘recenter’ing a window that does not display
> current-buffer.

Why isn't this a cockpit error: you force a function that happens to
switch buffers to recenter.  It's like you've added a call to
'recenter' in some arbitrary place in a random function: you are
responsible for that code, and if it does stuff that it shouldn't,
your code is wrong.  No?

> This seems to be due to this code in window.c:
> 
>   /* For reasons why we signal an error here, see
>      https://lists.gnu.org/r/emacs-devel/2014-06/msg00053.html,
>      https://lists.gnu.org/r/emacs-devel/2014-06/msg00094.html.  */
>   if (buf != current_buffer)
>     error ("`recenter'ing a window that does not display current-buffer.");

Yes, and that's on purpose, see the cited discussion.

Message #11 received at 37856 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Kangas <stefan <at> marxist.se>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 37856 <at> debbugs.gnu.org
Subject: Re: bug#37856: 27.0.50; 'next-error' advised with 'recenter' signals
 error when run from "*grep*" buffer
Date: Mon, 21 Oct 2019 22:11:50 +0200

Eli Zaretskii <eliz <at> gnu.org> writes:

> > 1. Under "emacs -Q", evaluate:
> >     (defun my-advice (&rest args)
> >       (recenter))
> >     (advice-add 'next-error :after #'my-advice)
> > 2. M-x rgrep RET [... grep for something]
> > 3. Run 'next-error' (M-g M-n) from the "*grep*" buffer.
> >
> > Result: I get the error:
> >     recenter-top-bottom: ‘recenter’ing a window that does not display
> > current-buffer.
>
> Why isn't this a cockpit error: you force a function that happens to
> switch buffers to recenter.  It's like you've added a call to
> 'recenter' in some arbitrary place in a random function: you are
> responsible for that code, and if it does stuff that it shouldn't,
> your code is wrong.  No?

In this case my expectation was that this code would be run *after*
the command, i.e. when it had already done all the switching.  I'm not
sure that's comparable to placing recenter in an arbitrary place
inside the function.

It was surprising to me that this didn't work, and it's not clear what
I should do instead.  For example, the following code exhibits the
same problem:

(defun my-next-error ()
  (interactive)
  (next-error)
  (recenter))

What am I missing?

Best regards,
Stefan Kangas

Message #14 received at 37856 <at> debbugs.gnu.org (full text, mbox):

From: Juanma Barranquero <lekktu <at> gmail.com>
To: Stefan Kangas <stefan <at> marxist.se>
Cc: 37856 <at> debbugs.gnu.org, Eli Zaretskii <eliz <at> gnu.org>
Subject: Re: bug#37856: 27.0.50; 'next-error' advised with 'recenter' signals
 error when run from "*grep*" buffer
Date: Mon, 21 Oct 2019 23:37:22 +0200

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

On Mon, Oct 21, 2019 at 10:13 PM Stefan Kangas <stefan <at> marxist.se> wrote:

> (defun my-next-error ()
>   (interactive)
>   (next-error)
>   (recenter))
>
> What am I missing?

What's wrong with

  (add-hook 'next-error-hook 'recenter)

?

[Message part 2 (text/html, inline)]

Message #19 received at 37856-done <at> debbugs.gnu.org (full text, mbox):

From: Stefan Kangas <stefan <at> marxist.se>
To: Juanma Barranquero <lekktu <at> gmail.com>
Cc: 37856-done <at> debbugs.gnu.org, Eli Zaretskii <eliz <at> gnu.org>
Subject: Re: bug#37856: 27.0.50; 'next-error' advised with 'recenter' signals
 error when run from "*grep*" buffer
Date: Tue, 22 Oct 2019 00:19:13 +0200

Juanma Barranquero <lekktu <at> gmail.com> writes:

> > What am I missing?
>
> What's wrong with
>
>   (add-hook 'next-error-hook 'recenter)

Oops, how silly of me.  Yes, I'll just use that.  Thanks.

I'm still a bit confounded by the above behaviour, but if everyone
else feels that everything is in order I'll just go ahead and close
this.  Sorry about the noise.

Best regards,
Stefan Kangas

Message #22 received at 37856 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Stefan Kangas <stefan <at> marxist.se>
Cc: 37856 <at> debbugs.gnu.org
Subject: Re: bug#37856: 27.0.50; 'next-error' advised with 'recenter' signals
 error when run from "*grep*" buffer
Date: Tue, 22 Oct 2019 05:28:07 +0300

> From: Stefan Kangas <stefan <at> marxist.se>
> Date: Mon, 21 Oct 2019 22:11:50 +0200
> Cc: 37856 <at> debbugs.gnu.org
> 
> It was surprising to me that this didn't work, and it's not clear what
> I should do instead.  For example, the following code exhibits the
> same problem:
> 
> (defun my-next-error ()
>   (interactive)
>   (next-error)
>   (recenter))
> 
> What am I missing?

The advice effectively "injects" your code into the advised function,
just before it returns.

Message #25 received at 37856 <at> debbugs.gnu.org (full text, mbox):

From: Robert Pluim <rpluim <at> gmail.com>
To: 37856 <at> debbugs.gnu.org
Cc: stefan <at> marxist.se
Subject: Re: bug#37856: 27.0.50; 'next-error' advised with 'recenter'
 signals error when run from "*grep*" buffer
Date: Tue, 22 Oct 2019 09:56:14 +0200

>>>>> On Tue, 22 Oct 2019 00:19:13 +0200, Stefan Kangas <stefan <at> marxist.se> said:

    Stefan> Juanma Barranquero <lekktu <at> gmail.com> writes:
    >> > What am I missing?
    >> 
    >> What's wrong with
    >> 
    >> (add-hook 'next-error-hook 'recenter)

    Stefan> Oops, how silly of me.  Yes, I'll just use that.  Thanks.

    Stefan> I'm still a bit confounded by the above behaviour, but if everyone
    Stefan> else feels that everything is in order I'll just go ahead and close
    Stefan> this.  Sorry about the noise.

The add-function docstring says:

    Add a piece of advice on the function stored at PLACE.
    FUNCTION describes the code to add.  WHERE describes where to add it.
    WHERE can be explained by showing the resulting new function, as the
    result of combining FUNCTION and the previous value of PLACE, which we
    call OLDFUN here:
    `:before'	(lambda (&rest r) (apply FUNCTION r) (apply OLDFUN r))
    `:after'	(lambda (&rest r) (prog1 (apply OLDFUN r) (apply FUNCTION r)))
    `:around'	(lambda (&rest r) (apply FUNCTION OLDFUN r))

so I think Iʼd agree with your expectations. Of course, you could use
:around and call 'next-error' yourself in your function (untested).

Robert

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.