GNU bug report logs - #38111
27.0.50; globalized-minor-mode not enabled on get-buffer-create

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

From: Juri Linkov <juri <at> linkov.net>
To: bug-gnu-emacs <at> gnu.org
Subject: 27.0.50; globalized-minor-mode not enabled on get-buffer-create
Date: Thu, 07 Nov 2019 23:53:04 +0200

This looks like a bug.  I found this issue while using global-tab-line-mode,
but to confirm that it's unrelated to tab-line, this bug report uses another
globalized minor-mode global-display-fill-column-indicator-mode:

0. emacs -Q
1. M-x global-display-fill-column-indicator-mode RET
2. C-x b test1 RET
3. RET  ;; this inserts newline to show column indicator
        ;; that confirms this mode is enabled in the buffer

4. M-: (switch-to-buffer (get-buffer-create "test2")) RET
5. RET  ;; no column indicator, mode not enabled
6. C-h v display-fill-column-indicator-mode RET
   ;; confirms its value is nil

Message #8 received at 38111 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Juri Linkov <juri <at> linkov.net>
Cc: 38111 <at> debbugs.gnu.org
Subject: Re: bug#38111: 27.0.50;
 globalized-minor-mode not enabled on get-buffer-create
Date: Fri, 08 Nov 2019 11:50:03 +0200

> From: Juri Linkov <juri <at> linkov.net>
> Date: Thu, 07 Nov 2019 23:53:04 +0200
> 
> This looks like a bug.  I found this issue while using global-tab-line-mode,
> but to confirm that it's unrelated to tab-line, this bug report uses another
> globalized minor-mode global-display-fill-column-indicator-mode:
> 
> 0. emacs -Q
> 1. M-x global-display-fill-column-indicator-mode RET
> 2. C-x b test1 RET
> 3. RET  ;; this inserts newline to show column indicator
>         ;; that confirms this mode is enabled in the buffer
> 
> 4. M-: (switch-to-buffer (get-buffer-create "test2")) RET
> 5. RET  ;; no column indicator, mode not enabled
> 6. C-h v display-fill-column-indicator-mode RET
>    ;; confirms its value is nil

Sounds like globalized-minor-mode machinery sdomehow doesn't support
the latter method of creating a buffer?  Does the turn-on function of
the mode get called in that scenario?

Message #11 received at 38111 <at> debbugs.gnu.org (full text, mbox):

From: Juri Linkov <juri <at> linkov.net>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 38111 <at> debbugs.gnu.org
Subject: Re: bug#38111: 27.0.50; globalized-minor-mode not enabled on
 get-buffer-create
Date: Tue, 12 Nov 2019 22:33:35 +0200

tags 38111 + notabug
close 38111
quit

>> This looks like a bug.  I found this issue while using global-tab-line-mode,
>> but to confirm that it's unrelated to tab-line, this bug report uses another
>> globalized minor-mode global-display-fill-column-indicator-mode:
>>
>> 0. emacs -Q
>> 1. M-x global-display-fill-column-indicator-mode RET
>> 2. C-x b test1 RET
>> 3. RET  ;; this inserts newline to show column indicator
>>         ;; that confirms this mode is enabled in the buffer
>>
>> 4. M-: (switch-to-buffer (get-buffer-create "test2")) RET
>> 5. RET  ;; no column indicator, mode not enabled
>> 6. C-h v display-fill-column-indicator-mode RET
>>    ;; confirms its value is nil
>
> Sounds like globalized-minor-mode machinery sdomehow doesn't support
> the latter method of creating a buffer?  Does the turn-on function of
> the mode get called in that scenario?

'C-x b' (switch-to-buffer) uses ‘window-normalize-buffer-to-switch-to’
to call after 'get-buffer-create' explicitly:

  (set-buffer-major-mode buffer)

It seems this is not a problem in practice, since callers
can add set-buffer-major-mode, so closing.

Message #18 received at 38111 <at> debbugs.gnu.org (full text, mbox):

From: Phil Sainty <psainty <at> orcon.net.nz>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 38111 <at> debbugs.gnu.org, Juri Linkov <juri <at> linkov.net>
Subject: Re: bug#38111: 27.0.50; globalized-minor-mode not enabled on
 get-buffer-create
Date: Wed, 13 Nov 2019 11:42:07 +1300

On 2019-11-08 22:50, Eli Zaretskii wrote:
> Sounds like globalized-minor-mode machinery somehow doesn't support
> the latter method of creating a buffer?

Yep, globalized modes use `after-change-major-mode-hook' to call the
buffer-local minor mode, and that hook is not triggered in these cases
because, although new buffers are in `fundamental-mode' by default,
the `fundamental-mode' function is not actually called, and so no mode
change occurs.

I believe this has cropped up in past discussion, but I don't recall
where offhand.

I agree that it's surprising when you are expecting the global mode(s)
to be enabled (I first realised it when attempting to use a globalized
mode for my custom key bindings, and discovering they were not being
enabled in various buffers).

If this were changed then there *might* be undesirable consequences to
having lots of created-behind-the-scenes buffers suddenly doing things
they never did before.

If the current behaviour is kept, the documentation for globalized
modes and for creating buffers should probably say something about the
matter.


-Phil

Message #21 received at 38111 <at> debbugs.gnu.org (full text, mbox):

From: Juri Linkov <juri <at> linkov.net>
To: Phil Sainty <psainty <at> orcon.net.nz>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 38111 <at> debbugs.gnu.org
Subject: Re: bug#38111: 27.0.50; globalized-minor-mode not enabled on
 get-buffer-create
Date: Wed, 13 Nov 2019 23:12:29 +0200

>> Sounds like globalized-minor-mode machinery somehow doesn't support
>> the latter method of creating a buffer?
>
> Yep, globalized modes use `after-change-major-mode-hook' to call the
> buffer-local minor mode, and that hook is not triggered in these cases
> because, although new buffers are in `fundamental-mode' by default,
> the `fundamental-mode' function is not actually called, and so no mode
> change occurs.
>
> I believe this has cropped up in past discussion, but I don't recall
> where offhand.
>
> I agree that it's surprising when you are expecting the global mode(s)
> to be enabled (I first realised it when attempting to use a globalized
> mode for my custom key bindings, and discovering they were not being
> enabled in various buffers).
>
> If this were changed then there *might* be undesirable consequences to
> having lots of created-behind-the-scenes buffers suddenly doing things
> they never did before.
>
> If the current behaviour is kept, the documentation for globalized
> modes and for creating buffers should probably say something about the
> matter.

Thanks for referring to the documentation.  It already explains this in
(info "(elisp) Defining Minor Modes")

 -- Macro: define-globalized-minor-mode global-mode mode turn-on
          keyword-args... body...
...
     Globally enabling the mode also affects buffers subsequently
     created by visiting files, and buffers that use a major mode other
     than Fundamental mode; but it does not detect the creation of a new
     buffer in Fundamental mode.

Message #24 received at 38111 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Phil Sainty <psainty <at> orcon.net.nz>
Cc: 38111 <at> debbugs.gnu.org, juri <at> linkov.net
Subject: Re: bug#38111: 27.0.50; globalized-minor-mode not enabled on
 get-buffer-create
Date: Fri, 15 Nov 2019 11:02:10 +0200

> Date: Wed, 13 Nov 2019 11:42:07 +1300
> From: Phil Sainty <psainty <at> orcon.net.nz>
> Cc: Juri Linkov <juri <at> linkov.net>, 38111 <at> debbugs.gnu.org
> 
> If the current behaviour is kept, the documentation for globalized
> modes and for creating buffers should probably say something about the
> matter.

I think updating the documentation about this is indeed the way to go
in this case.

Thanks.

Message #27 received at 38111 <at> debbugs.gnu.org (full text, mbox):

From: Juri Linkov <juri <at> linkov.net>
To: Phil Sainty <psainty <at> orcon.net.nz>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 38111 <at> debbugs.gnu.org
Subject: Re: bug#38111: 27.0.50; globalized-minor-mode not enabled on
 get-buffer-create
Date: Sun, 08 Dec 2019 00:56:00 +0200

reopen 38111
tags 38111 - notabug
quit

>> Sounds like globalized-minor-mode machinery somehow doesn't support
>> the latter method of creating a buffer?
>
> Yep, globalized modes use `after-change-major-mode-hook' to call the
> buffer-local minor mode, and that hook is not triggered in these cases
> because, although new buffers are in `fundamental-mode' by default,
> the `fundamental-mode' function is not actually called, and so no mode
> change occurs.
>
> I believe this has cropped up in past discussion, but I don't recall
> where offhand.
>
> I agree that it's surprising when you are expecting the global mode(s)
> to be enabled (I first realised it when attempting to use a globalized
> mode for my custom key bindings, and discovering they were not being
> enabled in various buffers).
>
> If this were changed then there *might* be undesirable consequences to
> having lots of created-behind-the-scenes buffers suddenly doing things
> they never did before.

Actually that turned out to be a problem in practice, e.g. with this recipe:

0. emacs -Q
1. M-x global-display-fill-column-indicator-mode RET

2. M-& ls -la RET  ;; or any other command that produces enough lines
3. observe that the global mode is activated in the output buffer

4. M-! ls -la RET
5. the global mode is NOT activated in the output buffer

The difference between these two is that shell-command-on-region uses just

  (get-buffer-create "*Shell Command Output*")

and doesn't set its default fundamental-mode explicitly.

The following patch fixes this, but I'm still not sure if we need
to grep all occurrences of get-buffer-create and add set-buffer-major-mode
everywhere?

diff --git a/lisp/simple.el b/lisp/simple.el
index 67ddab3d34..1c4fdf9945 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -3925,6 +3926,7 @@ shell-command-on-region
         ;; replacing its entire contents.
         (let ((buffer (get-buffer-create
                        (or output-buffer "*Shell Command Output*"))))
+          (set-buffer-major-mode buffer)
           (unwind-protect
               (if (and (eq buffer (current-buffer))
                        (or (not shell-command-dont-erase-buffer)

Message #34 received at 38111 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Juri Linkov <juri <at> linkov.net>
Cc: psainty <at> orcon.net.nz, 38111 <at> debbugs.gnu.org
Subject: Re: bug#38111: 27.0.50; globalized-minor-mode not enabled on
 get-buffer-create
Date: Sun, 08 Dec 2019 18:54:55 +0200

> From: Juri Linkov <juri <at> linkov.net>
> Cc: Eli Zaretskii <eliz <at> gnu.org>,  38111 <at> debbugs.gnu.org
> Date: Sun, 08 Dec 2019 00:56:00 +0200
> 
> The following patch fixes this, but I'm still not sure if we need
> to grep all occurrences of get-buffer-create and add set-buffer-major-mode
> everywhere?

This is a problem with all globalized minor modes, right?

Message #37 received at 38111 <at> debbugs.gnu.org (full text, mbox):

From: Juri Linkov <juri <at> linkov.net>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: psainty <at> orcon.net.nz, 38111 <at> debbugs.gnu.org
Subject: Re: bug#38111: 27.0.50; globalized-minor-mode not enabled on
 get-buffer-create
Date: Mon, 09 Dec 2019 00:27:52 +0200

>> The following patch fixes this, but I'm still not sure if we need
>> to grep all occurrences of get-buffer-create and add set-buffer-major-mode
>> everywhere?
>
> This is a problem with all globalized minor modes, right?

Yes, with all globalized minor modes.

So I installed the patch that fixes this particular case,
and leaving this bug report open waiting for a more general solution.

Message #40 received at 38111 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Juri Linkov <juri <at> linkov.net>
Cc: psainty <at> orcon.net.nz, Eli Zaretskii <eliz <at> gnu.org>, 38111 <at> debbugs.gnu.org
Subject: Re: bug#38111: 27.0.50; globalized-minor-mode not enabled on
 get-buffer-create
Date: Sun, 20 Sep 2020 13:06:27 +0200

Juri Linkov <juri <at> linkov.net> writes:

>>> The following patch fixes this, but I'm still not sure if we need
>>> to grep all occurrences of get-buffer-create and add set-buffer-major-mode
>>> everywhere?
>>
>> This is a problem with all globalized minor modes, right?
>
> Yes, with all globalized minor modes.
>
> So I installed the patch that fixes this particular case,
> and leaving this bug report open waiting for a more general solution.

I don't think a general solution is really possible here.  We don't want
any get-buffer-create to run the globalised modes -- that would be slow
and awkward.  We only want those to run in buffers that users actually
end up using, and I think that's something the modes themselves must
somehow decide.

So I don't think there's any realistic progress to be made in this bug
report, and I'm closing it.

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

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