GNU bug report logs - #79409
31.0.50; project.el uses define-completion-category but depends on 26.1

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

From: Daniel Mendler <mail <at> daniel-mendler.de>
To: bug-gnu-emacs <at> gnu.org
Subject: 31.0.50; project.el uses define-completion-category but depends on
 26.1
Date: Mon, 08 Sep 2025 15:49:49 +0200

Since a few days ago project.el uses define-completion-category which is
not yet available on old Emacs versions. project.el is published on ELPA
and depends on Emacs 26.1.

See also https://old.reddit.com/r/emacs/comments/1nblwbl/suddenly_everything_wants_definecompletioncategory/

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

From: Eshel Yaron <me <at> eshelyaron.com>
To: Daniel Mendler via "Bug reports for GNU Emacs, the Swiss army knife of
 text editors" <bug-gnu-emacs <at> gnu.org>
Cc: Daniel Mendler <mail <at> daniel-mendler.de>, 79409 <at> debbugs.gnu.org,
 Dmitry Gutov <dmitry <at> gutov.dev>
Subject: Re: bug#79409: 31.0.50; project.el uses define-completion-category
 but depends on 26.1
Date: Mon, 08 Sep 2025 18:07:25 +0200

Daniel Mendler writes:

> Since a few days ago project.el uses define-completion-category which is
> not yet available on old Emacs versions. project.el is published on ELPA
> and depends on Emacs 26.1.

Right, thanks, should now be fixed on master (with commit 6b6cfa8e40b).

Eshel

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

From: Daniel Mendler <mail <at> daniel-mendler.de>
To: Eshel Yaron <me <at> eshelyaron.com>
Cc: Dmitry Gutov <dmitry <at> gutov.dev>,
 "Daniel Mendler via Bug reports for GNU Emacs, the Swiss army knife of
 text editors" <bug-gnu-emacs <at> gnu.org>, 79409 <at> debbugs.gnu.org
Subject: Re: bug#79409: 31.0.50; project.el uses define-completion-category
 but depends on 26.1
Date: Mon, 08 Sep 2025 18:18:59 +0200

Eshel Yaron <me <at> eshelyaron.com> writes:

> Daniel Mendler writes:
>
>> Since a few days ago project.el uses define-completion-category which is
>> not yet available on old Emacs versions. project.el is published on ELPA
>> and depends on Emacs 26.1.
>
> Right, thanks, should now be fixed on master (with commit 6b6cfa8e40b).

Thanks, I didn't see that you've already sent a mail to devel a short
while before my report. I wonder if some fallback code is needed, such
that project-buffer is treated like the buffer completion category on
older Emacs versions?

Daniel

Message #20 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Eshel Yaron <me <at> eshelyaron.com>
To: Daniel Mendler <mail <at> daniel-mendler.de>
Cc: Dmitry Gutov <dmitry <at> gutov.dev>,
 "Daniel Mendler via Bug reports for GNU Emacs, the Swiss army knife of
 text editors" <bug-gnu-emacs <at> gnu.org>, 79409 <at> debbugs.gnu.org
Subject: Re: bug#79409: 31.0.50; project.el uses define-completion-category
 but depends on 26.1
Date: Mon, 08 Sep 2025 20:08:51 +0200

Daniel Mendler <mail <at> daniel-mendler.de> writes:

> Eshel Yaron <me <at> eshelyaron.com> writes:
>
>> Daniel Mendler writes:
>>
>>> Since a few days ago project.el uses define-completion-category which is
>>> not yet available on old Emacs versions. project.el is published on ELPA
>>> and depends on Emacs 26.1.
>>
>> Right, thanks, should now be fixed on master (with commit 6b6cfa8e40b).
>
> Thanks, I didn't see that you've already sent a mail to devel a short
> while before my report. I wonder if some fallback code is needed, such
> that project-buffer is treated like the buffer completion category on
> older Emacs versions?

I thought about that, and it seems like a good idea.
IIUC, there was no such arrangement in Dmitry's introduction of the
project-buffer category though, so I'll leave that to him.

Regards,
Eshel

Message #26 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dmitry <at> gutov.dev>
To: Daniel Mendler <mail <at> daniel-mendler.de>, Eshel Yaron <me <at> eshelyaron.com>
Cc: "Daniel Mendler via Bug reports for GNU Emacs,
 the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org>,
 79409 <at> debbugs.gnu.org
Subject: Re: bug#79409: 31.0.50; project.el uses define-completion-category
 but depends on 26.1
Date: Mon, 8 Sep 2025 22:01:03 +0300

On 08/09/2025 19:18, Daniel Mendler wrote:
> Eshel Yaron<me <at> eshelyaron.com> writes:
> 
>> Daniel Mendler writes:
>>
>>> Since a few days ago project.el uses define-completion-category which is
>>> not yet available on old Emacs versions. project.el is published on ELPA
>>> and depends on Emacs 26.1.
>> Right, thanks, should now be fixed on master (with commit 6b6cfa8e40b).
> Thanks, I didn't see that you've already sent a mail to devel a short
> while before my report. I wonder if some fallback code is needed, such
> that project-buffer is treated like the buffer completion category on
> older Emacs versions?

Thanks for the report.

I've asked what Stefan thinks about a fallback route in this case.

Maybe it would be a good use for the 'compat' dependency, in addition to 
the FR in bug#79327.

Message #32 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Daniel Mendler <mail <at> daniel-mendler.de>
To: Dmitry Gutov <dmitry <at> gutov.dev>
Cc: "Daniel Mendler via Bug reports for GNU Emacs,
 the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org>,
 Eshel Yaron <me <at> eshelyaron.com>, 79409 <at> debbugs.gnu.org
Subject: Re: bug#79409: 31.0.50; project.el uses define-completion-category
 but depends on 26.1
Date: Mon, 08 Sep 2025 21:19:18 +0200

Dmitry Gutov <dmitry <at> gutov.dev> writes:

> On 08/09/2025 19:18, Daniel Mendler wrote:
>> Eshel Yaron<me <at> eshelyaron.com> writes:
>> 
>>> Daniel Mendler writes:
>>>
>>>> Since a few days ago project.el uses define-completion-category which is
>>>> not yet available on old Emacs versions. project.el is published on ELPA
>>>> and depends on Emacs 26.1.
>>> Right, thanks, should now be fixed on master (with commit 6b6cfa8e40b).
>> Thanks, I didn't see that you've already sent a mail to devel a short
>> while before my report. I wonder if some fallback code is needed, such
>> that project-buffer is treated like the buffer completion category on
>> older Emacs versions?
>
> Thanks for the report.
>
> I've asked what Stefan thinks about a fallback route in this case.
>
> Maybe it would be a good use for the 'compat' dependency, in addition to the FR
> in bug#79327.

I don't think we can use Compat here, since we cannot replace the
completion-metadata-get function such that callers magically learn about
category inheritance. We could provide a poor implementation for
define-completion-category which either does nothing or which copies the
completion category overrides and defaults from the parent to the
inherited category, but as such would behave differently than the new
mechanism. Neither is a satisfactory solution.

(buffer-match-p from the other bug report has been ported back, so this
can be used.)

Daniel

Message #38 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dmitry <at> gutov.dev>
To: Daniel Mendler <mail <at> daniel-mendler.de>
Cc: "Daniel Mendler via Bug reports for GNU Emacs,
 the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org>,
 Eshel Yaron <me <at> eshelyaron.com>, Stefan Monnier <monnier <at> IRO.UMontreal.CA>,
 79409 <at> debbugs.gnu.org
Subject: Re: bug#79409: 31.0.50; project.el uses define-completion-category
 but depends on 26.1
Date: Mon, 8 Sep 2025 22:23:42 +0300

On 08/09/2025 22:19, Daniel Mendler wrote:
> I don't think we can use Compat here, since we cannot replace the
> completion-metadata-get function such that callers magically learn about
> category inheritance.

Huh, right.

I guess Compat could do that with advice and such, but that way lies 
trouble.

> We could provide a poor implementation for
> define-completion-category which either does nothing or which copies the
> completion category overrides and defaults from the parent to the
> inherited category, but as such would behave differently than the new
> mechanism. Neither is a satisfactory solution.

That probably means there's little point for project.el to add any 
shims. Thanks.

Message #44 received at 79409 <at> debbugs.gnu.org (full text, mbox):

From: Daniel Mendler <mail <at> daniel-mendler.de>
To: Dmitry Gutov <dmitry <at> gutov.dev>
Cc: "Daniel Mendler via Bug reports for GNU Emacs,
 the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org>,
 Eshel Yaron <me <at> eshelyaron.com>, Stefan Monnier <monnier <at> IRO.UMontreal.CA>,
 79409 <at> debbugs.gnu.org
Subject: Re: bug#79409: 31.0.50; project.el uses define-completion-category
 but depends on 26.1
Date: Mon, 08 Sep 2025 21:41:38 +0200

Dmitry Gutov <dmitry <at> gutov.dev> writes:

> On 08/09/2025 22:19, Daniel Mendler wrote:
>> I don't think we can use Compat here, since we cannot replace the
>> completion-metadata-get function such that callers magically learn about
>> category inheritance.
>
> Huh, right.
>
> I guess Compat could do that with advice and such, but that way lies trouble.

Yes, we've excluded advices early on during the development of Compat.

>> We could provide a poor implementation for
>> define-completion-category which either does nothing or which copies the
>> completion category overrides and defaults from the parent to the
>> inherited category, but as such would behave differently than the new
>> mechanism. Neither is a satisfactory solution.
>
> That probably means there's little point for project.el to add any shims.
> Thanks.

You could add a project-buffer category to completion-category-defaults
to give the same effect as category inheritance as long as the user
doesn't override the settings.

Otoh you could also just leave things as is. This is not a big deal,
since it will just result in a minor difference in completion styles
settings and users could always override if they bother.

Daniel

Message #50 received at 79409 <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dmitry <at> gutov.dev>
To: Daniel Mendler <mail <at> daniel-mendler.de>
Cc: "Daniel Mendler via Bug reports for GNU Emacs,
 the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org>,
 Eshel Yaron <me <at> eshelyaron.com>, Stefan Monnier <monnier <at> IRO.UMontreal.CA>,
 79409 <at> debbugs.gnu.org
Subject: Re: bug#79409: 31.0.50; project.el uses define-completion-category
 but depends on 26.1
Date: Mon, 8 Sep 2025 23:17:43 +0300

On 08/09/2025 22:41, Daniel Mendler wrote:

> You could add a project-buffer category to completion-category-defaults
> to give the same effect as category inheritance as long as the user
> doesn't override the settings.

I suppose you mean like this. Seems like an improvement, since the 
original commit only added the entry in the latest Emacs.

diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index c15148110a6..2291b2a6b4c 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -1718,9 +1718,11 @@ project--buffers-completion-table
      (t
       (complete-with-action action buffers string pred)))))

-(when (fboundp 'define-completion-category) ; Introduced in Emacs 31.
-  (define-completion-category 'project-buffer '(buffer)
-    "Completion category for buffers in a given project."))
+(if (fboundp 'define-completion-category) ; Introduced in Emacs 31.
+    (define-completion-category 'project-buffer '(buffer)
+      "Completion category for buffers in a given project.")
+  (add-to-list 'completion-category-defaults
+               '(project-buffer (styles . (basic substring)))))

 (defun project--read-project-buffer ()
   (let* ((pr (project-current t))

Or - the reverse - project--buffers-completion-table could switch to the 
category 'buffer' in older Emacs.

> Otoh you could also just leave things as is. This is not a big deal,
> since it will just result in a minor difference in completion styles
> settings and users could always override if they bother.

Maybe not a big deal indeed.

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