bug#58839: [Patch] Re: bug#58839: 29.0.50; project-kill-buffer fails when Eglot is running

[Philip Kaludercic]

Dmitry Gutov <dgutov@yandex.ru> writes:

> On 01.11.2022 13:27, Philip Kaludercic wrote:
>
>> I am biased, but I believe that the language could even find more use in
>> project.el, by having `project-buffers' just call `match-buffers' with a
>> special `buffer-match-p' predicate.  Here is a sketch of how that could
>> look like (I haven't tested it yet):
>
> Sure, but only after we're ready to drop project.el support for Emacs
> older than 29.

The functionality can be provided using Compat[0], as is already done for a
few core package that are distributed on GNU ELPA (ERC, python-mode).

[0] https://elpa.gnu.org/packages/compat.html

>> diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
>> index ac278edd40..b55c245368 100644
>> --- a/lisp/progmodes/project.el
>> +++ b/lisp/progmodes/project.el
>> @@ -352,15 +352,28 @@ project--remote-file-names
>>                   (concat remote-id file))
>>                 local-files))))
>>   +(defun project-includes-buffer-p (buffer dir)
>> +  "Return non-nil if the `default-directory' of BUFFER is below DIR."
>> +  (file-in-directory-p
>> +   (buffer-local-value 'default-directory buffer)
>> +   dir))
>
> Not an optimal name, given that we have made project-buffers a generic
> function, so that a custom project backend can define their own
> buffer-listing strategy. And this one implies that matching by
> default-directory is universal.

Right, as I said this is just a sketch.

But as the diff showed, I think any more specific implementation ought
to extend the generic implementation, by using `cl-call-next-method'
instead of `buffer-list'.

>> +(defcustom project-buffer-conditions
>
> Why not keep considering unknown buffers as part of project by default?

What are "unknown buffers"?

> We'll just stop killing them on cleanup.
>
> Otherwise, we'll really need an extensible mechanism for major modes
> all around the ecosystem to tag themselves as project-visible.

Wouldn't a simple buffer local variable suffice?

>> +  '(and (or buffer-file-name
>> +            (derived-mode . compilation-mode)
>> +            (derived-mode . dired-mode)
>> +            (derived-mode . diff-mode)
>> +            (derived-mode . comint-mode)
>> +            (derived-mode . eshell-mode)
>> +            (derived-mode . change-log-mode))
>> +        project-includes-buffer-p)
>> +  "A buffer predicate for matching what buffers belong to a project."
>> +  :type 'buffer-predicate)
>
> Let's not forget Xref, Occur, VC-Dir, Log-View. Maybe some others.

This is my point, I think João is right that this ought to be an
enumeration of major modes that are related to projects.  As this is a
user option, users can add or remove whatever modes they disagree on and
that behaviour would ideally be propagated to all projects.