bug#81550: 30.2; add project-specific hooks to unload-feature-special-hooks

Eli Zaretskii <[email protected]> writes:

>> From: Lin Jian <[email protected]>
>> Cc: [email protected],  [email protected]
>> Date: Tue, 04 Aug 2026 20:10:40 +0800
>> 
>> Eli Zaretskii <[email protected]> writes:
>> 
>> >> Cc: [email protected]
>> >> Date: Tue, 04 Aug 2026 15:28:33 +0800
>> >> From: Lin Jian via "Bug reports for GNU Emacs,
>> >>  the Swiss army knife of text editors" <[email protected]>
>> >> 
>> >> 
>> >> When supporting `unload-feature' for my project backend, I have to write
>> >> a FEATURE-unload-function to clean `project-find-functions' and
>> >> `project-list-exclude'.
>> >> 
>> >> That FEATURE-unload-function can be omitted if `project-find-functions'
>> >> and `project-list-exclude' are added to `unload-feature-special-hooks'.
>> >> I suggest adding them.
>> >
>> > Does it really happen frequently that unloading a feature affects
>> > which files project.el will consider, or is that a rare corner case?
>> 
>> If by "a feature" you mean a random feature, then probably that random
>> feature does not need to clean project-specific hooks.
>> 
>> However, note that I do not mean a random feature.  I mean specific
>> features: project backends.  See C-h P project RET for definition of
>> project backend.  These specific features always have to clean
>> project-specific hooks if they decide to support `unload-feature'.
>
> But unload-feature-special-hooks is a general hook, not limited to
> project backends, is it?  Or what am I missing?

To be clear, I am not arguing anything.  I just try to clarify things,
in case needed.

If, in your first reply, you said something like:

> Project backends are rare features so we should not add
> project-specific hooks to `unload-feature-special-hooks'.

Then I would find it clear and I would see no need to clarify it.