bug#66554: [PATCH] Add the public API of Compat to the core

[Daniel Mendler via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Philip Kaludercic <philipk@posteo.net> writes:
>>> If I am not mistaken, all we would have to do is to adjust the version
>>> number in the patch to the current Emacs version -- and update it
>>> whenever Emacs is updated.  I have a slight concern that this could be
>>> easily forgotten, if it isn't hooked into some update scripts.
>>
>> Okay, I see. The specified version should probably be something like
>> 30.1.999 to make sure that packages requiring any Compat 30.1.x version
>> will not download the ELPA package?
>
> Because of 
>
>   (version< "30.1" "30.1.1")
>
> we can just set it to the actual Emacs version.

No. We want a version larger than any Compat version corresponding to
the current Emacs version. For example when there is compat-31.1.1.7 on
ELPA and Magit depends on compat>=31.1 and Magit is installed on an
Emacs 31.1, Compat should not be installed, since the builtin Compat
already satisfies the dependency. However if Magit is installed on an
Emacs 30.2, compat-31.1.1.7 should be installed. This means the internal
Compat version on Emacs 30.1 should be like 30.1.9999, or another large
enough version.

>> Is there a place where we could add a warning to make sure that
>> bumping the version won't be forgotten?
>
> I think that admin/admin.el's `set-version' could be used like this:
>
>> I don't mind, but it sounds like the details of adding compat.el to
>> core are not yet clear to all, and are still being discussed.  Also,
>> it sounds like we would need to modify compat.el for every release or
>> something? if so, this should be in make-tarball.txt.
>
> As mentioned above, I think this could be automated.

I agree, it would be good to automate the version bump, such that it
cannot be forgotten.

>> It might be also a good idea to mention this in the ELisp manual
>> somewhere.
>
> This being "Compat"?

It makes sense to also mention Compat in the Elisp manual and refer to
the Compat manual on ELPA. There we already document Compat usage for
Emacs core packages, which should be updated accordingly
(https://elpa.gnu.org/packages/doc/compat.html#Usage).

Daniel