GNU bug report logs - #66554
[PATCH] Add the public API of Compat to the core

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Message #148 received at 66554 <at> debbugs.gnu.org (full text, mbox):

From: Philip Kaludercic <philipk <at> posteo.net>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: Daniel Mendler <mail <at> daniel-mendler.de>, stefankangas <at> gmail.com,
 monnier <at> iro.umontreal.ca, 66554 <at> debbugs.gnu.org
Subject: Re: bug#66554: [PATCH] Add the public API of Compat to the core
Date: Fri, 19 Jan 2024 16:44:06 +0000

Eli Zaretskii <eliz <at> gnu.org> writes:

>> From: Daniel Mendler <mail <at> daniel-mendler.de>
>> Cc: Philip Kaludercic <philipk <at> posteo.net>,  66554 <at> debbugs.gnu.org,
>>   monnier <at> iro.umontreal.ca,  stefankangas <at> gmail.com
>> Date: Thu, 18 Jan 2024 21:35:59 +0100
>> 
>> Eli Zaretskii <eliz <at> gnu.org> writes:
>> 
>> > I find the documentation of this arrangement still insufficient.  The
>> > way this stuff works (which required Daniel to write 150 lines of
>> > explanation) is mostly kept out of the written docs, so we'll have to
>> > rely on people's memory.  Can we document this machinery better?
>> 
>> I agree. Where do you suggest to add the documentation? My intention is
>> to update the Compat manual (of the Compat ELPA package) with a more
>> detailed explanation of the mechanism as soon as the compat.el file gets
>> added to the Emacs core. We may want to avoid to duplicate the
>> information, by keeping the documentation in the Emacs compat.el file
>> concise, referring mainly to the Compat manual.
>
> The Compat manual cannot be the only place, because the information
> I'm talking about should be aimed at the Emacs developers, so it must
> be part of Emacs.  I suggest to have it in the commentary in
> compat.el.

OK.

>> >> +** New package Compat
>> >> +The Compat package on GNU ELPA provides forwards-compatibility
>> >> +support, so that packages that still provide support for older
>> >
>> > I think this is known as "backward compatibility".
>> 
>> Compat allows packages to use APIs which are newer than the Emacs they
>> depend on. A package depending on ((emacs "27.1") (compat "29.1"))
>> relies on Emacs 27.1 as base line, but can use some APIs from 29.1,
>> specifically the ones provided by Compat. Is there a better and more
>> specific term for this than "forward compatibility"?
>
> How about
>
>   Compat allows packages written for newer Emacs version to still work
>   with older Emacs versions.

I think the danger here is that Compat cannot provide full compatibility
support (some features either too complex to maintain, too slow to
reproduce or requiring changes in the core), so the way you phrase it
sounds like more than is being delivered.

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