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

[Eli Zaretskii]

> From: Philip Kaludercic <philipk@posteo.net>
> Cc: mail@daniel-mendler.de,  66554@debbugs.gnu.org,  stefankangas@gmail.com,
>   monnier@iro.umontreal.ca
> Date: Tue, 06 Feb 2024 19:10:32 +0000
> 
> >> +@defmac compat-call fun &rest args
> >> +This macro calls the compatibility function @var{fun} with @var{args}.
> >> +Many functions provided by Compat can be called directly without this
> >> +macro.  However in the case where Compat provides an alternative
> >> +version of an existing function, the function call has to go through
> >> +@code{compat-call}.
> >> +@end defmac
> >
> > This description left me without understanding when I need to use
> > compat-call and when I can just call FUN.  Can you explain more?
> 
> The intention was for this paragraph to catch that case,
> 
>   However in the case where Compat provides an alternative version of an
>   existing function, the function call has to go through
>   @code{compat-call}.
> 
> though the real information is to be found in the Compat manual, where
> the functions that have to be called via compat-call are documented.
> 
> Should the above sentence be rephrased to give a general feeling for
> when this is the case
> 
>   However in the case where Compat provides an alternative version of an
>   existing function, the function call has to go through
>   @code{compat-call}.  This is the case when, for example the signature
>   changes between versions, preventing older versions of Emacs from
>   using optional arguments introduced in newer releases.
> 
> or should we just refer to the external manual?

Let me try to make my point more clear: I'd prefer that the reader
emerges from reading this description with a practical way of knowing
when to call the function directly and when to call it via
'compat-call'.  If that's not easy to understand, perhaps we should
tell that 'compat-call' should always be used, to avoid some rare
corner cases where a direct call will not do, and be done?