On Sat, Mar 25, 2023, 12:55 Eli Zaretskii <eliz@gnu.org> wrote:.

> >
> > So it is most clearly a regression.
>
> There's something missing in the above description, since
> buffer-match-p accepts a function as its CONDITION argument, and calls
> that function with the buffer and ACTION.  So it sounds like code
> written for Emacs 28 should still work.  What is missing here that
> explains the breakage?
>

As I highlighted, Emacs used to call such functions with a buffer _name_
and an action. Now it calls them with a buffer _object_ and an action. This
is a backward-incompatible change.

João