GNU bug report logs - #65797
`buffer-match-p` should not use `func-arity`

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From: Joseph Turner <joseph <at> breatheoutbreathe.in>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: Stefan Monnier <monnier <at> iro.umontreal.ca>, 65797 <at> debbugs.gnu.org
Subject: bug#65797: 29.0.92; func-arity should not return (0 . many) with apply-partially
Date: Mon, 11 Sep 2023 09:57:51 -0700

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

> I think one of the alternatives you proposed was backward-compatible
> (albeit not very elegant).  So my vote is for that alternative.

I'm in favor of the solution in the patch (from Stefan's suggestion):

> - Replace `&optional arg` with `&rest args` and pass those args via
>   `apply`, so the number of args passed doesn't depend on the function
>   but on the caller.

The "&rest args" solution is clean and hack-free. It breaks
compatibility, but in unlikely cases:

- CONDITION pred accepts only a buffer argument, but additional ARG was
  passed (why would you do this?)

- CONDITION pred accepts two arguments, and no ARG was passed (this code
  would be broken anyway, right?)

Since buffer-match-p is new in Emacs 29, is it acceptable to assume that
code affected by this breakage can be updated?

Joseph

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