From: Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
To: Joseph Turner <joseph@breatheoutbreathe.in>
Cc: 65797@debbugs.gnu.org
Subject: bug#65797: 29.0.92; func-arity should not return (0 . many) with apply-partially
Date: Thu, 07 Sep 2023 11:50:16 -0400 [thread overview]
Message-ID: <jwvv8cmdmzz.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <87v8cmct9b.fsf@breatheoutbreathe.in> (Joseph Turner's message of "Thu, 07 Sep 2023 00:53:07 -0700")
retitle 65797 `buffer-match-p` should not use `func-arity`
thanks
> (match-buffers (apply-partially #'local-variable-p 'foo))
Note that this call is incorrect according to the docstring of
`buffer-match-p`, which says:
CONDITION is either:
[...]
- a predicate function that takes BUFFER-OR-NAME and ARG as
arguments, and returns non-nil if the buffer matches,
IOW, you have to pass a function that accepts 2 arguments, whereas your
(apply-partially #'local-variable-p 'foo) only accepts one.
The Texinfo docs instead say:
@item
A predicate function, which should return non-@code{nil} if the buffer
matches. If the function expects one argument, it is called with
@var{buffer-or-name} as the argument; if it expects 2 arguments, the
first argument is @var{buffer-or-name} and the second is @var{arg}
(or @code{nil} if @var{arg} is omitted).
but in general we can't reliably decide whether "the function expects
one argument", so we can't implement the above promise in a reliable way.
`apply-partially` is just one case where this shows up, but the problem
is much more general.
`buffer-match-p` uses the `func-arity` hack to try to make it work with
some functions of 1 argument, but it's just a hack.
We should get rid of this hack. Here are some possible replacements
(by order of my preference):
- 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.
- Always pass both args to the function (i.e. as documented in the
docstring).
- Get rid of `&optional arg` altogether.
AFAICT, most callers don't use it, but it's used for
`display-buffer-alist`, so it would have further consequences there :-(
- Use a hack like
(condition-case nil (funcall condition buffer-or-name arg)
(wrong-number-of-arguments (funcall condition buffer-or-name)))
which handles the arity mismatch a bit more reliably, but at the cost of
occasionally running the function twice.
Stefan
next prev parent reply other threads:[~2023-09-07 15:50 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-07 7:53 bug#65797: 29.0.92; func-arity should not return (0 . many) with apply-partially Joseph Turner via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-07 12:35 ` Mattias Engdegård
2023-09-07 15:11 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-07 15:17 ` Mattias Engdegård
2023-09-07 13:43 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-07 15:50 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors [this message]
2023-09-08 4:40 ` Joseph Turner via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-08 6:46 ` Eli Zaretskii
2023-09-08 15:52 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-08 16:37 ` Joseph Turner via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-08 17:18 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-08 18:16 ` Joseph Turner via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-08 18:20 ` Eli Zaretskii
2023-09-11 16:57 ` Joseph Turner via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-11 18:58 ` Eli Zaretskii
2023-09-12 18:30 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-08 17:01 ` bug#65797: `buffer-match-p` should not use `func-arity` Philip Kaludercic
2023-09-12 18:28 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-13 21:50 ` Philip Kaludercic
2023-09-14 13:47 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-18 9:12 ` Philip Kaludercic
2023-09-18 11:55 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-18 17:23 ` Philip Kaludercic
2023-09-18 18:05 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-19 8:34 ` Philip Kaludercic
2023-09-19 10:06 ` Dmitry Gutov
2023-09-19 13:56 ` Philip Kaludercic
2023-09-19 16:13 ` Dmitry Gutov
2023-10-08 9:10 ` Joseph Turner via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-10-08 10:25 ` Dmitry Gutov
2023-10-09 21:40 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-10-12 4:53 ` Joseph Turner via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-10-12 11:34 ` Dmitry Gutov
2023-10-13 15:57 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-10-14 6:13 ` Eli Zaretskii
2023-10-14 14:31 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-10-15 6:13 ` Eli Zaretskii
2023-10-16 16:33 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-10-16 20:16 ` Joseph Turner via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-10-19 12:18 ` Eli Zaretskii
2023-10-21 2:52 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-15 0:45 ` Dmitry Gutov
2023-09-15 1:38 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-15 16:38 ` Dmitry Gutov
2023-09-15 17:54 ` Joseph Turner via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-09-15 18:00 ` Dmitry Gutov
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