Package: emacs;
Reported by: Joseph Turner <joseph <at> breatheoutbreathe.in>
Date: Thu, 7 Sep 2023 07:56:02 UTC
Severity: normal
Found in version 29.0.92
Done: Stefan Monnier <monnier <at> iro.umontreal.ca>
Bug is archived. No further changes may be made.
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From: Joseph Turner <joseph <at> breatheoutbreathe.in> To: Stefan Monnier <monnier <at> iro.umontreal.ca> Cc: dmitry <at> gutov.dev, Eli Zaretskii <eliz <at> gnu.org>, mattias.engdegard <at> gmail.com, philipk <at> posteo.net, 65797 <at> debbugs.gnu.org Subject: bug#65797: `buffer-match-p` should not use `func-arity` Date: Mon, 16 Oct 2023 13:16:32 -0700
Stefan Monnier <monnier <at> iro.umontreal.ca> writes:
>> Sigh. I guess we can install this on emacs-29 and cross the
>> fingers...
>
> I'm not insisting on it.
> If you think it's risky, let's just have it on `master`.
>
> BTW, see below the actual patch, including changes to etc/NEWS, manual,
> as well as the addition of a runtime warning (without which I can't see
> how we'll ever be able to get rid of the ugly backward compatibility
> hack).
Minor nit: There's a typo in the NEWS file. "tho" should be "though".
> Stefan
>
> [2. text/x-diff; buffer-match.patch]
> diff --git a/doc/lispref/buffers.texi b/doc/lispref/buffers.texi
> index 86c47ae7310..a2d0f5687ba 100644
> --- a/doc/lispref/buffers.texi
> +++ b/doc/lispref/buffers.texi
> @@ -957,10 +957,10 @@ Buffer List
> infinite recursion.
> @end defvar
>
> -@defun buffer-match-p condition buffer-or-name &optional arg
> +@defun buffer-match-p condition buffer-or-name &rest args
> This function checks if a buffer designated by @code{buffer-or-name}
> -satisfies the specified @code{condition}. Optional third argument
> -@var{arg} is passed to the predicate function in @var{condition}. A
> +satisfies the specified @code{condition}. Optional arguments
> +@var{args} are passed to the predicate function in @var{condition}. A
> valid @var{condition} can be one of the following:
> @itemize @bullet{}
> @item
> @@ -969,23 +969,21 @@ Buffer List
> name.
> @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).
> +matches. It is called with
> +@var{buffer-or-name} as the first argument followed by @var{args}.
> @item
> A cons-cell @code{(@var{oper} . @var{expr})} where @var{oper} is one
> of
> @table @code
> @item (not @var{cond})
> Satisfied if @var{cond} doesn't satisfy @code{buffer-match-p} with
> -the same buffer and @code{arg}.
> +the same buffer and @code{args}.
> @item (or @var{conds}@dots{})
> Satisfied if @emph{any} condition in @var{conds} satisfies
> -@code{buffer-match-p}, with the same buffer and @code{arg}.
> +@code{buffer-match-p}, with the same buffer and @code{args}.
> @item (and @var{conds}@dots{})
> Satisfied if @emph{all} the conditions in @var{conds} satisfy
> -@code{buffer-match-p}, with the same buffer and @code{arg}.
> +@code{buffer-match-p}, with the same buffer and @code{args}.
> @item derived-mode
> Satisfied if the buffer's major mode derives from @var{expr}.
> @item major-mode
> @@ -998,14 +996,14 @@ Buffer List
> @end itemize
> @end defun
>
> -@defun match-buffers condition &optional buffer-list arg
> +@defun match-buffers condition &optional buffer-list &rest args
> This function returns a list of all buffers that satisfy the
> @code{condition}. If no buffers match, the function returns
> @code{nil}. The argument @var{condition} is as defined in
> @code{buffer-match-p} above. By default, all the buffers are
> considered, but this can be restricted via the optional argument
> @code{buffer-list}, which should be a list of buffers to consider.
> -Optional third argument @var{arg} will be passed to @var{condition} in
> +Remaining arguments @var{args} will be passed to @var{condition} in
> the same way as @code{buffer-match-p} does.
> @end defun
>
> diff --git a/etc/NEWS b/etc/NEWS
> index 3bd47a0112b..c74b4978afe 100644
> --- a/etc/NEWS
> +++ b/etc/NEWS
> @@ -945,6 +945,13 @@ the file listing's performance is still optimized.
>
> * Incompatible Lisp Changes in Emacs 30.1
>
> +** `buffer-match-p and `match-buffers` take `&rest args`
> +They used to take a single `&optional arg` and were documented to use
> +an unreliable hack to try and accommodate condition predicates that
> +don't accept this optional arg.
> +The new semantics makes no such affordances, tho the code still
> +supports it (with a warning) for backward compatibility.
> +
> ** 'post-gc-hook' runs after updating 'gcs-done' and 'gcs-elapsed'.
>
> ---
> diff --git a/lisp/subr.el b/lisp/subr.el
> index 58274987d71..0732319ccd0 100644
> --- a/lisp/subr.el
> +++ b/lisp/subr.el
> @@ -7277,13 +7277,15 @@ string-lines
> (setq start (length string)))))
> (nreverse lines))))
>
> -(defun buffer-match-p (condition buffer-or-name &optional arg)
> +(defvar buffer-match-p--past-warnings nil)
> +
> +(defun buffer-match-p (condition buffer-or-name &rest args)
> "Return non-nil if BUFFER-OR-NAME matches CONDITION.
> CONDITION is either:
> - the symbol t, to always match,
> - the symbol nil, which never matches,
> - a regular expression, to match a buffer name,
> -- a predicate function that takes BUFFER-OR-NAME and ARG as
> +- a predicate function that takes BUFFER-OR-NAME plus ARGS as
> arguments, and returns non-nil if the buffer matches,
> - a cons-cell, where the car describes how to interpret the cdr.
> The car can be one of the following:
> @@ -7308,9 +7310,18 @@ buffer-match-p
> ((pred stringp)
> (string-match-p condition (buffer-name buffer)))
> ((pred functionp)
> - (if (eq 1 (cdr (func-arity condition)))
> - (funcall condition buffer-or-name)
> - (funcall condition buffer-or-name arg)))
> + (if (cdr args)
> + ;; New in Emacs>29.1. no need for compatibility hack.
> + (apply condition buffer-or-name args)
> + (condition-case-unless-debug err
> + (apply condition buffer-or-name args)
> + (wrong-number-of-arguments
> + (unless (member condition
> + buffer-match-p--past-warnings)
> + (message "%s" (error-message-string err))
> + (push condition buffer-match-p--past-warnings))
> + (apply condition buffer-or-name
> + (if args nil '(nil)))))))
> (`(major-mode . ,mode)
> (eq
> (buffer-local-value 'major-mode buffer)
> @@ -7332,17 +7343,17 @@ buffer-match-p
> (throw 'match t)))))))
> (funcall match (list condition))))
>
> -(defun match-buffers (condition &optional buffers arg)
> +(defun match-buffers (condition &optional buffers &rest args)
> "Return a list of buffers that match CONDITION, or nil if none match.
> See `buffer-match-p' for various supported CONDITIONs.
> By default all buffers are checked, but the optional
> argument BUFFERS can restrict that: its value should be
> an explicit list of buffers to check.
> -Optional argument ARG is passed to `buffer-match-p', for
> +Optional arguments ARGS are passed to `buffer-match-p', for
> predicate conditions in CONDITION."
> (let (bufs)
> (dolist (buf (or buffers (buffer-list)))
> - (when (buffer-match-p condition (get-buffer buf) arg)
> + (when (apply #'buffer-match-p condition (get-buffer buf) args)
> (push buf bufs)))
> bufs))
>
> diff --git a/lisp/window.el b/lisp/window.el
> index 2f9b46ebb0a..12d3fb1dfe7 100644
> --- a/lisp/window.el
> +++ b/lisp/window.el
> @@ -7535,10 +7535,8 @@ display-buffer-alist
> arguments: a buffer to display and an alist of the same form as
> ALIST. See `display-buffer' for details.
>
> -`display-buffer' scans this alist until it either finds a
> -matching regular expression or the function specified by a
> -condition returns non-nil. In any of these cases, it adds the
> -associated action to the list of actions it will try."
> +`display-buffer' scans this alist until the CONDITION is satisfied
> +and adds the associated ACTION to the list of actions it will try."
> :type `(alist :key-type
> (choice :tag "Condition"
> regexp
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