Subject: bug#58951: [PATCH] ; Fix handling of 'not' by 'buffer-match-p'

From: Philip Kaludercic <[email-masked]>
Date: Tue, 01 Nov 2022 19:36:12 +0000

Tags: patch

In preparing bug#58950 I noticed that the 'not' clause is confusing, and
is misused on the place I could find it being used in the core
(show-paren-predicate).  The current implementation would require a
negation to be written as

    (not . CONDITION)

while it is more natural to write

    (not CONDITION)

which is more in line with (and ...) and (or ...).

The issue appears to go back to `project--buffer-check', that takes a
list of conditions instead of a single one.  This means that the above
are equivalent. since (not CONDITION) will check each element in the
unary list in (not . (CONDITION)).

I believe this is preferable to fixing `show-paren-predicate', as this
is the kind of issue a lot of people could trip over.

This patch is based on the patch from bug#58950, but can be back-ported
to the previous implementations if there are any issues with that report.

In GNU Emacs 29.0.50 (build 3, x86_64-pc-linux-gnu, GTK+ Version
 3.24.30, cairo version 1.16.0) of 2022-10-31 built on heron
Repository revision: 462a66e79edcc34ecbeef7cc1604765adfdc038e
Repository branch: feature/package+vc
System Description: Guix System

Configured using:
 'configure --with-pgtk --with-imagemagick
 PKG_CONFIG_PATH=/gnu/store/ssg343s6ldqdwh30136pnawhbgd0cb6i-profile/lib/pkgconfig:/gnu/store/ssg343s6ldqdwh30136pnawhbgd0cb6i-profile/share/pkgconfig'

>From cb88a512eacb3ad73c22682c9c794cdc80445f43 Mon Sep 17 00:00:00 2001
From: Philip Kaludercic <[email-masked]>
Date: Tue, 1 Nov 2022 20:27:17 +0100
Subject: [PATCH] ; Fix handling of 'not' by 'buffer-match-p'

* lisp/subr.el (buffer-match-p): Look up the cadr instead of the cdr
for the negation in 'not'.
---
 lisp/subr.el | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lisp/subr.el b/lisp/subr.el
index b667339db9..0252e66686 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -7023,7 +7023,7 @@ string-lines
                `(provided-mode-derived-p
                  (buffer-local-value 'major-mode ,buffer-sym)
                  ',mode))
-              (`(not . ,cond)
+              (`(not ,cond)
                `(not ,(funcall translate cond)))
               (`(or . ,conds)
                `(or ,@(mapcar translate conds)))
@@ -7045,7 +7045,7 @@ string-lines
   * `major-mode': the buffer matches if the buffer's major mode
     is eq to the cons-cell's cdr.  Prefer using `derived-mode'
     instead when both can work.
-  * `not': the cdr is interpreted as a negation of a condition.
+  * `not': the cadr is interpreted as a negation of a condition.
   * `and': the cdr is a list of recursive conditions, that all have
     to be met.
   * `or': the cdr is a list of recursive condition, of which at
-- 
2.38.0