bug#65734: 29.1.50; kill-whole-line and visibility of Org subtrees

[Sebastian Miele]

In an emacs -Q, create an Org buffer with the following contents:

<-----cut-here----->
* AB
** C
<-----cut-here----->

Fold the subtree under the heading AB, so that only a single line is
diplayed (ending in "...").  With point between A and B, hit
C-S-<backspace> (kill-whole-line).

Expected: The whole _visible_ line, i.e., the entire contents of the
buffer is erased.  Actual behavior: The line with heading C remains.

Contrast this with the same experiment, except that the point is at the
beginning of the line containing AB when hitting C-S-<backspace>.  Then
the expected behavior happens.  And according to the source of
kill-whole-line, the intended effect indeed is to kill a whole _visible_
line.

The following patch fixes the issue:

diff --git a/lisp/simple.el b/lisp/simple.el
index abd587245fe..44221f3fc24 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -6649,9 +6649,7 @@ kill-whole-line
                             (unless (bobp) (backward-char))
                             (point))))
        (t
-        (save-excursion
-          (kill-region (point) (progn (forward-visible-line 0) (point))))
-        (kill-region (point)
+         (kill-region (save-excursion (forward-visible-line 0) (point))
                      (progn (forward-visible-line arg) (point))))))
 
 (defun forward-visible-line (arg)

The reason for the issue probably is: Without the patch, the killing
happens in two stages.  The first kill-region kills from the beginning
of the line until after the A.  That kills the leading *.  That probably
somehow triggers Org visibility changes.  With the patch applied the
whole killing happens in one stage, probably without causing an
intermediate change of visibility.


In GNU Emacs 29.1.50 (build 3, x86_64-pc-linux-gnu, GTK+ Version
 3.24.38, cairo version 1.17.8) of 2023-09-04 built on huette
Repository revision: 5cbe96d17f67e58091de1653f409d87bcc2b3e99
Repository branch: emacs-29
Windowing system distributor 'The X.Org Foundation', version 11.0.12101008
System Description: Arch Linux

Configured using:
 'configure --with-x-toolkit=gtk --with-native-compilation
 --with-tree-sitter --with-json --with-mailutils --with-imagemagick'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ
IMAGEMAGICK JPEG JSON LCMS2 LIBOTF LIBSYSTEMD LIBXML2 M17N_FLT MODULES
NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3
THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER WEBP X11 XDBE XIM XINPUT2
XPM GTK3 ZLIB

Important settings:
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Major mode: Lisp Interaction

Minor modes in effect:
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Load-path shadows:
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Memory information:
((conses 16 66653 8786)
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