bug#75387: 29.4; hideshow: hs-hide-level hides multiple top-level blocks as one

bug#75387: 29.4; hideshow: hs-hide-level hides multiple top-level blocks as one

[Christoph Groth]

Hello,

I noticed the following problem when using a homemade function that
allows me to cycle hideshow visibility in a way similar to org-mode.
The issue, however, is independent of any customization (it appears with
emacs -Q as well).

I can reproduce the issue with the following source file

https://gitlab.kwant-project.org/kwant/kwant/-/raw/0d679b3efecd145d13e3174c60d829a7c3cd4374/kwant/builder.py

I tried simplifying that file to isolate the issue, but did not arrive at
something more useful than the original.  To demonstrate the issue:

(1) Download the above file.
(2) Open it with emacs -Q builder.py.  Point is not moved.
(3) M-x hs-minor-mode RET
(4) M-x hs-hide-level RET

The result is that the buffer shows only two hidden blocks, with the
buffer ending in

@total_ordering
class SiteFamily(metaclass=abc.ABCMeta):...

This is incorrect, since there are many other classes and top-level
functions in the file.  Each should appear as a separate top-level
block.

If M-x hs-hide-all is run instead of step (4) the hiding works as
expected, many more top-level hidden blocks appear.  M-x hd-hide-level
also produces the expected effect if the second block created by (4) is
un-hidden in some way.  For example if the following two steps are added
to the above sequence:

(5) M-x hs-show-all RET
(6) M-x hs-hide-level RET

I would expect that hs-hide-level always produces the same result when
called with point at the same position in a buffer.

I hope that this somewhat obscure observation allows to fix some
inconsistency.

Thanks,
Christoph

---

In GNU Emacs 29.4 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.38,
 cairo version 1.16.0) of 2024-12-15, modified by Debian built on sbuild
Windowing system distributor 'The X.Org Foundation', version 11.0.12101007
System Description: Debian GNU/Linux 12 (bookworm)

Configured using:
 'configure --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/libexec
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-libsystemd --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/29.4/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/29.4/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils
 --with-native-compilation --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/libexec
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-libsystemd --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/29.4/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/29.4/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils
 --with-native-compilation --with-cairo --with-x=yes
 --with-x-toolkit=gtk3 --with-toolkit-scroll-bars 'CFLAGS=-g -O2
 -ffile-prefix-map=/build/reproducible-path/emacs-29.4+1=. -fstack-protector-strong
 -Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
 -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSELINUX 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:
  value of $LC_MESSAGES: en_US.UTF-8
  value of $LANG: en_DK.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068
epg-config gnus-util text-property-search time-date mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs
comp comp-cstr warnings icons subr-x rx cl-seq cl-macs gv cl-extra
help-mode bytecomp byte-compile cl-lib sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils rmc iso-transl tooltip cconv
eldoc paren electric uniquify ediff-hook vc-hooks lisp-float-type
elisp-mode mwheel term/x-win x-win term/common-win x-dnd tool-bar dnd
fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow
isearch easymenu timer select scroll-bar mouse jit-lock font-lock syntax
font-core term/tty-colors frame minibuffer nadvice seq simple cl-generic
indonesian philippine cham georgian utf-8-lang misc-lang vietnamese
tibetan thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek
romanian slovak czech european ethiopic indian cyrillic chinese
composite emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs
theme-loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads dbusbind inotify lcms2
dynamic-setting system-font-setting font-render-setting cairo
move-toolbar gtk x-toolkit xinput2 x multi-tty make-network-process
native-compile emacs)

Memory information:
((conses 16 77057 13062)
 (symbols 48 7444 0)
 (strings 32 19535 1545)
 (string-bytes 1 584589)
 (vectors 16 15338)
 (vector-slots 8 328476 18154)
 (floats 8 27 46)
 (intervals 56 275 0)
 (buffers 984 11))