GNU bug report logs - #80170
30.2; describe-mode incorrectly shows binding shadowed by minor mode

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Gal Lakovnik Gorenec <gal.lakovnik.gorenec <at> proton.me>
To: bug-gnu-emacs <at> gnu.org
Subject: 30.2; describe-mode incorrectly shows binding shadowed by minor mode
Date: Sat, 10 Jan 2026 00:22:47 +0000

Bug reproducible from a clean emacs:

Shell command:
emacs -Q --init-directory="$(mktemp -d)"

From within emacs:
package-install RET haskell-mode RET

eval the following use-package invocation:
NOTE: This is not a bug about tidal-mode

(use-package tidal
  :vc
  (:url "https://codeberg.org/uzu/tidal"))

Open an empty tidal file:
C-c C-f ~/test.tidal

Check describe-mode, describe-key and describe-bindings:
C-h m         -> (incorrectly) shows C-c C-c as bound to tidal-run-line
C-h k C-c C-c ->
  (correctly) shows C-c C-c as bound to haskell-process-cabal-build
C-h b         ->
  (correctly) shows C-c C-c as bound to haskell-process-cabal-build

tidal-mode is a fairly simple major-mode, derived from haskell-mode.
C-c C-c is part of its default keymap.
haskell-process-cabal-build belongs to the minor
haskell-interactive-mode,
enabled by the haskell-mode default hook.

-------------

In GNU Emacs 30.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.50,
cairo version 1.18.4)
System Description: Arch Linux

Configured using:
 'configure --with-pgtk --sysconfdir=/etc --prefix=/usr
 --libexecdir=/usr/lib --localstatedir=/var --disable-build-details
 --with-cairo --with-harfbuzz --with-libsystemd --with-modules
 --with-native-compilation=aot --with-tree-sitter 'CFLAGS=-march=x86-64
 -mtune=generic -O2 -pipe -fno-plt -fexceptions -Wp,-D_FORTIFY_SOURCE=3
 -Wformat -Werror=format-security -fstack-clash-protection
 -fcf-protection -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -g
 -ffile-prefix-map=/build/emacs/src=/usr/src/debug/emacs -flto=auto'
 'LDFLAGS=-Wl,-O1 -Wl,--sort-common -Wl,--as-needed -Wl,-z,relro
 -Wl,-z,now -Wl,-z,pack-relative-relocs -flto=auto'
 'CXXFLAGS=-march=x86-64 -mtune=generic -O2 -pipe -fno-plt -fexceptions
 -Wp,-D_FORTIFY_SOURCE=3 -Wformat -Werror=format-security
 -fstack-clash-protection -fcf-protection -fno-omit-frame-pointer
 -mno-omit-leaf-frame-pointer -Wp,-D_GLIBCXX_ASSERTIONS -g
 -ffile-prefix-map=/build/emacs/src=/usr/src/debug/emacs -flto=auto''

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

Important settings:
  value of $LANG: C.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Haskell Tidal

Minor modes in effect:
  interactive-haskell-mode: t
  haskell-indentation-mode: t
  tooltip-mode: t
  global-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
  minibuffer-regexp-mode: t
  line-number-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 shortdoc help-fns tidal pulse color
find-lisp scheme tidal-autoloads vc-hg vc-bzr vc-src vc-sccs vc-svn
vc-cvs vc-rcs log-view pcvs-util vc-git diff-mode track-changes
package-vc vc vc-dispatcher cl-extra use-package-core haskell-indent
haskell-doc advice comp-run comp-common haskell-c2hs ert ewoc debug
backtrace find-func quail help-mode inf-haskell haskell-decl-scan shell
pcomplete imenu haskell haskell-completions haskell-load
haskell-commands highlight-uses-mode haskell-modules haskell-sandbox
haskell-navigate-imports haskell-repl haskell-svg haskell-collapse
hideshow haskell-debug haskell-interactive-mode
haskell-presentation-mode haskell-compile haskell-process
haskell-session haskell-hoogle view haskell-mode haskell-cabal
haskell-utils haskell-font-lock haskell-indentation haskell-string
haskell-sort-imports haskell-lexeme rx haskell-align-imports
haskell-complete-module haskell-ghc-support noutline outline
flymake-proc flymake warnings thingatpt etags fileloop generator xref
project dabbrev haskell-customize compile comint ansi-osc ansi-color
ring info haskell-mode-autoloads easy-mmode loaddefs-gen lisp-mnt
radix-tree tar-mode arc-mode archive-mode cus-edit pp cus-start cus-load
wid-edit mm-archive message sendmail yank-media dired dired-loaddefs
rfc822 mml mml-sec epa derived gnus-util text-property-search time-date
mailabbrev gmm-utils mailheader mm-decode mm-bodies mm-encode mail-utils
gnutls network-stream url-cache url-http url-auth mail-parse rfc2231
rfc2047 rfc2045 mm-util ietf-drums mail-prsvr url-gw nsm puny epg
rfc6068 epg-config finder-inf package browse-url url url-proxy
url-privacy url-expand url-methods url-history url-cookie
generate-lisp-file url-domsuf url-util mailcap url-handlers url-parse
auth-source cl-seq eieio eieio-core cl-macs icons password-cache json
subr-x map byte-opt gv bytecomp byte-compile url-vars cl-loaddefs cl-lib
rmc iso-transl tooltip cconv eldoc paren electric uniquify ediff-hook
vc-hooks lisp-float-type elisp-mode mwheel term/pgtk-win pgtk-win
term/common-win touch-screen pgtk-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
dynamic-setting system-font-setting font-render-setting cairo gtk pgtk
lcms2 multi-tty move-toolbar make-network-process native-compile emacs)

Memory information:
((conses 16 343852 61074) (symbols 48 19172 6) (strings 32 81018 3736)
 (string-bytes 1 2626118) (vectors 16 34054)
 (vector-slots 8 452873 27821) (floats 8 240 316)
 (intervals 56 1773 151) (buffers 992 22))

-- 
Kind regards,
  Gal Lakovnik Gorenec

Message #8 received at 80170 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Gal Lakovnik Gorenec <gal.lakovnik.gorenec <at> proton.me>
Cc: 80170 <at> debbugs.gnu.org
Subject: Re: bug#80170: 30.2;
 describe-mode incorrectly shows binding shadowed by minor mode
Date: Sat, 10 Jan 2026 12:48:29 +0200

> Date: Sat, 10 Jan 2026 00:22:47 +0000
> From:  Gal Lakovnik Gorenec via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org>
> 
> 
> Bug reproducible from a clean emacs:
> 
> Shell command:
> emacs -Q --init-directory="$(mktemp -d)"
> 
> >From within emacs:
> package-install RET haskell-mode RET
> 
> eval the following use-package invocation:
> NOTE: This is not a bug about tidal-mode
> 
> (use-package tidal
>   :vc
>   (:url "https://codeberg.org/uzu/tidal"))
> 
> Open an empty tidal file:
> C-c C-f ~/test.tidal
> 
> Check describe-mode, describe-key and describe-bindings:
> C-h m         -> (incorrectly) shows C-c C-c as bound to tidal-run-line
> C-h k C-c C-c ->
>   (correctly) shows C-c C-c as bound to haskell-process-cabal-build
> C-h b         ->
>   (correctly) shows C-c C-c as bound to haskell-process-cabal-build
> 
> tidal-mode is a fairly simple major-mode, derived from haskell-mode.
> C-c C-c is part of its default keymap.
> haskell-process-cabal-build belongs to the minor
> haskell-interactive-mode,
> enabled by the haskell-mode default hook.

Thanks, but is it possible to show a reproduction recipe that requires
neither haskell nor tidal being installed?  If the problem is inherent
in the Emacs core, and this report is neither against haskell-mode nor
against tidal-modem there should be no problem with coming up with a
recipe that uses only the built-in features, right?

A recipe that doesn't depend on external packages is likely to be
handled faster and in a more efficient way.

TIA

Message #11 received at 80170 <at> debbugs.gnu.org (full text, mbox):

From: Gal Lakovnik Gorenec <gal.lakovnik.gorenec <at> proton.me>
To: 80170 <at> debbugs.gnu.org
Subject: Re: bug#80170: 30.2;
 describe-mode incorrectly shows binding shadowed by minor mode
Date: Sat, 10 Jan 2026 18:14:09 +0000

Hello Eli,

  my apologies. Pushing through my laziness would have saved me a bit of
  embarassment, and you a bit of time. In my defense, it was around 3 a.m. :)

  Evaluating the following code reproduces the issue (again, starting from a clean
  emacs session):

      (defvar shadow-bindings-mode-map
      (let ((map (make-sparse-keymap)))
        (define-key map (kbd "C-c C-c") 'shadow-message)
        map)
      "Keymap for shadow-bindings-mode")

      ;;;###autoload
      (define-minor-mode
        shadow-bindings-mode
        "A minor mode defining a binding that conflicts with a binding of a derived mode.
      Enabled by parent"
        :lighter " Shadowed"
        :keymap shadow-bindings-mode-map)

      ;;;###autoload
      (defun shadow-message ()
        (interactive)
        (message "This binding shadows a derived mode's binding"))

      (defvar parent-mode-hook '(shadow-bindings-mode))

      ;;;###autoload
      (define-derived-mode
        parent-mode
        prog-mode
        "Parent"
        "A parent mode that enables a minor mode via its startup hook.")

      (defun child-message ()
        (interactive)
        (message "Child-mode's binding calls this command."))

      (defvar child-mode-map
        (let ((map (make-sparse-keymap "Child Keymap")))
          (define-key map (kbd "C-c C-c") 'child-message)
          map)
        "Keymap for child-mode")

      ;;;###autoload
      (define-derived-mode
        child-mode
        parent-mode
        "Child"
        "A derived mode.")

      ;;;###autoload
      (add-to-list 'auto-mode-alist '("\\.xyz\\'" . child-mode))

  After evaluation, opening "test.xyz" exhibits the problem referred to
  in the original report, namely:
    C-c C-c runs 'shadow-message
    C-h m incorrectly lists "C-c C-c" as bound to 'child-message
    
  C-h k C-c C-c and C-h b both correctly show the binding.
  The issue persists regardless of whether the minor mode is enabled from
  the parent hook or manually.

  While writing this I noticed that the binding is correctly shown in
  the description of the minor mode. Is this the intended functionality?
  Is describe-mode supposed to show shadowed bindings without indicating
  said shadowing?

  Anyway, if this is NOT intended functionality -- I've been lurking in
  emacs-devel with the intention of starting to contribute and this
  (famous last words) doesn't seem too complicated. I'd be happy to
  submit a patch.

  P.S: Thank you and everyone else involved for your wonderful work.
  
-- 
Kind regards,
  Gal Lakovnik Gorenec

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