bug#71761: 29.3; Emacs-Lisp menu display is incorrect during Edebug

[Eli Zaretskii]

> Cc: 71761@debbugs.gnu.org
> Date: Fri, 28 Jun 2024 19:10:05 +0100
> From:  Jeremy Bryant via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> tpeplt <tpeplt@gmail.com> writes:
> 
> > Emacs Maintainers,
> >
> >    When a function has been instrumented for debugging with
> > Edebug and the debugger has entered the function for
> > stepping, the menu item ‘Emacs-Lisp’ does not list the
> > correct entries (which should be the same entries as they
> > were before entering the debugger) in its drop-down menu.
> > Instead, the drop-down menu lists two entries ‘Emacs-Lisp’
> > and ‘Emacs-Lisp’.  These two entries, in turn, are sub-menus
> > whose contents are the correct menu items for ‘Emacs-Lisp’,
> > namely, ‘Indent Line’, ‘Indent Region’, and so on.
> >
> >    After exiting the debugger, the menu items for the
> > ‘Emacs-Lisp’ menu item are displayed correctly.
> >
> > Recipe for reproducing this menu-display error:
> >
> >    1. Start Emacs from a shell prompt with: $ emacs -Q
> >
> >    2. Create a new Emacs Lisp file with C-x C-f, say,
> >       new-file.el
> >
> >    3. Create a simple Emacs Lisp function:
> >
> >       (defun new-fun (name)
> >         (if name 'some-name nil))
> >
> >    4. Instrument the function with C-u M-C-x.
> >
> >    5. Check the menu listing for ‘Emacs-Lisp’ to confirm
> >       that it is correct.
> >
> >    6. Invoke the instrumented function to enter Edebug:
> >
> >       (new-fun t)
> >
> >    7. Check the menu listing for ‘Emacs-Lisp’ to see that it
> >       now lists (only) two identical ‘Emacs-Lisp’ entries,
> >       each of which is a sub-menu.  The sub-menus will list
> >       the correct entries for ‘Emacs-Lisp’.
> >
> >    8. In the debugger, type ‘c’ to continue to complete the
> >       debugging session.  Once it has exited, check the
> >       ‘Emacs-Lisp’ menu item to confirm that it now has the
> >       correct entries.  Each time that Edebug is entered,
> >       the ‘Emacs-Lisp’ menu’s entries are two incorrect
> >       sub-menus.
> >
> >    Please let me know if anything above is unclear or if you are unable
> > to reproduce this problem.
> 
> The following may help to narrow down the problem:
> 
> In Emacs 29.4:
> I am able to reproduce the bug in Emacs GUI
> But in Emacs TTY (emacs -nw), the problem seems absent, the menu bar
> appears correct.

That could be a bug in TTY menus, or maybe a side effect of how the
menu bar is displayed there.

AFAICT, the duplicate menu is the consequence of the fact that
edebug-mode has its keymap inherit from emacs-lisp-mode:

  (defvar-keymap edebug-mode-map
    :parent emacs-lisp-mode-map

So when Edebug is activated, it wants to display yet another "Emacs
Lisp" menu on the menu bar.

Stefan, do you see a way to avoid that?

Or maybe we should not consider this a bug at all?  After all, what's
the damage?