Re: Generality of defvar

[Christopher Dimech <dimech@gmx.com>]

> Sent: Thursday, July 28, 2022 at 9:37 PM
> From: thibaut.verron@gmail.com
> To: "Christopher Dimech" <dimech@gmx.com>, carlmarcos@tutanota.com, "Emanuel Berg" <incal@dataswamp.org>, "help-gnu-emacs" <help-gnu-emacs@gnu.org>
> Subject: Re: Generality of defvar
>
> On 28/07/2022 09:34, Christopher Dimech <dimech@gmx.com> wrote:
> > *Sent:* Thursday, July 28, 2022 at 7:06 PM
> > *From:* "Thibaut Verron" <thibaut.verron@gmail.com>
> > *To:* "Christopher Dimech" <dimech@gmx.com>
> > *Cc:* carlmarcos@tutanota.com, "Emanuel Berg" <incal@dataswamp.org>, 
> > "help-gnu-emacs" <help-gnu-emacs@gnu.org>
> > *Subject:* Re: Generality of defvar
> > Le jeu. 28 juil. 2022 à 08:42, Christopher Dimech <dimech@gmx.com 
> > <mailto:dimech@gmx.com>> a écrit :
> > 
> >     *Sent:* Thursday, July 28, 2022 at 4:39 AM
> >     *From:* "Thibaut Verron" <thibaut.verron@gmail.com
> >     <mailto:thibaut.verron@gmail.com>>
> >     *To:* "Christopher Dimech" <dimech@gmx.com <mailto:dimech@gmx.com>>
> >     *Cc:* carlmarcos@tutanota.com <mailto:carlmarcos@tutanota.com>,
> >     "Emanuel Berg" <incal@dataswamp.org <mailto:incal@dataswamp.org>>,
> >     "help-gnu-emacs" <help-gnu-emacs@gnu.org
> >     <mailto:help-gnu-emacs@gnu.org>>
> >     *Subject:* Re: Generality of defvar
> >     Le mer. 27 juil. 2022 à 18:29, Christopher Dimech <dimech@gmx.com
> >     <mailto:dimech@gmx.com>> a écrit :
> > 
> > 
> > 
> >          > Sent: Thursday, July 28, 2022 at 1:47 AM
> >          > From: "Thibaut Verron" <thibaut.verron@gmail.com
> >         <mailto:thibaut.verron@gmail.com>>
> >          > To: carlmarcos@tutanota.com <mailto:carlmarcos@tutanota.com>
> >          > Cc: "Emanuel Berg" <incal@dataswamp.org
> >         <mailto:incal@dataswamp.org>>, "help-gnu-emacs"
> >         <help-gnu-emacs@gnu.org <mailto:help-gnu-emacs@gnu.org>>
> >          > Subject: Re: Generality of defvar
> >          >
> >          > Le mer. 27 juil. 2022 à 15:24, <carlmarcos@tutanota.com
> >         <mailto:carlmarcos@tutanota.com>> a écrit :
> >          >
> >          > >
> >          > > Jul 27, 2022, 13:21 by thibaut.verron@gmail.com
> >         <mailto:thibaut.verron@gmail.com>:
> >          > >
> >          > > > Le mer. 27 juil. 2022 à 14:52, carlmarcos--- via Users
> >         list for the GNU
> >          > > Emacs text editor <> help-gnu-emacs@gnu.org
> >         <mailto:help-gnu-emacs@gnu.org>> > a écrit :
> >          > > >
> >          > > >>
> >          > > >>
> >          > > >>  Jul 27, 2022, 12:34 by >> incal@dataswamp.org
> >         <mailto:incal@dataswamp.org>>> :
> >          > > >>
> >          > > >>  > carlmarcos--- via Users list for the GNU Emacs text
> >         editor wrote:
> >          > > >>  >
> >          > > >>  >> (defun enable-error-diagnostics ()
> >          > > >>  >>  "Enable error diagnostics with backtrace buffer.
> >          > > >>  >> One can exit the debugger with the q command."
> >          > > >>  >>
> >          > > >>  >
> >          > > >>  > You can refer to keys in docstrings like this:
> >          > > >>  >
> >          > > >>  >  \\[forward-word]
> >          > > >>  >
> >          > > >>  > That way, it isn't hardcoded so if later
> >         changed/configured
> >          > > >>  > it'll still show the right key.
> >          > > >>  >
> >          > > >>  How can I figure out what key to use in the docstring
> >         for exiting the
> >          > > backtrace buffer?
> >          > > >>
> >          > > >
> >          > > > The function bound to 'q' is quit-window. But since this
> >         function
> >          > > doesn't have a global binding, you need to tell the
> >         docstring to use the
> >          > > appropriate keymap to look the binding up.
> >          > > >
> >          > > > Something like
> >          > > >
> >          > > >   "Enable error diagnostics with backtrace buffer.
> >          > > >
> >          > > > \\<backtrace-mode-map> (note: this is the part telling
> >         emacs where to
> >          > > look for the key)
> >          > > > One can exit the debugger with the `quit-window' command
> >         (bound to
> >          > > \\[quit-window])."
> >          > > >
> >          > > >
> >          > > Although quit-window is bound to q, the command
> >         \\[quit-window] just
> >          > > inserts
> >          > > M-x quit-window, rather than q.
> >          > >
> >          >
> >          > Yes, that's precisely because quit-window doesn't have a
> >         global binding.
> >          > You need to add \\<backtrace-mode-map> somewhere in the
> >         docstring to tell
> >          > emacs to show bindings for the backtrace buffers, rather than
> >         global
> >          > bindings.
> >          >
> >          > Best wishes,
> >          > Thibaut
> > 
> >         Sounds good advice, but the result could be
> > 
> >         Uses keymap ‘backtrace-mode-map’, which is not currently defined.
> > 
> >     My bad, it should have been debugger-mode-map.
> >     Not quite right yet.
> > 
> > I guess one should also put (require 'debug) at some point along with 
> > the function definition?
> > Seems more bother than it solves.  Cannot see how users would be able to 
> > figure all this complication
> > out.
> 
> For sure. But it's really a rare situation, and not one that is likely to hit first time users: one has to be writing a function with a docstring, and this docstring has to involve a key bound in a keymap defined in another file, and not loaded by default.
> 
> Even for users developing their own packages, usually the keymap will be defined in a file loaded at the same time as the function, completely hiding this subtlety.
> 
> Still, I would almost be tempted to consider this case a bug, and to expect that emacs should autoload debug.el to display the relevant information.
> 
> Thibaut

I concur Thibaut.  Do send a report as you suggest.