GNU bug report logs - #15718
24.3.50; `C-M-x' does not work, with `defcustom' inside `when'

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

From: Drew Adams <drew.adams <at> oracle.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.3.50; `C-M-x' does not work, with `defcustom' inside `when'
Date: Fri, 25 Oct 2013 08:44:44 -0700 (PDT)

emacs -Q

(when t
  (defcustom foo nil
   "..."
   :type boolean))

M-x set-variable foo t

Put point on foo in the defcustom sexp, and do `C-M-x'.  `foo' is echoed
in the echo area, giving you the impression that the defcustom was
reevaluated, reinitializing `foo'.

C-h v foo ;; => t, not nil.

Without the `when', i.e., with the `defcustom' at top level, the value
is nil, as a user would expect.



In GNU Emacs 24.3.50.1 (i686-pc-mingw32)
 of 2013-10-19 on LEG570
Bzr revision: 114715 rgm <at> gnu.org-20131019023520-s8mwtib7xcx9e05w
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --enable-checking 'CFLAGS=-O0 -g3' CPPFLAGS=-DGLYPH_DEBUG=1'

Message #8 received at 15718 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Drew Adams <drew.adams <at> oracle.com>
Cc: 15718 <at> debbugs.gnu.org
Subject: Re: bug#15718: 24.3.50; `C-M-x' does not work, with `defcustom'
 inside `when'
Date: Wed, 14 Aug 2019 19:57:02 -0700

Drew Adams <drew.adams <at> oracle.com> writes:

> emacs -Q
>
> (when t
>   (defcustom foo nil
>    "..."
>    :type boolean))
>
> M-x set-variable foo t
>
> Put point on foo in the defcustom sexp, and do `C-M-x'.  `foo' is echoed
> in the echo area, giving you the impression that the defcustom was
> reevaluated, reinitializing `foo'.
>
> C-h v foo ;; => t, not nil.
>
> Without the `when', i.e., with the `defcustom' at top level, the value
> is nil, as a user would expect.

I think this works as documented:

--
Evaluate the top-level form containing point, or after point.

If the current defun is actually a call to ‘defvar’ or ‘defcustom’,
evaluating it this way resets the variable using its initial value
expression (using the defcustom’s :set function if there is one), even
if the variable already has some other value.  (Normally ‘defvar’ and
‘defcustom’ do not alter the value if there already is one.)
--

So only if the def* is top-level does the magic DWIM value-setting thing
happen.

Closing.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #15 received at 15718 <at> debbugs.gnu.org (full text, mbox):

From: Drew Adams <drew.adams <at> oracle.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 15718 <at> debbugs.gnu.org
Subject: RE: bug#15718: 24.3.50; `C-M-x' does not work, with `defcustom'
 inside `when'
Date: Wed, 14 Aug 2019 21:41:37 -0700 (PDT)

> > emacs -Q
> >
> > (when t
> >   (defcustom foo nil
> >    "..."
> >    :type boolean))
> >
> > M-x set-variable foo t
> >
> > Put point on foo in the defcustom sexp, and do `C-M-x'.  `foo' is
> echoed
> > in the echo area, giving you the impression that the defcustom was
> > reevaluated, reinitializing `foo'.
> >
> > C-h v foo ;; => t, not nil.
> >
> > Without the `when', i.e., with the `defcustom' at top level, the
> value
> > is nil, as a user would expect.
> 
> I think this works as documented:
> 
> --
> Evaluate the top-level form containing point, or after point.
           ^^^^^^^^^^^^^^^^^^
> 
> If the current defun is actually a call to ‘defvar’ or ‘defcustom’,
> evaluating it this way resets the variable using its initial value
> expression (using the defcustom’s :set function if there is one), even
> if the variable already has some other value.  (Normally ‘defvar’ and
> ‘defcustom’ do not alter the value if there already is one.)
> --
> 
> So only if the def* is top-level does the magic DWIM value-setting
> thing happen.

Yes.  That's the problem.

This is an enhancement request - a request that it
instead work not just at the top level.

What's the reason why it should not "work" when
inside, say, `when'?  AFAIK, that feature just
hasn't been implemented yet.  Hence this request.
 
> Closing.

Unfortunate.

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