GNU bug report logs - #16266
24.3; `load-theme' prevents immediate setting of themed variables

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

From: Alex Kost <alezost <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.3; `load-theme' prevents immediate setting of themed variables
Date: Fri, 27 Dec 2013 11:15:49 +0400

Specifying optional arguments (NOW, REQUEST, COMMENT) for ARGS of
`custom-theme-set-variables' doesn't take effect.

`load-theme' function has this piece:

	(let ((custom--inhibit-theme-enable t)  ;;; why this is here?
              (buffer-file-name fn))    ;For load-history.
	  (eval-buffer))

Because of that, a big piece of `custom-theme-set-variables' function is
never evaluated:

      (unless custom--inhibit-theme-enable      ;;; this var is always T
	;; Now set the variable.
	(let* ((now (nth 2 entry))
	       (requests (nth 3 entry))
	       (comment (nth 4 entry))
	       set)
          ...
          ))

I found a very similar letter to emacs.devel mailing list:
<http://lists.gnu.org/archive/html/emacs-devel/2012-07/msg00473.html>.

As far as I can see, this bug is in 24.3.50 as well.


In GNU Emacs 24.3.1 (i686-pc-linux-gnu, GTK+ Version 3.8.2)
 of 2013-08-07 on -mnt-storage-buildroots-staging-i686-eric

Message #8 received at 16266 <at> debbugs.gnu.org (full text, mbox):

From: Alex Kost <alezost <at> gmail.com>
To: 16266 <at> debbugs.gnu.org
Subject: Re: bug#16266: 24.3;
 `load-theme' prevents immediate setting of themed variables
Date: Fri, 27 Dec 2013 12:15:36 +0400

[Message part 1 (text/plain, inline)]

I've written a micro-theme to show the bug in action and to show why NOW
arg is vital.  The following can be tested with "emacs -Q".

1. Put "test-bug-theme.el" (attached) in `custom-theme-directory' (or
another dir from `custom-theme-load-path')

2. M-x load-theme RET test-bug RET

After that `test-var1' and `test-var2' are still void (because
`custom--inhibit-theme-enable' is set to T in `load-theme').

3. Evaluate these 2 expressions:

    (defcustom test-var1 "red" "some doc")
    (defvar test-var2 "red")

`test-var1' is "blue" now and `test-var2' is "red".  That's why NOW is
so necessary: a theme can set an undefined variable which will be
defined with `defvar' only using NOW arg.

[test-bug-theme.el (application/emacs-lisp, attachment)]

Message #11 received at 16266 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Alex Kost <alezost <at> gmail.com>
Cc: 16266 <at> debbugs.gnu.org
Subject: Re: bug#16266: 24.3; `load-theme' prevents immediate setting of
 themed variables
Date: Sun, 30 May 2021 07:20:54 +0200

Alex Kost <alezost <at> gmail.com> writes:

> 2. M-x load-theme RET test-bug RET
>
> After that `test-var1' and `test-var2' are still void (because
> `custom--inhibit-theme-enable' is set to T in `load-theme').
>
> 3. Evaluate these 2 expressions:
>
>     (defcustom test-var1 "red" "some doc")
>     (defvar test-var2 "red")
>
> `test-var1' is "blue" now and `test-var2' is "red".  That's why NOW is
> so necessary: a theme can set an undefined variable which will be
> defined with `defvar' only using NOW arg.

(I'm going through old bug reports that unfortunately got no response at
the time.)

I'm not sure I understand this test case.  The problem is that the
variables defined by the are "overwritten" when you load something that
is a defvar.  This does seem somewhat surprising, yes, but I think
that's how it's supposed to work?

The problem here is that test-var2 is a defvar instead of a defcustom -- if
that's the case, then themes don't work reliably, as you've found out.

So I think this is basically working as intended.  Does anybody have an
opinion here?

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

Message #16 received at 16266 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Alex Kost <alezost <at> gmail.com>
Cc: 16266 <at> debbugs.gnu.org
Subject: Re: bug#16266: 24.3; `load-theme' prevents immediate setting of
 themed variables
Date: Thu, 01 Jul 2021 13:41:54 +0200

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

> I'm not sure I understand this test case.  The problem is that the
> variables defined by the are "overwritten" when you load something that
> is a defvar.  This does seem somewhat surprising, yes, but I think
> that's how it's supposed to work?
>
> The problem here is that test-var2 is a defvar instead of a defcustom -- if
> that's the case, then themes don't work reliably, as you've found out.
>
> So I think this is basically working as intended.  Does anybody have an
> opinion here?

Nobody did, so I'm closing this bug report.  If this should receive more
work, please respond to this email and we'll reopen the bug report.

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

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