bug#65411: 29.1; setopt of xref-after-jump-hook gives warning

[Howard Melman <hmelman@gmail.com>]

On Aug 20, 2023, at 11:36 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Howard Melman <hmelman@gmail.com>
>> Date: Sun, 20 Aug 2023 11:03:50 -0400
>> 
>> 
>> In Emacs 29.1 should I be able to do this:
>> 
>>    (setopt xref-after-jump-hook '(reposition-window xref-pulse-momentarily))
>> 
>> When I do in my init and then use xref-find-definition I get this warning:
>> 
>>    ⛔ Warning (emacs): Value `((reposition-window xref-pulse-momentarily))' for `xref-after-jump-hook' does not match type hook
> 
> xref-pulse-momentarily is not an autoloaded function, and xref.el is
> not preloaded.  You need to load xref.el, and then the above will
> work; it does for me.

Thanks very much. Indeed, doing this works fine for me:

(with-eval-after-load 'xref
  (setopt xref-after-jump-hook '(reposition-window xref-pulse-momentarily)))

Also I found doing (just) this works fine:

(setq xref-after-jump-hook '(reposition-window xref-pulse-momentarily))

So why does it fail using setopt?  AFAIU the xref-pulse-momentarily in the value
is just a symbol and I don't see the warning until I call xref-find-definition which
loads xref. And it works using setq without loading xref.

The warning shows double parentheses which I also don't understand how 
that happened (I see it does some widget conversion).  If there's some extra
restriction on using setopt to set hooks (which are user options), could it be 
explained in the manual or docstring?

Howard