Eli Zaretskii <eliz@gnu.org> writes:

> On October 14, 2020 10:41:01 AM GMT+03:00, Andreas Schwab
> <schwab@linux-m68k.org> wrote:
>> On Okt 14 2020, Lars Ingebrigtsen wrote:
>>
>> > (define-widget 'group 'default
>> >   "A widget which groups other widgets inside."
>> >   :convert-widget 'widget-types-convert-widget
>> >   :copy 'widget-types-copy
>> >   :format ":\n%v"
>> >
>> > But I have no idea how to override that in the context of a face
>> > definition.  Anybody?
>>
>> diff --git a/lisp/cus-edit.el b/lisp/cus-edit.el
>> index 9c5d89f89f..4cdd7ac564 100644
>> --- a/lisp/cus-edit.el
>> +++ b/lisp/cus-edit.el
>> @@ -3205,6 +3205,7 @@ face attributes (as specified by a `default'
>> defface entry)."
>>    :convert-widget 'custom-face-edit-convert-widget
>>    :args (mapcar (lambda (att)
>>    (list 'group :inline t
>> + :format "%v"
>>   :sibling-args (widget-get (nth 1 att) :sibling-args)
>>   (list 'const :format "" :value (nth 0 att))
>>   (nth 1 att)))
>>
>
>
> See also bug#33566, which is what caused this issue.

Andreas patch looks correct to me.  The custom-face-edit widget used the
default :format "%v" for the group widget, and then the default :format
was changed, but custom-face-edit didn't get updated to override it back
to "%v".