bug#57652: 29.0.50; Warning setting attribute of face ‘term’

[David Ponce <da_vid@orange.fr>]

On 08/09/2022 10:42, Eli Zaretskii wrote:
>> Cc: 57652@debbugs.gnu.org, gregory@heytings.org
>> Date: Thu, 8 Sep 2022 10:22:31 +0200
>> From: David Ponce <da_vid@orange.fr>
>>
>>      "Apart from the values given below, each face attribute can have the
>> value ‘unspecified’.  This special value means that the face doesn’t
>> specify that attribute directly.  An ‘unspecified’ attribute tells Emacs
>> to refer instead to a parent face (see the description ‘:inherit’
>> attribute below); or, failing that, to an underlying face (*note
>> Displaying Faces::).  (However, ‘unspecified’ is not a valid value in
>> ‘defface’.)"
>>
>> So it seems that unspecified is not allowed in defface.
> 
> Where does it say that unspecified is not allowed?  (And this doc
> string is from set-face-attribute, not from defface.)

I mentioned what is currently in the Emacs Lisp reference manual 
(lisp.info): (elisp)Top > Display > Faces > Face Attributes

>> So, how to specify a missing attribute excepted by using nil in the
>> defface used in term.el?
> 
> If you don't have anything to say about an attribute, just don't
> mention it in defface.  That's what unspecified means, as the doc
> string says.  So I'm unsure why you would need "to specify a missing
> attribute".

It is not me, it is how it is currently implemented in term.el:

(defcustom term-default-fg-color nil
   "If non-nil, default color for foreground in Term mode."
   :group 'term
   :type '(choice (const nil) (string :tag "color")))
(make-obsolete-variable 'term-default-fg-color "use the face `term' 
instead."
                         "24.3")

(defcustom term-default-bg-color nil
   "If non-nil, default color for foreground in Term mode."
   :group 'term
   :type '(choice (const nil) (string :tag "color")))
(make-obsolete-variable 'term-default-bg-color "use the face `term' 
instead."
                         "24.3")

(defface term
   `((t
      :foreground ,term-default-fg-color
      :background ,term-default-bg-color
      :inherit default))
   "Default face to use in Term mode."
   :group 'term)