Re: [ELPA] Add fontaine package?

[Eli Zaretskii]

> From: Protesilaos Stavrou <info@protesilaos.com>
> Cc: emacs-devel@gnu.org
> Date: Fri, 29 Apr 2022 10:23:52 +0300
> 
> It is possible to have a typeface that has a light weight and another
> that hasn't.  If the user defines two presets in fontaine-presets and
> tries to switch from the one with the light weight to the other without
> it, they will encounter the aforementioned behaviour of
> set-face-attribute.

Did you try using set-face-font instead?  Its FONT argument can be a
font-spec, so you should be able to say things like

  (set-face-font 'default (font-spec :family "Hack" :weight 'light))

and get what you want, I think.