Subject: Re: bug#37774: 27.0.50; new :extend attribute broke visuals of all themes and other packages

From: Eli Zaretskii <[email-masked]>
Date: Wed, 16 Oct 2019 21:50:06 +0300

> From: Andrey Orst <[email-masked]>
> Date: Wed, 16 Oct 2019 21:13:23 +0300
> Cc: Ergus <[email-masked]>, [email-masked]
> 
> (defface foo...)
> (when (>= emacs-major-version 27)
>   (set-face-attribute foo... :extend t))

Yes, that could work as well.

My pint is that making defface version-dependent is very easy.