Subject: bug#54993: 28.1; Editing etc/NEWS on master with Emacs 28 signals an error

From: Jim Porter <[email-masked]>
Date: Mon, 18 Apr 2022 09:48:51 -0700

On 4/18/2022 1:41 AM, Lars Ingebrigtsen wrote:
> I've now fixed this regression, but I see there's (at least) one other:
> In Emacs 27, if the mode: had a mode that's not defined, it just says
> that it's ignored instead of trying to call it, which seems sensible, so
> I'll fix that regression, too.
> 
> But I can't get this to work in Emacs 27.2 -- Jim, are you sure that
> this worked at some point?

I just tried it in 27.2, and it works fine for me. If the "preferred" 
mode is defined, it uses that. Otherwise, it says "Ignoring unknown 
mode..." and uses the "basic" mode.

> mode: emacs-news; mode: outline-mode

It's probably failing for you because you need to do this in the 
opposite order (and remove the "-mode"):

   mode: outline; mode: emacs-news

It's a bit surprising at first, since as humans, we'd probably expect 
the "preferred" mode to be first, but the way this works is to activate 
outline-mode, and then (try to) activate emacs-news-mode. That's a 
little bit inefficient, but since this would mostly be used in cases 
where the "preferred" mode is derived from the "basic" mode, it's 
probably not too bad.