bug#70136: 30.0.50; compilation-mode [was: comint-mode] doesn't call hack-dir-local-variables-non-file-buffer

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Augusto Stoffel <arstoffel@gmail.com>,  70136@debbugs.gnu.org
> Date: Tue, 16 Apr 2024 17:49:08 -0400
> 
> > You are entitled to your opinions, but this is clearly a change in
> > behavior that will affect a lot of users (since compilation-mode and
> > its descendants are very popular and widely used).  Therefore, I don't
> > understand why you need concrete examples: the issue is crystal clear
> > just by thinking about it.
> 
> FWIW, back in 2010 (commit 8117868f0ce6) when we added support for
> dir-locals to non-file buffers, we did it without even a config var to
> turn it off.

That's not the same.  Also, we did quite a few things wrong regarding
backward compatibility over the years, and I don't want us to repeat
past mistakes.

> AFAICT the `dir-locals.el` format should already be sufficiently
> flexible to make it easy for users annoyed by the new behavior to
> recover the old behavior (without affecting older Emacsen).
> 
> I think we should make an effort to enable dir-locals in as many buffers
> as makes sense (but that can't be all buffers, because many buffers
> aren't really related to any particular place in the file system, in
> which case using the dir-locals setting of the directory that happens to
> be current when the buffer was created is too arbitrary).

Like I said: I'm okay with this change provided that it is opt-in.