bug#47458: Terrible UX upgrading Emacs in Guix

[Ludovic Courtès]

Hi Mark,

Mark H Weaver <mhw@netris.org> skribis:

> Eventually, I realized what the problem was:
>
> (1) My existing emacs session started failing because
>     ~/.guix-profile/share/emacs/27.1 had disappeared out from under it.
>
> (2) My newly launched emacs sessions were failing because my
>     EMACSLOADPATH variable was still set to its old value, pointing at
>     /home/mhw/.guix-profile/share/emacs/27.1/lisp, which no longer
>     existed.
>
> I'm not sure why I've never run into this problem before.  I'm also not
> sure what can be done to make this better, but if anyone has ideas, that
> would be good.  If a 7+ year Guix veteran developer gets bitten badly by
> this, I doubt that less experienced users will be impressed.

Ouch.  “It used to be” (speaking like a veteran :-)) that Emacs in Guix
would not use EMACSLOADPATH.  Then we switched to EMACSLOADPATH, which
had some advantages, but necessarily has this drawback.

IIUC, <https://issues.guix.gnu.org/45359> is about possibly
backtracking.  Maxim, what’s the status of this one?

Thanks,
Ludo’.