bug#68799: 30.0.50; emacs --fg-daemon fails silently if server-start fails

[Eli Zaretskii]

> From: Spencer Baugh <sbaugh@janestreet.com>
> Cc: 68799@debbugs.gnu.org,  monnier@iro.umontreal.ca,  jasonr@gnu.org
> Date: Tue, 13 Feb 2024 13:04:24 -0500
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Using DAEMON_RUNNING would mean any errors while starting the server
> > will fail to show the explicit error message about that.  That's a
> > regression in my book.  So I hope we can find a better solution.
> 
> Could you be more specific about what would regress in this situation?
> Preferably with a step by step of something that behaves worse.

I mean this error message:

  (let ((dn (daemonp)))
    (when dn
      (when (stringp dn) (setq server-name dn))
      (server-start)
      (if server-process
          (daemon-initialized)
        (if (stringp dn)
            (message
             "Unable to start daemon: Emacs server named %S already running"
             server-name)
          (message "Unable to start the daemon.\nAnother instance of Emacs is 
running the server, either as daemon or interactively.\nYou can use emacsclient 
to connect to that Emacs process."))
        (kill-emacs 1))))

> Currently the error message doesn't get shown at all, so I'm not clear
> what could be regressing.

We already established why the message doesn't show: because errors in
server-start are not caught.  I thought we also agreed that catching
the errors there and letting startup.el show the above error messages
is something that should be done.  I think your patch will prevent us
from doing that because the code which you suggest to patch with
DAEMON_RUNNING will kill Emacs before startup.el gets the chance to
show the error message, because daemon-initialized has not yet been
run by that time.