bug#51377: Automatically exit server when it has no remaining clients

[Jim Porter <jporterbugs@gmail.com>]

On 10/24/2021 8:15 AM, Gregory Heytings wrote:
> 
> As discussed in 
> https://lists.gnu.org/archive/html/emacs-devel/2021-10/msg01465.html , 
> an option to stop the Emacs server when it has no clients anymore (which 
> is similar to what some other apps do, for example browsers) would be 
> useful.
> 
> Patch attached.

I'm not sure I understand the patch; `save-buffers-kill-emacs' prompts 
the user to save buffers before killing Emacs, but how would that work 
in a daemon when there are no frames remaining?

I use a slightly-modified form of the following in my configuration, 
which I'm working on hooking up to a flag to remember if the daemon was 
started lazily:

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(defun save-buffers-kill-terminal (&optional arg)
   "Offer to save each buffer, then kill the current connection.
If the current frame has no client or is the last client of a daemon,
kill Emacs itself using `save-buffers-kill-emacs'.

With prefix ARG, silently save all file-visiting buffers, then kill.

If emacsclient was started with a list of filenames to edit, then
only these files will be asked to be saved."
   (interactive "P")
   ;; Only kill the terminal if the current frame is a client. However, if
   ;; Emacs was started as a daemon and this is the last client, kill Emacs
   ;; entirely.
   (if-let ((this-client (frame-parameter nil 'client))
            ((not (and (daemonp)
                       (equal server-clients (list this-client))))))
       (server-save-buffers-kill-terminal arg)
     (save-buffers-kill-emacs arg)))

(defun server-kill-emacs-query-function ()
   "Ask before exiting Emacs if it has live clients.
If Emacs was started as a daemon and the only live client is the
current frame's client, don't bother asking."
   (let ((ignored-client (and (daemonp) (frame-parameter nil 'client))))
     (or (not (seq-some (lambda (client)
                          (unless (eq ignored-client client)
                            (seq-some #'buffer-live-p
                                      (process-get client 'buffers))))
                        server-clients))
         (yes-or-no-p "This Emacs session has clients; exit anyway? "))))

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