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

[Gregory Heytings <gregory@heytings.org>]

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>
> I'd find it quite surprising, since an errant edit to any open file 
> would prevent the server from exiting after the last client stops. While 
> leaving the server running isn't the worst thing ever (indeed, that's 
> how it works now), I'd want the logic for when the server exits to be as 
> simple as possible, i.e. "when there are no more clients, exit" 
> (provided the user has confirmed as necessary). Having the server stick 
> around because I forgot to save one file would surprise me, mainly 
> because it would typically happen after, well, I forgot something.
>

I see.  We have different mental models, I guess.  From my viewpoint the 
Emacs server should stay there until it's not necessary, and I'd be 
surprised to be queried about what to do with buffers opened of processes 
started in a frame I already closed when I want to close another frame. 
But of course I do not object to have both behaviors.

>
> That's pretty much what I started with, actually. I've added more to 
> that as I find corner cases, and as I try to make my code work well 
> under different configurations so that it could merge into Emacs if 
> there's interest.
>

I attach a patch for that other behavior, it works fine AFAICS.

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From 71fddcb7d0d6a8eb92a54c7933da1381b1c406ec Mon Sep 17 00:00:00 2001
From: Gregory Heytings <gregory@heytings.org>
Date: Sun, 24 Oct 2021 21:30:24 +0000
Subject: [PATCH] Option to stop Emacs server when last client exits.

* lisp/server.el (server-stop-when-closing-last-frame): New custom
variable.
* lisp/files.el (save-buffers-kill-terminal): Use the new custom
variable.
* doc/emacs/misc.texi (Emacs Server): Document it.
---
 doc/emacs/misc.texi | 8 ++++++++
 lisp/files.el       | 5 ++++-
 lisp/server.el      | 9 +++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/doc/emacs/misc.texi b/doc/emacs/misc.texi
index 893e5f1843..d7ec1d6322 100644
--- a/doc/emacs/misc.texi
+++ b/doc/emacs/misc.texi
@@ -1768,6 +1768,14 @@ Emacs Server
   emacs --daemon=foo
 @end example
 
+@vindex server-stop-when-closing-last-frame
+  When the last client frame is closed, unsaved buffers and running
+processes are normally kept in the daemon for later user.  However, if
+you set @code{server-stop-when-closing-last-frame} is non-@code{nil} and
+the last client frame is closed, Emacs asks you whether each unsaved
+buffer must be saved and each unfinished process must be killed, and
+the daemon itself is killed.
+
 @findex server-stop-automatically
   If you want to automatically stop the Emacs server when it has no
 clients, no unsaved buffers and no running processes anymore, put the
diff --git a/lisp/files.el b/lisp/files.el
index 5a6a33721b..268c017de4 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -7742,7 +7742,10 @@ save-buffers-kill-terminal
 If emacsclient was started with a list of file names to edit, then
 only these files will be asked to be saved."
   (interactive "P")
-  (if (frame-parameter nil 'client)
+  (if (and (frame-parameter nil 'client)
+           (if server-stop-when-closing-last-frame
+               (cddr (frame-list))
+             t))
       (server-save-buffers-kill-terminal arg)
     (save-buffers-kill-emacs arg)))
 \f
diff --git a/lisp/server.el b/lisp/server.el
index 944f1a3dce..239ce3a0a2 100644
--- a/lisp/server.el
+++ b/lisp/server.el
@@ -272,6 +272,15 @@ server-client-instructions
   :version "28.1"
   :type 'boolean)
 
+(defcustom server-stop-when-closing-last-frame nil
+  "Whether to stop the server when closing the last frame.
+If non-nil, call `save-buffers-kill-emacs' when the last client frame is
+closed.
+If nil, the last client frame is not handled differently, and
+`server-save-buffers-kill-terminal' is called when it is closed."
+  :version "29.1"
+  :type 'boolean)
+
 ;; We do not use `temporary-file-directory' here, because emacsclient
 ;; does not read the init file.
 (defvar server-socket-dir
-- 
2.33.0