Fix behavior of client frames when 'find-alternate-file' is used

* lisp/files.el (find-alternate-file-dont-kill-client): New var.
(find-alternate-file): Bind it to a special value when invoking
kill-buffer-hook.
* lisp/server.el (server-delete-client): If NOFRAME is
'dont-kill-client', don't kill the client and its terminals.
(server-buffer-done): Pass 'find-alternate-file-dont-kill-client'
to 'server-delete-client'.  (Bug#65277)

2 files changed, 20 insertions, 8 deletions

diff --git a/lisp/files.el b/lisp/files.el
index 68c0a10792d..3466a53d165 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -1998,6 +1998,8 @@ INHIBIT-BUFFER-HOOKS non-nil.
 Note: Be careful with let-binding this hook considering it is
 frequently used for cleanup.")
 
+(defvar find-alternate-file-dont-kill-client nil
+  "If non-nil, `server-buffer-done' should not delete the client.")
 (defun find-alternate-file (filename &optional wildcards)
   "Find file FILENAME, select its buffer, kill previous buffer.
 If the current buffer now contains an empty file that you just visited
@@ -2044,7 +2046,8 @@ killed."
     ;; save a modified buffer visiting a file.  Rather, `kill-buffer'
     ;; asks that itself.  Thus, there's no need to temporarily do
     ;; `(set-buffer-modified-p nil)' before running this hook.
-    (run-hooks 'kill-buffer-hook)
+    (let ((find-alternate-file-dont-kill-client 'dont-kill-client))
+      (run-hooks 'kill-buffer-hook))
     ;; Okay, now we can end-of-life the old buffer.
     (if (get-buffer " **lose**")
         (kill-buffer " **lose**"))
diff --git a/lisp/server.el b/lisp/server.el
index ba7e02d2555..10f15598221 100644
--- a/lisp/server.el
+++ b/lisp/server.el
@@ -330,6 +330,9 @@ ENV should be in the same format as `process-environment'."
 (defun server-delete-client (proc &optional noframe)
   "Delete PROC, including its buffers, terminals and frames.
 If NOFRAME is non-nil, let the frames live.
+If NOFRAME is the symbol \\='dont-kill-client, also don't
+delete PROC or its terminals, just kill its buffers: this is
+for when `find-alternate-file' calls this via `kill-buffer-hook'.
 Updates `server-clients'."
   (server-log (concat "server-delete-client" (if noframe " noframe")) proc)
   ;; Force a new lookup of client (prevents infinite recursion).
@@ -366,23 +369,28 @@ Updates `server-clients'."
             (set-frame-parameter frame 'client nil)
             (delete-frame frame))))
 
-      (setq server-clients (delq proc server-clients))
+      (or (eq noframe 'dont-kill-client)
+          (setq server-clients (delq proc server-clients)))
 
       ;; Delete the client's tty, except on Windows (both GUI and
       ;; console), where there's only one terminal and does not make
       ;; sense to delete it, or if we are explicitly told not.
       (unless (or (eq system-type 'windows-nt)
+                  ;; 'find-alternate-file' caused the last client
+                  ;; buffer to be killed, but we will reuse the client
+                  ;; for another buffer.
+                  (eq noframe 'dont-kill-client)
                   (process-get proc 'no-delete-terminal))
         (let ((terminal (process-get proc 'terminal)))
           ;; Only delete the terminal if it is non-nil.
           (when (and terminal (eq (terminal-live-p terminal) t))
             (delete-terminal terminal))))
 
-      ;; Delete the client's process.
-      (if (eq (process-status proc) 'open)
-          (delete-process proc))
-
-      (server-log "Deleted" proc))))
+      ;; Delete the client's process (or don't).
+      (unless (eq noframe 'dont-kill-client)
+        (if (eq (process-status proc) 'open)
+            (delete-process proc))
+        (server-log "Deleted" proc)))))
 
 (defvar server-log-time-function #'current-time-string
   "Function to generate timestamps for `server-buffer'.")
@@ -1590,7 +1598,8 @@ FOR-KILLING if non-nil indicates that we are called from `kill-buffer'."
                 ;; frames, which might change the current buffer.  We
                 ;; don't want that (bug#640).
                 (save-current-buffer
-                  (server-delete-client proc))
+                  (server-delete-client proc
+                                        find-alternate-file-dont-kill-client))
               (server-delete-client proc))))))
     (when (and (bufferp buffer) (buffer-name buffer))
       ;; We may or may not kill this buffer;