* server.el (server-sentinel): Uncomment code to delete connection file.

  (server-start): Save the connection file in the server property list.
  Delete it only when we are reasonably convinced that it is not owned by
  a running server.
  (server-force-delete): New command to force-delete the connection file,
  and stop the server if it is running.
  (server-running-p): Return t also for local TCP servers when we find a
  process with a matching PID, and :other for undecided cases.

1 files changed, 67 insertions, 28 deletions

diff --git a/lisp/server.el b/lisp/server.el
index d488fb1f4ca..627805da66c 100644
--- a/lisp/server.el
+++ b/lisp/server.el
@@ -325,11 +325,12 @@ If CLIENT is non-nil, add a description of it to the logged message."
              (process-query-on-exit-flag proc))
     (set-process-query-on-exit-flag proc nil))
   ;; Delete the associated connection file, if applicable.
-  ;; This is actually problematic: the file may have been overwritten by
-  ;; another Emacs server in the mean time, so it's not ours any more.
-  ;; (and (process-contact proc :server)
-  ;;      (eq (process-status proc) 'closed)
-  ;;      (ignore-errors (delete-file (process-get proc :server-file))))
+  ;; Although there's no 100% guarantee that the file is owned by the
+  ;; running Emacs instance, server-start uses server-running-p to check
+  ;; for possible servers before doing anything, so it *should* be ours.
+  (and (process-contact proc :server)
+       (eq (process-status proc) 'closed)
+       (ignore-errors (delete-file (process-get proc :server-file))))
   (server-log (format "Status changed to %s: %s" (process-status proc) msg) proc)
   (server-delete-client proc))
 
@@ -458,34 +459,37 @@ job.  To use the server, set up the program `emacsclient' in the
 Emacs distribution as your standard \"editor\".
 
 Optional argument LEAVE-DEAD (interactively, a prefix arg) means just
-kill any existing server communications subprocess."
+kill any existing server communications subprocess.
+
+If a server is already running, the server is not started.
+To force-start a server, do \\[server-force-delete] and then
+\\[server-start]."
   (interactive "P")
   (when (or
          (not server-clients)
          (yes-or-no-p
           "The current server still has clients; delete them? "))
-    (when server-process
-      ;; kill it dead!
-      (ignore-errors (delete-process server-process)))
-    ;; Delete the socket files made by previous server invocations.
-    (when server-socket-dir
-      (condition-case ()
-          (delete-file (expand-file-name server-name server-socket-dir))
-        (error nil)))
-    ;; If this Emacs already had a server, clear out associated status.
-    (while server-clients
-      (server-delete-client (car server-clients)))
-    ;; Now any previous server is properly stopped.
-    (if leave-dead
-        (progn
-          (server-log (message "Server stopped"))
-          (setq server-process nil))
-      (let* ((server-dir (if server-use-tcp server-auth-dir server-socket-dir))
-             (server-file (expand-file-name server-name server-dir)))
+    (let* ((server-dir (if server-use-tcp server-auth-dir server-socket-dir))
+           (server-file (expand-file-name server-name server-dir)))
+      (when server-process
+        ;; kill it dead!
+        (ignore-errors (delete-process server-process)))
+      ;; Delete the socket files made by previous server invocations.
+      (if (not (eq t (server-running-p server-name)))
+          ;; Remove any leftover socket or authentication file
+          (ignore-errors (delete-file server-file))
+        (setq server-mode nil) ;; already set by the minor mode code
+        (error "Server %S is already running" server-name))
+      ;; If this Emacs already had a server, clear out associated status.
+      (while server-clients
+        (server-delete-client (car server-clients)))
+      ;; Now any previous server is properly stopped.
+      (if leave-dead
+          (progn
+            (server-log (message "Server stopped"))
+            (setq server-process nil))
         ;; Make sure there is a safe directory in which to place the socket.
         (server-ensure-safe-dir server-dir)
-        ;; Remove any leftover socket or authentication file.
-        (ignore-errors (delete-file server-file))
         (when server-process
           (server-log (message "Restarting server")))
         (letf (((default-file-modes) ?\700))
@@ -516,6 +520,7 @@ kill any existing server communications subprocess."
                                :service server-file
                                :plist '(:authenticated t)))))
           (unless server-process (error "Could not start server process"))
+          (process-put server-process :server-file server-file)
           (when server-use-tcp
             (let ((auth-key
                    (loop
@@ -533,14 +538,48 @@ kill any existing server communications subprocess."
                         " " (int-to-string (emacs-pid))
                         "\n" auth-key)))))))))
 
+;;;###autoload
+(defun server-force-delete (&optional name)
+  "Unconditionally delete connection file for server NAME.
+If server is running, it is first stopped.
+NAME defaults to `server-name'.  With argument, ask for NAME."
+  (interactive
+   (list (if current-prefix-arg
+             (read-string "Server name: " nil nil server-name))))
+  (when server-mode (with-temp-message nil (server-mode -1)))
+  (let ((file (expand-file-name (or name server-name)
+                                (if server-use-tcp
+                                    server-auth-dir
+                                  server-socket-dir))))
+    (condition-case nil
+        (progn
+          (delete-file file)
+          (message "Connection file %S deleted" file))
+      (file-error
+       (message "No connection file %S" file)))))
+
 (defun server-running-p (&optional name)
-  "Test whether server NAME is running."
+  "Test whether server NAME is running.
+
+Return values:
+  nil              the server is definitely not running.
+  t                the server seems to be running.
+  something else   we cannot determine whether it's running without using
+                   commands which may have to wait for a long time."
   (interactive
    (list (if current-prefix-arg
              (read-string "Server name: " nil nil server-name))))
   (unless name (setq name server-name))
   (condition-case nil
-      (progn
+      (if server-use-tcp
+          (with-temp-buffer
+            (insert-file-contents-literally (expand-file-name name server-auth-dir))
+            (or (and (looking-at "127\.0\.0\.1:[0-9]+ \\([0-9]+\\)")
+                     (assq 'comm
+                           (system-process-attributes
+                            (string-to-number (match-string 1))))
+                     t)
+                :other))
         (delete-process
          (make-network-process
           :name "server-client-test" :family 'local :server nil :noquery t