Don't let an empty summary change current message.

	* mail/rmailsum.el (rmail-summary-rmail-update):
	Detect empty summary and don't change selected message.
	(rmail-summary-goto-msg): Likewise.

2 files changed, 78 insertions, 64 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index f18d856a4dc..268a716fd09 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,9 @@
+2013-05-05  Richard Stallman  <rms@gnu.org>
+
+        * mail/rmailsum.el (rmail-summary-rmail-update):
+        Detect empty summary and don't change selected message.
+        (rmail-summary-goto-msg): Likewise.
+
 2013-05-05  Alan Mackenzie  <acm@muc.de>
 
         * progmodes/cc-defs.el (c-version): Increment to 5.32.5.
diff --git a/lisp/mail/rmailsum.el b/lisp/mail/rmailsum.el
index 13cd7c3f05e..ccd76cd6ba3 100644
--- a/lisp/mail/rmailsum.el
+++ b/lisp/mail/rmailsum.el
@@ -490,8 +490,7 @@ message."
     ;; we "don't have" a summary.
     (setq rmail-summary-buffer nil)
     ;; I have not a clue what this clause is doing.  If you read this
-    ;; chunk of code and have a clue, then please email that clue to
-    ;; pmr@pajato.com
+    ;; chunk of code and have a clue, then please  write it here.
     (if rmail-enable-mime
         (with-current-buffer rmail-buffer
           (setq rmail-summary-buffer nil)))
@@ -1122,57 +1121,59 @@ Search, the `unseen' attribute is restored.")
           (forward-line -1))
       (beginning-of-line)
       (skip-chars-forward " ")
-      (let ((msg-num (string-to-number (buffer-substring
-                                        (point)
-                                        (progn (skip-chars-forward "0-9")
-                                               (point))))))
-        ;; Always leave `unseen' removed
-        ;; if we get out of isearch mode.
-        ;; Don't let a subsequent isearch restore that `unseen'.
-        (if (not isearch-mode)
-            (setq rmail-summary-put-back-unseen nil))
-
-        (or (eq rmail-current-message msg-num)
-            (let ((window (get-buffer-window rmail-buffer t))
-                  (owin (selected-window)))
-              (if isearch-mode
-                  (progn
-                    ;; If we first saw the previous message in this search,
-                    ;; and we have gone to a different message while searching,
-                    ;; put back `unseen' on the former one.
-                    (when rmail-summary-put-back-unseen
-                      (rmail-set-attribute rmail-unseen-attr-index t
-                                           rmail-current-message)
-                      (save-excursion
-                        (goto-char rmail-summary-put-back-unseen)
-                        (rmail-summary-mark-seen rmail-current-message t t)))
-                    ;; Arrange to do that later, for the new current message,
-                    ;; if it still has `unseen'.
-                    (setq rmail-summary-put-back-unseen
-                          (if (rmail-message-unseen-p msg-num)
-                              (point))))
-                (setq rmail-summary-put-back-unseen nil))
-              ;; Go to the desired message.
-              (setq rmail-current-message msg-num)
-              ;; Update the summary to show the message has been seen.
-              (rmail-summary-mark-seen msg-num t)
-              (if window
-                  ;; Using save-window-excursion would cause the new value
-                  ;; of point to get lost.
-                  (unwind-protect
-                      (progn
-                        (select-window window)
-                        (rmail-show-message msg-num t))
-                    (select-window owin))
-                (if (buffer-name rmail-buffer)
-                    (with-current-buffer rmail-buffer
-                      (rmail-show-message msg-num t))))
-              ;; In linum mode, the message buffer must be specially
-              ;; updated (Bug#4878).
-              (and (fboundp 'linum-update)
-                   (buffer-name rmail-buffer)
-                   (linum-update rmail-buffer))))
-        (rmail-summary-update-highlight nil)))))
+      ;; If the summary is empty, don't do anything.
+      (unless (eobp)
+        (let ((msg-num (string-to-number (buffer-substring
+                                          (point)
+                                          (progn (skip-chars-forward "0-9")
+                                                 (point))))))
+          ;; Always leave `unseen' removed
+          ;; if we get out of isearch mode.
+          ;; Don't let a subsequent isearch restore that `unseen'.
+          (if (not isearch-mode)
+              (setq rmail-summary-put-back-unseen nil))
+
+          (or (eq rmail-current-message msg-num)
+              (let ((window (get-buffer-window rmail-buffer t))
+                    (owin (selected-window)))
+                (if isearch-mode
+                    (progn
+                      ;; If we first saw the previous message in this search,
+                      ;; and we have gone to a different message while searching,
+                      ;; put back `unseen' on the former one.
+                      (when rmail-summary-put-back-unseen
+                        (rmail-set-attribute rmail-unseen-attr-index t
+                                             rmail-current-message)
+                        (save-excursion
+                          (goto-char rmail-summary-put-back-unseen)
+                          (rmail-summary-mark-seen rmail-current-message t t)))
+                      ;; Arrange to do that later, for the new current message,
+                      ;; if it still has `unseen'.
+                      (setq rmail-summary-put-back-unseen
+                            (if (rmail-message-unseen-p msg-num)
+                                (point))))
+                  (setq rmail-summary-put-back-unseen nil))
+                ;; Go to the desired message.
+                (setq rmail-current-message msg-num)
+                ;; Update the summary to show the message has been seen.
+                (rmail-summary-mark-seen msg-num t)
+                (if window
+                    ;; Using save-window-excursion would cause the new value
+                    ;; of point to get lost.
+                    (unwind-protect
+                        (progn
+                          (select-window window)
+                          (rmail-show-message msg-num t))
+                      (select-window owin))
+                  (if (buffer-name rmail-buffer)
+                      (with-current-buffer rmail-buffer
+                        (rmail-show-message msg-num t))))
+                ;; In linum mode, the message buffer must be specially
+                ;; updated (Bug#4878).
+                (and (fboundp 'linum-update)
+                     (buffer-name rmail-buffer)
+                     (linum-update rmail-buffer))))
+          (rmail-summary-update-highlight nil))))))
 
 (defun rmail-summary-save-buffer ()
   "Save the buffer associated with this RMAIL summary."
@@ -1208,6 +1209,10 @@ Returns non-nil if message N was found."
                   (buffer-substring (point)
                                     (min (point-max) (+ 6 (point))))))
          (total (with-current-buffer buf rmail-total-messages)))
+    ;; CURMSG should be nil when there's no current summary message
+    ;; (for instance, if the summary is empty).
+    (if (= curmsg 0)
+        (setq curmsg nil))
     ;; If message number N was specified, find that message's line
     ;; or set message-not-found.
     ;; If N wasn't specified or that message can't be found.
@@ -1228,17 +1233,20 @@ Returns non-nil if message N was found."
                  (setq n curmsg)
                  (setq message-not-found t)
                  (goto-char cur))))
-    (rmail-summary-mark-seen n)
-    (rmail-summary-update-highlight message-not-found)
-    (beginning-of-line)
-    (unless skip-rmail
-      (let ((selwin (selected-window)))
-        (unwind-protect
-            (progn (rmail-pop-to-buffer buf)
-                   (rmail-show-message n))
-          (select-window selwin)
-          ;; The actions above can alter the current buffer.  Preserve it.
-          (set-buffer obuf))))
+    ;; N can be nil now, along with CURMSG,
+    ;; if the summary is empty.
+    (when n
+      (rmail-summary-mark-seen n)
+      (rmail-summary-update-highlight message-not-found)
+      (beginning-of-line)
+      (unless skip-rmail
+        (let ((selwin (selected-window)))
+          (unwind-protect
+              (progn (rmail-pop-to-buffer buf)
+                     (rmail-show-message n))
+            (select-window selwin)
+            ;; The actions above can alter the current buffer.  Preserve it.
+            (set-buffer obuf)))))
     (not message-not-found)))
 
 ;; Update the highlighted line in an rmail summary buffer.