bug#46325: 27.1; C-d in an rmail summary does not work on the first message

[Eli Zaretskii <eliz@gnu.org>]

> From: Francesco Potortì <pot@gnu.org>
> Date: Fri, 05 Feb 2021 13:00:17 +0100
> 
> C-u M-x rmail RET some-mbox-format-mail-file # load a file in rmail
> <   	      	  			     # go to the first message
> h   	      	  			     # create a directory
> C-d					     # delete the current message
> 
> Since this is the first message, C-d should delete it, display a message
> saying that there are no previous messages and stay on the deleted
> message.  Instead, it does (apparently) nothing and stays on the
> (undeleted) message.

Thanks.

Rmail summary commands never display a message about no next/previous
undeleted message, only Rmail commands do.

But the main problem -- that C-d doesn't delete the current message --
is indeed a bug, which was introduced while trying to optimize
deletion of many messages.  Does the patch below fix the bug with
deletion?

diff --git a/lisp/mail/rmailsum.el b/lisp/mail/rmailsum.el
index 7f99ecd..f53e6e7 100644
--- a/lisp/mail/rmailsum.el
+++ b/lisp/mail/rmailsum.el
@@ -930,10 +930,11 @@ rmail-summary-delete-forward
   (unless (numberp count) (setq count 1))
   (let (del-msg
         (backward (< count 0)))
-    (while (and (/= count 0)
-		;; Don't waste time if we are at the beginning
-		;; and trying to go backward.
-		(not (and backward (bobp))))
+    (while (/= count 0)
+      ;; Don't waste time counting down without doing anything if we
+      ;; are at the beginning and trying to go backward.
+      (if (and backward (bobp))
+          (setq count -1))
       (rmail-summary-goto-msg)
       (with-current-buffer rmail-buffer
 	(setq del-msg rmail-current-message)