bug#21182: 25.0.50; gnus: every other unread message is marked as read on each nnimap group refresh

[Lars Ingebrigtsen <larsi@gnus.org>]

Nix <nix@esperi.org.uk> writes:

> It's hard to say -- I reverted the patch locally immediately. The
> problem is that whenever this goes wrong, 50% of my unread email gets
> marked as read, with no obvious way to reverse this. This is rather a
> high price to pay for replicating a bug :)
>
> I have some sacrificial folders I could give up to the cause -- I'll see
> if I can make things go wrong with them in the next day or so.

I just don't understand how the following patch could have this
effect...  

diff --git a/lisp/gnus/nnimap.el b/lisp/gnus/nnimap.el
index ced5561..8e81abc 100644
--- a/lisp/gnus/nnimap.el
+++ b/lisp/gnus/nnimap.el
@@ -166,14 +166,21 @@ nnimap-buffer
   (nnimap-find-process-buffer nntp-server-buffer))
 
 (defun nnimap-header-parameters ()
-  (format "(UID RFC822.SIZE BODYSTRUCTURE %s)"
-	  (format
+  (let (params)
+    (push "UID" params)
+    (push "RFC822.SIZE" params)
+    (when (nnimap-capability "X-GM-EXT-1")
+      (push "X-GM-LABELS" params))

So it only adds that to the params if the server supports it...

+    (push "BODYSTRUCTURE" params)
+    (push (format
 	   (if (nnimap-ver4-p)
 	       "BODY.PEEK[HEADER.FIELDS %s]"
 	     "RFC822.HEADER.LINES %s")
 	   (append '(Subject From Date Message-Id
 			     References In-Reply-To Xref)
-		   nnmail-extra-headers))))
+		   nnmail-extra-headers))
+	  params)
+    (format "%s" (nreverse params))))

So on non-Gmail servers the result should be identical...
 
-  (let (article lines size string)
+  (let (article lines size string labels)
     (block nil
       (while (not (eobp))
 	(while (not (looking-at "\\* [0-9]+ FETCH"))
@@ -232,6 +239,9 @@ nnimap-transform-headers
 				      t)
 		   (match-string 1)))
 	(beginning-of-line)
+	(when (search-forward "X-GM-LABELS" (line-end-position) t)
+	  (setq labels (ignore-errors (read (current-buffer)))))
+	(beginning-of-line)

Again, it should have no effect on non-Gmail...

 	(when lines
 	  (insert (format "Lines: %s\n" lines)))
+	(when labels
+	  (insert (format "X-GM-LABELS: %s\n" labels)))
 	;; Most servers have a blank line after the headers, but
 	;; Davmail doesn't.
 	(unless (re-search-forward "^\r$\\|^)\r?$" nil t)

And ditto.  So it's a mystery to me why that patch should affect
anything unless you're using Gmail..

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no