nnimap vs Zimbra; QRESYNC quirk; detect failure?

[Magnus Henoch <magnus.henoch@gmail.com>]

Hi all,

I just went back to using nnimap to connect to a Zimbra server.  The
server has been upgraded since the last time I did it, so I had the
usual symptoms: at Gnus startup, all the groups in the group buffer would
have an asterisk instead of the number of unread messages, hitting 'g'
would not change anything, but using M-g on every single group would
bring about the numbers.

I eventually worked out that I need to (setq nnimap-quirks nil), since
the Zimbra server is new enough.  Its version number is 7.2.3_GA_2872
(build 20130304145053), in case that helps anyone.  (see
http://comments.gmane.org/gmane.emacs.gnus.general/80154 for some
context)

I figured out the cause of the problem when I looked at the process
buffer and found this:

  2640 BAD parse error: wrong character; expected '(' but got ' '
  
  Process *nnimap* connection broken by remote peer

The problem I have with this is that nnimap could have told me about the
BAD response, or it could have told me about the connection closing, and
that would have sent me off in the right direction, but it did none of
these things.  I tried to do something about it, and started looking at
nnimap-wait-for-response which returns nil if the process is dead, and
also at nnimap-finish-retrieve-group-infos which does nothing if
nnimap-wait-for-response returns nil, but it seems like even if I signal
an error in those functions, it gets caught and ignored by some caller.

I think I'd want it to tell me that the connection was unexpectedly
closed, including the message after BAD (it's supposed to be human
readable, and even in the general case it's probably related to the
closed connection), and ask me if I'd want to reconnect.  Does that
sound reasonable?  Is it possible to accomplish that from within nnimap,
or do I need to hook this in somewhere else?

Regards,
Magnus