SPAM in spam group is processed into that exact same group

[Tassilo Horn <tassilo@member.fsf.org>]

Hi all,

I use 2 IMAP accounts and the spam processing is done on the server
side.  Now I want to setup gnus' spam processing to move false positives
and false negatives into training groups by (un)marking them with $.
That's what I've come up with:

--8<---------------cut here---------------start------------->8---
(spam-initialize)
(setq gnus-spam-newsgroup-contents
      ;; My spam groups all have spam or Junk in their name
      '(("\\.\\(spam\\|Junk\\)" gnus-group-spam-classification-spam))

      ;; Move SPAM in normal groups to spam training or spam group.
      gnus-spam-process-destinations
      '(("nnimap\\+Fastmail:"
	 "nnimap+Fastmail:INBOX.training.spam")
	("nnimap\\+Uni:"
	 "nnimap+Uni:Junk"))

      ;; Move ham in spam groups to inbox and training.ham.
      gnus-ham-process-destinations
      '(("nnimap\\+Fastmail:INBOX\\.Junk Mail"
	 "nnimap+Fastmail:INBOX"
	 "nnimap+Fastmail:INBOX.training.ham")))
--8<---------------cut here---------------end--------------->8---

I think the processing basically works fine except one really annoying
issue:  as soon as I leave some spam group like

  nnimap+Fastmail:INBOX.Junk Mail
  nnimap+Fastmail:INBOX.training.spam
  nnimap+Uni:Junk

which all contain only messages marked as spam ($), all messages in the
summary buffer are moved from that group into the exact same group.  And
unmarking a spam article before leaving doesn't process that into my
inbox and training.ham group, too, but does nothing instead.

My understanding was that in spam groups only the ham processor is
invoked whereas in ham and unclassified groups only the spam processor
does its job, but that seems to be false.  It looks to me that only the
spam processor is invoked in all groups.

To make things worse, the docs talk about several variables that don't
exist in my emacs/gnus, both the current heads of their bzr/git
repositories, e.g. `spam-move-spam-nonspam-groups-only',
`spam-process-ham-in-spam-groups', or
`spam-process-ham-in-nonham-groups'.

What am I doing wrong, or is it a bug?

Bye,
Tassilo