Re: gnus marks nonexistent articles

[Simon Josefsson <jas@extundo.com>]

prj@po.cwru.edu (Paul Jarc) writes:

> I think I've figured it out now.  When Gnus finds that an article does
> not exist, it marks it as read.  But nnmaildir doesn't store marks for
> nonexistent articles.  (Does nnimap?  nnml?)

Nnimap tries hard to not reset Gnus' marks but only update them with
correct information from the server.  So if Gnus thinks a non-existing
article has some set of marks, nnimap never changes it.  This is what
is slowing down group entry, btw..  relevant code from
nnimap-request-update-info-internal:

	(when (nnimap-mark-permanent-p 'read)
	  (let (seen unseen)
	    ;; read info could contain articles marked unread by other
	    ;; imap clients!  we correct this
	    (setq seen (gnus-uncompress-range (gnus-info-read info))
		  unseen (imap-search "UNSEEN UNDELETED")
		  seen (gnus-set-difference seen unseen)
		  ;; seen might lack articles marked as read by other
		  ;; imap clients! we correct this
		  seen (append seen (imap-search "SEEN"))
		  ;; remove dupes
		  seen (sort seen '<)
		  seen (gnus-compress-sequence seen t)
		  ;; we can't return '(1) since this isn't a "list of ranges",
		  ;; and we can't return '((1)) since g-list-of-unread-articles
		  ;; is buggy so we return '((1 . 1)).
		  seen (if (and (integerp (car seen))
				(null (cdr seen)))
			   (list (cons (car seen) (car seen)))
			 seen))
	    (gnus-info-set-read info seen)))

I guess similar code could be used in nnmaildir too.

> nnmaildir-request-update-info returns only the marks it knows about;
> it removes marks supplied by Gnus that weren't stored by nnmaildir.
> So after it's called, all the nonexistent articles seem to exist as
> unread, as far as Gnus is concerned.  Even if nnmaildir is the only
> backend currently affected by this problem, I think it makes sense to
> fix this in Gnus:  gnus-request-update-info could artificially add
> (1 . (1- min)) to the read range after getting marks from the backend.
> Thoughts?  Objections?  Other ideas?

If it is that simple to fix it, I'm for it.  OTOH it might be a good
property that backends should never update marks on
server-non-existing articles; it would allow Gnus to have local
articles using those article numbers.