gnus-warp-to-article, nndoc, and virtual groups?

[Dave Abrahams <dave@boostpro.com>]

I have a very handy little function called "gnus-goto-article" that will
bring up an article by message-id in an otherwise-empty group:

#+begin_src lisp
(defun gnus-goto-article (message-id)
  (with-temp-buffer
    (erase-buffer)
    ;; Insert dummy article
    (insert (format "From nobody Tue Sep 13 22:05:34 2011\n\n"))
    (gnus-group-read-ephemeral-group
     message-id
     `(nndoc ,message-id
             (nndoc-address ,(current-buffer))
             (nndoc-article-type mbox))
     :activate
     (cons (current-buffer) gnus-current-window-configuration)
     (not :request-only)
     '(-1) ; :select-articles
     (not :parameters)
     0     ; :number
     )
    (gnus-summary-refer-article message-id)
    ))
#+end_src

[This is obviously a bit of a hack, but getting this capability was
hard-won to say the least]

Anyway, my problem is that from here, `gnus-warp-to-article' doesn't work
because nndoc groups aren't considered virtual.

#+begin_src lisp
(defun gnus-warp-to-article ()
  "Warps from an article in a virtual group to the article in its
real group. Does nothing on a real group."
  (interactive)
  (when (gnus-virtual-group-p gnus-newsgroup-name)
    (let ((gnus-command-method
           (gnus-find-method-for-group gnus-newsgroup-name)))
      (or
       (when (gnus-check-backend-function
              'warp-to-article (car gnus-command-method))
         (funcall (gnus-get-function gnus-command-method 'warp-to-article)))
       (and (bound-and-true-p gnus-registry-enabled)
            (gnus-try-warping-via-registry))))))
#+end_src

Recently we accepted a patch to make nnir groups virtual.  But this
brings up some more fundamental questions:

* What is "virtual" actually supposed to mean?
* Should "nndoc" be considered virtual?
* Should gnus-warp-to-article really be restricting itself to virtual
  groups?
* Should I be doing something different in `gnus-goto-article' to build
  a group with my message in it?

Thanks.

-- 
Dave Abrahams
BoostPro Computing                  Software Development        Training
http://www.boostpro.com             Clang/LLVM/EDG Compilers  C++  Boost