deleting articles from search groups?

[Andrew Cohen <cohen@andy.bu.edu>]

I just added the ability to delete articles directly from an nnir buffer
(similar to moving them). nnir just passes the delete request up the
food chain to the original group holding the article.

But after doing this, I'm wondering whether or not this is a good
idea. Should we worry that someone might be surprised that an action on
the results of a search has the effect of deleting an article
permanently from its original group? But you might say the same thing
about moving articles. 

A secondary question (assuming that allowing deletes is the Right Thing)
is whether or not I've implemented it correctly:) Deleting articles is
done through the 'request-expire-articles function, so I've created one
for nnir. But this means that gnus-summary-expire-articles is called on
the nnir group upon summary-buffer exit. Stepping through this when
exiting an nnir group always shows the list of "expirable" articles as
nil and so no harm is done. Is this guaranteed? I'm guessing that since
nnir is an "ephemeral" group and doesn't really have marks that the list
of expirable articles (gnus-newsgroup-expirable) is always empty?

Andy