[Zope] Committing transaction by hand

[Maciek Pasternacki]

I'm writing Zope product supposed to give shopping cart functionality.
Order can be specified and completed by anonymous user; user should be
prompted for password in latest possible moment, i.e. when throwing
order to the cart.  Order is remembered in session variable.  When
user decides that order is complete I call (from unrestricted code)
something like:

    self.Cart().ThrowIn(self.REQUEST)

Cart() returns instance of `current' shopping cart (one that user is
currently using); when there is no current cart, one is created; when
user isn't logged in, Unauthorized is raised.  Cart is not calling
object's own method but independent callable object acquired by
calling object.

Now when user isn't logged in, Cart() raises Unauthorized, user gets
asked for login and password, and boom!  We have no order data in
REQUEST.SESSION after authentication.  I read in one of recent posts
on this list that it's because exception aborts ZODB transaction, so
I tried to work around the problem by committing transaction before
calling Cart(), so now our fragment looks like this:


    get_transaction().commit()
    self.Cart().ThrowIn(self.REQUEST)

It seems to work for now but I'm not really sure if such messing with
something usually done automagically by Zope won't have some obscure
and nasty side effects.  Am I doing something dangerous now or is this
the Right Way to deal with my problem and if it's not then what is?

		--japh

-- 
__    Maciek Pasternacki <maciekp at japhy.fnord.org> [ http://japhy.fnord.org/ ]
`| _   |_\  / { Any road followed to its end leads precisely nowhere.  Climb
,|{-}|}| }\/ the mountain just a little to test it's a mountain. From the top
\/   |____/ of the mountain you cannot see the mountain. } ( F.Herbert )  -><-