Function use in the IdP

[Rod Widdowson]

> We don't have the latter, because it's not possible. The message contexts
> aren't children of the PRC, they're stored in the PRC itself. Crosswalking
> that isn't possible as far as I can see.

Damn.  So basically if all I have is a MessageContext I cannot get the PRC.
That would kinda indicate that we could usefully have a ScriptedFunction
which takes a MessageContext.

I suppose could just generalize the ScriptedContext to take any BaseContext,
but that feels too much like a risk.  Mind you and OTOH, I'm not aware that
there are any blade guards in place - AFAICS if we have configured the
navigation using Spring then whatever we configure is what will end up as
the parameter to the ScriptedFunction class.  We might well be advised to
add an explicit test that the context is a PRC.   But again this will fail
quickly in test, 

Perhaps we only go into type safety checking mode if someone has used the
constructor with the Class parameter (as discussed yesterday)

R