Rails - Nov 2010 - Accessing (updating?) the proxy_scope chain for named_scope (Rails 2.3.x)

I have many named_scopes chained together in the normal way.   So far
so good.  However in a couple of cases where:

1.  The named scope is actually a correlated subquery and I need to
pass additional scope into it sometimes.

2.  Where the presence of a named scope in the chain should change the
behaviour of a named_scope later in the chain

Given:  Product.price.volume.average_discount

I''d like the named_scope :average_discount to be able to reach back in
the proxy chain to see if :price is part of the chain (its an example
only, not the actual use case ).  And potentially ''adjust'' it.
#scoped_methods isn''t it - that''s populated only when in
with_scope.

Question 1:  How can I access to the current proxy chain from within a
named_scope?

Question 2:  Can I modify the proxy_options (shudder I know) without
some serious monkey patching?

Yes, I realise I could add parameters to these lambdas, but its not
very DRY to be passing in the same parameter to several methods in the
chain either.  Note I can''t always predict in advance what the scope
chain will be - it can be derived based upon user input dynamically
(think of a basic reporting system where the user specifies the
attributes they want in a table).

Any ideas or alternatives?

--Kip

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