Configuring Shibboleth SP 2.6 to send attribute queries

[Misagh Moayyed]

I am working with an instance of Shibboleth SP 2.6, trying to have it issue attribute queries. This is a fairly vanilla SP with little to no mods. In trying to understand changes required to have the SP do so, I have the following: 

1. Ensure the IdP sends no attributes back to the SP. 
2. Ensure a nameid is provided in the response (transient?) 
3. Ensure the IdP metadata loaded by the SP has the appropriate AttributeAuthority elements, bindings, etc. 
4. The SP does by default seem to have an attribute resolver element of type query, which based on the wiki should do the trick. 

First, is the above list accurate? 

Assuming it is, what I see happening is the SP rejects the initial response with "AttributeStatement must have at least one attribute" which seems odd given #1. I suspect something else needs configuring in order to have the SP switch to using attribute queries. Suggestions on what I might have missed? 

--Misagh 
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