Per the title.
Needs a test.
New patch adds a test. It's throwing NPE, which I don't see when running the code with my real client/server. Seems like Something in the test stack is putting a null for a Signature. Mind having a look?
I've fixed the NPE. If the JSON result doesn't contain columns, Avatica now makes up the definitions by inspecting the fields of the metadata class, e.g. MetaTable.class.
Your version of the patch (still) works for me!
Fixed in http://git-wip-us.apache.org/repos/asf/incubator-calcite/commit/4d2f647a.
Resolved in release 1.2.0-incubating (2015-04-16)