The ruby driver assumes that a field list specified to #find includes key names that should be included in the projected output. It converts these fields to a hash of the form {:field1 => 1, :field2 => 1}

Changes needed:
1) In the case that the list includes

{"score" => {"$meta" => 'textScore'}}

the driver needs to allow it to pass through unchanged. Right now it incorrectly converts it to

{{"score" => {"$meta" => "textScore"}}=>1}

2) Similarly, for sort,

{"score" => {"$meta" => "textScore"}}

should be an acceptable sort value. Values are now limited to Mongo::Conversions::ASCENDING_CONVERSION and Mongo::Conversions::DESCENDING_CONVERSION