Using script_fields turns off _source retrieval

[Bargs]

Elasticsearch version: master (6861d35)
JVM version: 1.8.0_60
OS version: OSX 10.11.4

Description of the problem including expected versus actual behavior:

I recently discovered in Kibana master that creating a script field prevents other fields from loading on the Discover tab elastic/kibana#7699. The problem is that when script_fields is present in the query body, _source is no longer returned for each hit. Nothing has changed in the Kibana query as far as I can tell, so I think this is a change in behavior for ES.

Steps to reproduce:

1. Execute a query without script_fields, see that _source is returned by default.
2. Execute the same query with script_fields (any simple script should do, but it can't just be an empty object), see that _source is now missing

[clintongormley]

Yes, it has always been this way. The idea is that if you are specifying custom fields, then you don't want the full _source. Turn return the _source with script fields, just set ?_source=true

[Bargs]

Thanks @clintongormley, I see what changed in Kibana now. Sorry for the false alarm.