`.sourceExclude` and `.sourceInclude` are mutually exclusive

[tastyminerals]

Currently you can't use sourceExclude and sourceInclude together when constructing a SearchRequest. The latter will overwrite the former.

val request = search("test_index")
  .query(matchAllQuery)
  .sourceExclude(Seq("doc_id"))
  .sourceInclude(Seq("user_id"))

request.show

produces

POST /upload_read/_search
{"query":{"match_all":{}},"_source":{"includes":["user_id"]}}

In case the sourceInclude(Seq.empty), the request excludes will be similarly removed completely, producing "_source":true.

This could be the intended behavior, I am not sure because there is no documentation and no tests for using both of these functions. However, the classic elasticsearch library allows it and anyone who attempts a migration will end up having nasty silent bugs.

new SearchSourceBuilder().query(query).fetchSource(Array("doc_id"), Array("user_id"))

[Philippus]

I've created a fix for this in #3059.