Force_true parameter in highlight clause does not retrieve the fields properly

[guilherme_maranhao]

Hi everyone,

I set the following _source and highlight clauses in my search body:

{
 "_source":
  [
      "field_1",
      "field_2"
  ],
 "highlight":{
       "order":"score",
       "fragment_size":70,
       "number_of_fragments":3,
       "type":"plain",
       "pre_tags":["\u003cspan class  \"highlight\"\u003e"],
       "post_tags":["\u003c/span\u003e"],
       "fields":{
                "field_1":{"force_source":true},
                "field_2":{"force_source":true},
                "field_3":{"force_source":true},
                "field_4":{"force_source":true},
      }
}

According to https://www.elastic.co/guide/en/elasticsearch/reference/5.2/search-request-highlighting.html#_force_highlighting_on_source, I understood that, setting :force_source = true in the field highlight, if it occurs a matching on that field, it would be retrieved in the _source clause.

However, this does not happen with my search. The returned _source clause was:

hits": 
[
     {
			"_index": "index_name",
			"_type": "type_name",
			"_id": "3288191",
			"_score": 1897.5596,
			"_source": {
				"field_1": "201700000030",
				"field_2": {
					"id": 3,
					"desc": "foo"
				}
			},
			"highlight": {
				"field_3": ["something <span class=\"highlight\">search term</span>"],
				"field_4": [": another <span class=\"highlight\">search term</span> <span class=\"highlight\">search term</span>", ": foo bar - <span class=\"highlight\">search term</span>]
			}

Did I miss something or the "force_source" in this feature has nothing to with the _source clause?
If that's the case, how can I achieve this solution: retrieving a field in the _source clause only if there is a matching highlight on it?

Thanks,

Guilherme