skip_duplicates ignores weight

[nurey]

Elasticsearch version (bin/elasticsearch --version): 6.5.1, Build: default/tar/8c58350/2018-11-16T02:22:42.182257Z, JVM: 11.0.1

Plugins installed:
ingest-geoip
ingest-user-agent

JVM version (java -version):
openjdk version "11.0.1" 2018-10-16
OpenJDK Runtime Environment 18.9 (build 11.0.1+13)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.1+13, mixed mode)

OS version (uname -a if on a Unix-like system):
Linux 1f3aa3980dfa 4.9.125-linuxkit #1 SMP Fri Sep 7 08:20:28 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Description of the problem including expected versus actual behavior:

Running a suggest query with skip_duplicates set to true ignores weight of documents.

Steps to reproduce:

Create mapping:

PUT /listing_address
{
  "mappings": {
    "listing": {
      "properties": {
        "suggest": {
          "type": "completion",
          "analyzer": "standard",
          "contexts": [
          	{
          		"name": "status_and_rental",
          		"type": "category"
          	}
          ]
        }
      }
    }
  }
}

Index some documents:

PUT /listing_address/listing/123123123
{
"suggest": {
    "contexts": {
        "status_and_rental": "U"
    },
    "input": [
        "502-30 Church St, Toronto, ON, M5E1S7",
        "30 Church St Toronto ON M5E1S7"
    ],
    "weight": 662
}
}

PUT /listing_address/listing/123123124
{
"suggest": {
    "contexts": {
        "status_and_rental": "UR"
    },
    "input": [
        "502-30 Church St, Toronto, ON, M5E1S7",
        "30 Church St Toronto ON M5E1S7"
    ],
    "weight": 710
}
}

PUT /listing_address/listing/123123125
{
"suggest": {
    "contexts": {
        "status_and_rental": "U"
    },
    "input": [
        "502-30 Church St, Toronto, ON, M5E1S7",
        "30 Church St Toronto ON M5E1S7"
    ],
    "weight": 1228
}
}

"status_and_rental" varies from document to document with possible values of "U" or "UR". Weight varies between 662 and 1228.

Here's my search query:

POST /listing_address/_search?pretty
{
  "suggest": {
	 "address-suggest": {
    	"prefix": "502-30 church",
		"completion": {
			"field": "suggest",
			"size": 99,
			"skip_duplicates": true,
			"contexts": {
				"status_and_rental": ["UR", "U"]
			}
		}
      }
  }
}

The query returns one document with the weight of 662. But there are other documents with higher weight. I would expect the document with the highest weight to be returned.

[elasticmachine]

Pinging @elastic/es-search