companies/_mget?_source_includes=countries.cities.name returns illegal_state_exception

[Marangal]

Elasticsearch Version

8.5.1

Installed Plugins

none

Java Version

elastic cloud docker

OS Version

elastic cloud docker

Problem Description

When executing .../companies/_mget?_source_includes=countries.cities.name
I get for certain data following error:
"error": {
"root_cause": [
{
"type": "illegal_state_exception",
"reason": "Failed to close the XContentBuilder"
}
],
"type": "illegal_state_exception",
"reason": "Failed to close the XContentBuilder",
"caused_by": {
"type": "i_o_exception",
"reason": "Unclosed object or array found"
}
}

Steps to Reproduce

1. prepare data:
   {
   "docs": [
   {
   "_index": "companies",
   "_id": "companyA",
   "_version": 1,
   "_seq_no": 10832,
   "_primary_term": 1,
   "found": true,
   "_source": {
   "countries": [
   {
   "cities": [
   {
   "name": "brussel"
   }
   ]
   },
   {
   "cities": []
   }
   ]
   }
   }
   ]
   }

2. Execute /companies/_mget?_source_includes=country.cities.name

When doing the same with following data it works:
{
"docs": [
{
"_index": "companies",
"_id": "companyB",
"_version": 1,
"_seq_no": 10832,
"_primary_term": 1,
"found": true,
"_source": {
"countries": [
{
"cities": [
{
"name": "brussel"
}
]
},
{
"cities": [
{
"name": "amsterdam"
}
]
}
]
}
}
]
}

This works too:

{
"docs": [
{
"_index": "companies",
"_id": "companyC",
"_version": 1,
"_seq_no": 10832,
"_primary_term": 1,
"found": true,
"_source": {
"countries": [
{
"cities": []
},
{
"cities": []
}
]
}
}
]
}

This works too:

{
"docs": [
{
"_index": "companies",
"_id": "companyD",
"_version": 1,
"_seq_no": 10832,
"_primary_term": 1,
"found": true,
"_source": {
"countries": [
{
"cities": [
{
"name": "brussel"
}
]
},
{
"cities": []
},
{
"cities": [
{
"name": "amsterdam"
}
]
}
]
}
}
]
}

Logs (if relevant)

Invalid NEST response built from a successful (200) low level call on POST: /articles/_mget?_source_includes=countries.cities.name

Audit trail of this API call:

• [1] HealthyResponse: Node: https://b5c19243ae1******248f9a54cfd97e.westeurope.azure.elastic-cloud.com/ Took: 00:00:00.0791874

Request:

{"ids":["companyA"]}

Response:

{
"docs": [
{
"_index": "companies",
"_type": "_doc",
"_id": "companyA",
"error": {
"root_cause": [
{
"type": "exception",
"reason": "Failed to get id [companyA] with includes/excludes set"
}
],
"type": "exception",
"reason": "Failed to get id [companyA] with includes/excludes set",
"caused_by": {
"type": "json_parse_exception",
"reason": "Unexpected problem: chain of filtered context broken\n at [Source: (org.elasticsearch.common.io.stream.ByteBufferStreamInput); line: 1, column: 2503]"
}
}
}
]
}

[DaveCTurner]

Looks like a duplicate of #92480, fixed in 8.6.1.