get task status of forcemerge(wait_for_completion=false) results in error when task completed

Start at ElasticsearchTasksClient.get and the TaskStatus builder, then compare the completed force-merge JSON in the report with the generated response model. Reproduce the wait_for_completion=false flow against Elasticsearch 8.5.0 and verify that the completed response deserializes successfully without a response.batches field.

Java API client version

8.5.2

Java version

1.8

Elasticsearch Version

8.5.0

Problem description

when submit a force merge request with wait_for_completion=false, i got a taskid. and I use task id to query task status

 logger.info("force merge taskId: {}", taskId);
boolean completed = false;
GetTasksResponse tasksResponse = null;
while (!completed) {
    tasksResponse = client.tasks().get(t -> t.taskId(taskId));
    completed = tasksResponse.completed();
    logger.info("force merge task not completed yet");
    try {
        Thread.sleep(2 * 60_000);
    } catch (InterruptedException e) {
        throw new RuntimeException(e);
    }
}

all seems good when task is still running. but when task finally completes, get task response throws exception

Error deserializing co.elastic.clients.elasticsearch.tasks.GetTasksResponse: co.elastic.clients.util.MissingRequiredPropertyException: Missing required property 'TaskStatus.batches' (JSON path: response) (line no=1, column no=449, offset=-1)
	at co.elastic.clients.json.JsonpMappingException.from0(JsonpMappingException.java:134)
	at co.elastic.clients.json.JsonpMappingException.from(JsonpMappingException.java:121)
	at co.elastic.clients.json.ObjectDeserializer.deserialize(ObjectDeserializer.java:218)
	at co.elastic.clients.json.ObjectDeserializer.deserialize(ObjectDeserializer.java:148)
	at co.elastic.clients.json.JsonpDeserializer.deserialize(JsonpDeserializer.java:76)
	at co.elastic.clients.json.ObjectBuilderDeserializer.deserialize(ObjectBuilderDeserializer.java:79)
	at co.elastic.clients.json.DelegatingDeserializer$SameType.deserialize(DelegatingDeserializer.java:43)
	at co.elastic.clients.transport.rest_client.RestClientTransport.decodeResponse(RestClientTransport.java:325)
	at co.elastic.clients.transport.rest_client.RestClientTransport.getHighLevelResponse(RestClientTransport.java:295)
	at co.elastic.clients.transport.rest_client.RestClientTransport.performRequest(RestClientTransport.java:148)
	at co.elastic.clients.elasticsearch.tasks.ElasticsearchTasksClient.get(ElasticsearchTasksClient.java:117)
	at co.elastic.clients.elasticsearch.tasks.ElasticsearchTasksClient.get(ElasticsearchTasksClient.java:133)

and the completed response json string should be something like this

{
  "completed": true,
  "task": {
    "node": "xD7kSXXeSXWMURif3cX16w",
    "id": 2180131,
    "type": "transport",
    "action": "indices:admin/forcemerge",
    "description": "Force-merge indices [xxx], maxSegments[1], onlyExpungeDeletes[false], flush[true]",
    "start_time_in_millis": 1671621375383,
    "running_time_in_nanos": 9551767091603,
    "cancellable": false,
    "headers": {}
  },
  "response": {
    "_shards": {
      "total": 6,
      "successful": 6,
      "failed": 0
    }
  }
}

no response.batches exists however batches is force required in TaskStatus of the client code

private TaskStatus(Builder builder) {
    this.batches = ApiTypeHelper.requireNonNull(builder.batches, this, "batches");
    ...
}

i think this a bug not related to https://github.com/elastic/elasticsearch-specification/issues/1767, so i opened this issue