ESQL: incomplete parsing support for query params

[astefan]

Description

For a query with params like "params": [{"x": 1}, {"y": 2}] running in a JVM with assertions disabled results in:

  "error": {
    "root_cause": [
      {
        "type": "x_content_parse_exception",
        "reason": "Failed to build [params] after last required field arrived"
      }
    ],
    "type": "x_content_parse_exception",
    "reason": "[3:19] [esql/query] failed to parse field [params]",
    "caused_by": {
      "type": "x_content_parse_exception",
      "reason": "Failed to build [params] after last required field arrived",
      "caused_by": {
        "type": "array_index_out_of_bounds_exception",
        "reason": "Index 1 out of bounds for length 0"
      }
    }
  }

but with assertions enabled:

[2023-09-07T13:03:21,434][ERROR][o.e.b.ElasticsearchUncaughtExceptionHandler] [runTask-0] fatal error in thread [Thread-2], exiting java.lang.AssertionError: [params] must configure at least one constructor argument. If it doesn't have any it should use ObjectParser instead of ConstructingObjectParser. This is a bug in the parser declaration.
┬╗      at org.elasticsearch.xcontent@8.11.0-SNAPSHOT/org.elasticsearch.xcontent.ConstructingObjectParser$Target.finish(ConstructingObjectParser.java:543)
┬╗      at org.elasticsearch.xcontent@8.11.0-SNAPSHOT/org.elasticsearch.xcontent.ConstructingObjectParser.parse(ConstructingObjectParser.java:166)
┬╗      at org.elasticsearch.xcontent@8.11.0-SNAPSHOT/org.elasticsearch.xcontent.ConstructingObjectParser.apply(ConstructingObjectParser.java:158)
┬╗      at org.elasticsearch.xpack.esql.action.EsqlQueryRequest.parseParams(EsqlQueryRequest.java:181)
┬╗      at org.elasticsearch.xcontent@8.11.0-SNAPSHOT/org.elasticsearch.xcontent.AbstractObjectParser.lambda$declareField$0(AbstractObjectParser.java:174)
┬╗      at org.elasticsearch.xcontent@8.11.0-SNAPSHOT/org.elasticsearch.xcontent.ObjectParser.lambda$declareField$10(ObjectParser.java:431)
┬╗      at org.elasticsearch.xcontent@8.11.0-SNAPSHOT/org.elasticsearch.xcontent.ObjectParser.parseValue(ObjectParser.java:609)
┬╗      at org.elasticsearch.xcontent@8.11.0-SNAPSHOT/org.elasticsearch.xcontent.ObjectParser.parseArray(ObjectParser.java:604)
┬╗      at org.elasticsearch.xcontent@8.11.0-SNAPSHOT/org.elasticsearch.xcontent.ObjectParser.parseSub(ObjectParser.java:643)
┬╗      at org.elasticsearch.xcontent@8.11.0-SNAPSHOT/org.elasticsearch.xcontent.ObjectParser.parse(ObjectParser.java:315)
┬╗      at org.elasticsearch.xcontent@8.11.0-SNAPSHOT/org.elasticsearch.xcontent.ObjectParser.parse(ObjectParser.java:259)
┬╗      at org.elasticsearch.xcontent@8.11.0-SNAPSHOT/org.elasticsearch.xcontent.ObjectParser.apply(ObjectParser.java:382)
┬╗      at org.elasticsearch.xpack.esql.action.EsqlQueryRequest.fromXContent(EsqlQueryRequest.java:144)
┬╗      at org.elasticsearch.xpack.esql.action.RestEsqlQueryAction.prepareRequest(RestEsqlQueryAction.java:45)

[elasticsearchmachine]

Pinging @elastic/es-ql (Team:QL)

[elasticsearchmachine]

Pinging @elastic/elasticsearch-esql (:Query Languages/ES|QL)