Search `to_dict()` does not serialize `rescore_query`

[Andrii32]

Hi. It seems like to_dict() method of Search class does not serialize rescore_querycontent.

Example code:

search = Search(index=index_name)

positive_query = Q(
   "function_score",
   query=Q('term', tags='a'),
   script_score={"script": "_score * 1"}
)

negative_query = Q(
   "function_score",
   query=Q('term', tags='b'),
   script_score={"script": "_score * -100"}
)

search = search.query(positive_query)
search = search.extra(
   rescore={
       'window_size': 100,
       "query": {
           "rescore_query": negative_query
       }
   }
)
print(search.query().to_dict())

Result:

{
    "query": {
        "function_score": {
            "query": {
                "term": {
                    "tags": "a"
                }
            },
            "functions": [
                {
                    "script_score": {
                        "script": "_score * 1"
                    }
                }
            ]
        }
    },
    "rescore": {
        "window_size": 100,
        "query": {
            "rescore_query": FunctionScore(
                functions=[
                    ScriptScore(script="_score * -100")
                ],
                query=Term(tags="b")
            )
        }
    }
}

Expected result:

{
    "query": {
        "function_score": {
            "query": {
                "term": {
                    "tags": "a"
                }
            },
            "functions": [
                {
                    "script_score": {
                        "script": "_score * 1"
                    }
                }
            ]
        }
    },
    "rescore": {
        "window_size": 100,
        "query": {
            "rescore_query": {
                "function_score": {
                    "query": {
                        "term": {
                            "tags": "b"
                        }
                    },
                    "functions": [
                        {
                            "script_score": {
                                "script": "_score * -100"
                            }
                        }
                    ]
                }
            }
        }
    }
}

Despite that, search executes properly.

[kiawin]

If no one is working on it, I would like to try this out :)

[kiawin]

@Andrii32 From a quick look at elasticsearch_dsl/search.py, the following .extra() did not perform any kind of serialization (a.k.a to_dict() of this issue title), and that explains why it remains object.

    def extra(self, **kwargs):
        """
        Add extra keys to the request body. Mostly here for backwards
        compatibility.
        """
        s = self._clone()
        if 'from_' in kwargs:
            kwargs['from'] = kwargs.pop('from_')
        s._extra.update(kwargs)
        return s

A question, may I know what is possible to be put inside .extra(), so that I can see how we can handle the serialization. Alternatively, we can recurse dictionary sent into .extra() to identify Q object and serialize them.