Quart `json_provider_class` makes no effect

Question

I am trying to modify my datetime object responses in Quart so that my frontend applications receive dates in ISO8601 format.

I expected the json_provider_class to do this job, but it's not working for me or maybe I am not doing it right.

Here's my code:

class JSONProvider(DefaultJSONProvider):

    @staticmethod
    def default(object_):
        if isinstance(object_, (datetime.date, datetime.datetime)):
            return object_.isoformat()
        if isinstance(object_, (Decimal, UUID)):
            return str(object_)
        if is_dataclass(object_):
            return asdict(object_)
        if hasattr(object_, "__html__"):
            return str(object_.__html__())

        raise TypeError(
            f"Object of type {type(object_).__name__} is not JSON serializable")

    @staticmethod
    def dict_to_object(dict_):
        return dict_

    def loads(self, object_, **kwargs):
        return super().loads(object_, object_hook=self.dict_to_object, **kwargs)


app = Quart('Asaph API')
app.json_provider_class = JSONProvider

Dates are still in RFC 2822 format and I can't figure out a way to make Quart controllers return dates in ISO8601 format

score 0 · Answer 1 · answered May 17 '23 at 20:48

The DefaultJSONProvider is not meant to be extended, rather the JSONProvider class is,

from json import JSONEncoder

from quart.json import JSONProvider

class AsaphJSONEncoder(JSONEncoder):
    def default(self, object_: Any) -> Any:
        if isinstance(object_, (datetime.date, datetime.datetime)):
            return object_.isoformat()
        if isinstance(object_, (Decimal, UUID)):
            return str(object_)
        if is_dataclass(object_):
            return asdict(object_)
        if hasattr(object_, "__html__"):
            return str(object_.__html__())

        raise TypeError(
            f"Object of type {type(object_).__name__} is not JSON serializable")

class AsaphJSONProvider(JSONProvider):
    def dumps(self, object_: Any, **kwargs: Any) -> str:
        kwargs["cls"] = AsaphJSONEncoder
        return json.dumps(object_, **kwargs)

    def loads(self, object_: str | bytes, **kwargs: Any) -> Any:
        return json.loads(object_, **kwargs)

app = Quart('Asaph API')
app.json_provider_class = AsaphJSONProvider

Quart `json_provider_class` makes no effect

1 Answers1