Trying to return entity but Validation error gets raised

[josushiman]

Hello 👋

I'm trying to return an entity which has two foreign keys associated to it. Any help or direction is appreciated! Thanks in advance.

class City(ormar.Model):
    class Meta(BaseMeta):
        tablename = "cities"
        constraints = [ormar.UniqueColumns("name"), ormar.UniqueColumns("iata")]

    id: int = ormar.Integer(primary_key=True)
    name: str = ormar.String(max_length=128)
    iata: str = ormar.String(max_length=128)
    timezone: Timezone = ormar.ForeignKey(Timezone, skip_reverse=True)
    capital: bool = ormar.Boolean(default=False)
    country: Country = ormar.ForeignKey(Country, skip_reverse=True)

I was able to create the city, as well as the associated timezone and country with no issue. However, when I try to get the city from the DB using a helper function, I get a validation error.

API call localhost:8000/city?iata=KBL and function:

@router.get("/", response_model=City)
async def get_city(iata: str) -> City:
    result = await db.get_by_kwarg(City, {
        "iata" : iata
    })

    return result

helper function

class DatabaseQuery():
    @classmethod
    async def get_by_kwarg(cls, entity: Model, kwarg: dict) -> Model:
        try:
            return await entity.objects.get(**kwarg)
        except NoMatch as e_404:
            logger.info(f"Could not find entity with kwarg: {kwarg}.", exc_info=e_404)
            raise HTTPException(status_code=404, detail=f"Could not find entity with kwarg: {kwarg}.")

error message

ERROR:    Exception in ASGI application
Traceback (most recent call last):
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/uvicorn/protocols/http/h11_impl.py", line 369, in run_asgi
    result = await app(self.scope, self.receive, self.send)
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/uvicorn/middleware/proxy_headers.py", line 59, in __call__
    return await self.app(scope, receive, send)
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/fastapi/applications.py", line 208, in __call__
    await super().__call__(scope, receive, send)
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/starlette/applications.py", line 112, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/starlette/middleware/errors.py", line 181, in __call__
    raise exc from None
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/starlette/middleware/errors.py", line 159, in __call__
    await self.app(scope, receive, _send)
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/starlette/middleware/trustedhost.py", line 34, in __call__
    await self.app(scope, receive, send)
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/starlette/middleware/cors.py", line 78, in __call__
    await self.app(scope, receive, send)
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/starlette/exceptions.py", line 82, in __call__
    raise exc from None
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/starlette/exceptions.py", line 71, in __call__
    await self.app(scope, receive, sender)
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/starlette/routing.py", line 580, in __call__
    await route.handle(scope, receive, send)
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/starlette/routing.py", line 241, in handle
    await self.app(scope, receive, send)
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/starlette/routing.py", line 52, in app
    response = await func(request)
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/fastapi/routing.py", line 227, in app
    response_data = await serialize_response(
  File "/home/josushiman/.local/share/virtualenvs/travl-info-api-cb_AeNoS/lib/python3.9/site-packages/fastapi/routing.py", line 130, in serialize_response
    raise ValidationError(errors, field.type_)
pydantic.error_wrappers.ValidationError: 6 validation errors for City
response -> name
  field required (type=value_error.missing)
response -> iso2
  field required (type=value_error.missing)
response -> iso3
  field required (type=value_error.missing)
response -> population
  field required (type=value_error.missing)
response -> demonym
  field required (type=value_error.missing)
response -> native_name
  field required (type=value_error.missing)

Model for both Country and Timezone

class Country(ormar.Model):
    class Meta(BaseMeta):
        tablename = "countries"
        constraints = [ormar.UniqueColumns("name"), ormar.UniqueColumns("iso2")]

    id: int = ormar.Integer(primary_key=True)
    name: str = ormar.String(max_length=128)
    iso2: str = ormar.String(max_length=128)
    iso3: str = ormar.String(max_length=128)
    population: int = ormar.Integer(maximum=9999999999)
    demonym: str = ormar.String(max_length=128)
    native_name: str = ormar.String(max_length=128)


class Timezone(ormar.Model):
    class Meta(BaseMeta):
        tablename = "timezones"

    id: int = ormar.Integer(primary_key=True)
    name: str = ormar.String(max_length=128)
    utc_offset: float = ormar.Float()

[josushiman]

I ended up finding what the cause was. For some reason, even though a City model is returned, having it set in the response model was causing it to throw the Internal Server Error i shared above.

The only change i had to make was this:

@router.get("/")
async def get_city(iata: str) -> City:
    result = await db.get_by_kwarg(City, {
        "iata" : iata
    })

    return result

[collerek]

Hi, if you removed the response model you skipped fastapi validation, that's why you don't have error anymore.
So that's a workaround not really the solution. You also removed the sample from the docs in swagger.

I will take a look at this. I suppose it has something to do with your helper. For sure you should be passing Type[Model] and return Model as you pass the class and return the city. From your code i don't know it, but model in that case should be ormar.Model. Fastapi is sensitive to annotations.

[josushiman]

Yup, that is correct, I also understand this is more of a workaround so you're right there as well. Here's the imports for the Helper, and all the models being passed to the helper are Ormar models.

from ormar import Model, NoMatch