[QUESTION] Am I doing something wrong with my models? Getting a validation error on my response.

Description

I am getting a validation error on the response for my API calls that retrieve users, and I am not quite sure where to g in terms fixing it.

I am using pieces of the postgres full stack example.

Once I log into the api docs, I am able to make the request to retrieve user information, but the request does not complete. A validation exception is raised by pydantic for the response object.

I have included the error details below and I setup a repo that recreates what I am experiencing. I think I am just missing something simple. Thanks in advance for any assistance!

Example Repo: https://github.com/Rehket/API-Issue

Traceback

  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\uvicorn\protocols\http\h11_impl.py", line 375, in run_asgi
    result = await app(self.scope, self.receive, self.send)
  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\starlette\applications.py", line 133, in __call__
    await self.error_middleware(scope, receive, send)
  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\starlette\middleware\errors.py", line 177, in __call__
    raise exc from None
  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\starlette\middleware\errors.py", line 155, in __call__
    await self.app(scope, receive, _send)
  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\starlette\middleware\base.py", line 25, in __call__
    response = await self.dispatch_func(request, self.call_next)
  File "C:/Users/adama/Workspace/Python/TryFast/app/main.py", line 34, in db_session_middleware
    response = await call_next(request)
  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\starlette\middleware\base.py", line 45, in call_next
    task.result()
  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\starlette\middleware\base.py", line 38, in coro
    await self.app(scope, receive, send)
  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\starlette\middleware\cors.py", line 76, in __call__
    await self.app(scope, receive, send)
  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\starlette\exceptions.py", line 73, in __call__
    raise exc from None
  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\starlette\exceptions.py", line 62, in __call__
    await self.app(scope, receive, sender)
  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\starlette\routing.py", line 585, in __call__
    await route(scope, receive, send)
  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\starlette\routing.py", line 207, in __call__
    await self.app(scope, receive, send)
  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\starlette\routing.py", line 40, in app
    response = await func(request)
  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\fastapi\routing.py", line 122, in app
    skip_defaults=response_model_skip_defaults,
  File "C:\Users\adama\.virtualenvs\TryFast\lib\site-packages\fastapi\routing.py", line 54, in serialize_response
    raise ValidationError(errors)
pydantic.error_wrappers.ValidationError: 1 validation error
response
  value is not a valid dict (type=type_error.dict)

[dmontagu]

@Rehket I don’t think you should need to do that, but I’m not sure what is causing the issue. It might be a model config issue? (Maybe if you set orm_mode = True on the config it would help? I’m not sure.)

[dmontagu]

It looks like a problem converting the sqlalchemy model to a pydantic model. Could you just test manually converting it to the pydantic model first? So at the end, rather than returning user (which is actually of type DBUser in your code), create a new (pydantic) User from user and return that.

Whether it works or not, it will probably shed some light on the issue; we can try to figure out how to get it working as expected after that.