[BUG] Optional bool in query string always True when parameter not present

Describe the bug

When query parameter of type Optional[bool] is declared using Query class parameter value is not correctly mapped and instead of None it maps to instance of Schema which when type casted to bool returns True.

To Reproduce

Sample code:

class QueryParams(BaseModel):
	foo: Optional[bool] = None

async def query_params(foo: Optional[bool] = Query(None, description="Some parameter")):
	return QueryParams(foo=foo)

@api.get("/foo")
async def get(data: QueryParams = Depends(query_params)):
	# When '/foo' is called (without any parameters) the 'foo' parameter 
  # inside 'data' has value of 'True' instead of 'None'.
	return None

It however works fine if declared as just:

async def query_params(foo: Optional[bool] = None):
	return QueryParams(foo=foo)

Expected behavior Value should be assigned only if parameter is present in query string, None otherwise.

Environment:

• OS: macOS
• FastAPI Version: 0.35
• Python version: 3.7.3

[LKay]

I got it. I refactored my code so I now have two function, both returning instance of my parameters models class.

[tiangolo]

Thanks for the help @dmontagu ! 🙇‍♂️ 🚀

Thanks for reporting back and closing the issue @LKay 🎉