[BUG] Allow json/BaseModels in query parameters

Is your feature request related to a problem

I have to support getting a structured json string as parameter:

https://localhost:8080/test?moop={"name": "something %26 something else","description": "str" ,"price": 0.2,"tax": 0.2}&foo=bar

I would like to have a easy validation for those fields as well, as this could be automatic

The solution you would like

@routes.api_route('/test', methods=['GET', 'POST'], tags=['official', 'message', 'send'])
async def test(
    moop: Json[Item] = Query(..., description='Something something'),
    foo: str = Query(...),
):
    return {'woop': moop, 'lol': foo}
# end def

Initial version:

This was the initial thought, before I discovered the Json type.

@routes.api_route('/test', methods=['GET', 'POST'], tags=['official', 'message', 'send'])
async def test(
    moop: Item = Query(..., description='Something something'),
    foo: str = Query(...),
):
    return {'woop': moop, 'lol': foo}
# end def

Bug you face

AssertionError: Param: moop can only be a request body, using Body(...)

Describe alternatives you’ve considered

    moop: str

[w4tsn]

I’d like to ask again if this issue can be re-opened. I’m currently implementing a analytics backend which requires some rather complex query parameters in GET requests. I really enjoy writing models and schemas once and use them all out the code to just relax and watch fastapi to build the API documentation for me. It’s a real bummer that dirty hacks and dependency-work arounds (including me writing OpenAPI spec manually) are necessary to get this to work for every new function I implement.

[imankulov]

I think I found a good enough generic solution for parsing models in query strings.

Usage example:

class User(BaseModel):
    name: str

@app.get("/")
def root(user: User = json_param("user", User, description="User object")):
    return {"message": f"Hello, {user!r}"}

The code of json_param() is available in the gist snippet by the link.

https://gist.github.com/imankulov/cef71dd5a01f9a27caeb66f7bedaf241