websocket_route does not work like I expect it should

[jmgurney]

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Example

Here's a self-contained minimal, reproducible, example with my use case:

from fastapi import FastAPI
from fastapi.testclient import TestClient
from fastapi.websockets import WebSocket

app = FastAPI()


@app.websocket_route("/ws/{arg}/something")
async def websocket(arg, websocket: WebSocket):
    await websocket.accept()
    await websocket.send_json({"msg": "Hello WebSocket"})
    await websocket.close()


def test_websocket():
    client = TestClient(app)
    with client.websocket_connect("/ws/this/something") as websocket:
        data = websocket.receive_json()
        assert data == {"msg": "Hello WebSocket"}

test_websocket()

Description

I copied and slightly modfied the example from https://fastapi.tiangolo.com/advanced/testing-websockets/ .

The issue is that fastapi.routing.APIRouter inherits from starlette.routing.Router, and so websocket_route is inherited from there, and it does not do dependency injection which is quite confusing. The APIRouter should either remove that method, clearly document it or override it so that a consistent interface is provided.

I will commit to creating PR to resolve the issue once I have received advice on how the developers want to resolve this issue. [too much time has passed]

The solution you would like

Fix up the example to use websocket instead of websocket_route (for people using a version of FastAPI that does not yet have the fix). Add websocket_route as an alias for websocket so that starlette's version does not get used.

Describe alternatives you've considered

As documented, I am now using websocket instead of websocket_route, but the project could be improved by making the changes above.

Environment

• OS: macOSX
• FastAPI Version: 0.62.0
• Python version: 3.8.0

[krishnardt]

websocket_route doesn't take any body parameters. Websockets does.
This will resolve the issue:

@app.websocket("/ws/{x}/something")
async def websocket(websocket: WebSocket, x: str):
	await websocket.accept()
	await websocket.send_json({"msg": "Hello WebSocket"})
	await websocket.close()

[wallyhall]

The query parameters are passed through and accessible if you use the (lower level) Starlette websocket_route approach:

@app.websocket_route("/ws/{arg}/something")
async def websocket(arg, websocket: WebSocket):
    print(websocket.path_params["arg"])  # as documented here: https://www.starlette.io/websockets/#path-parameters

You just don't get them as function/method arguments like FastAPI abstracts for you.