Websocket Route Not Working With Nested Router

[uberbrodt]

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Example Code

from fastapi import APIRouter, FastAPI
from fastapi import WebSocket


router = APIRouter(prefix="/foo")
nested_router = APIRouter()
router.include_router(nested_router)
app = FastAPI()


# WORKS

# python -m websockets ws://localhost:8000/test-ws
@app.websocket("/test-ws")
async def test_ws(ws: WebSocket):
    await ws.accept()
    await ws.send_text("Hello World!")
    await ws.close()


# WORKS

# python -m websockets ws://localhost:8000/foo/test-ws
@router.websocket("/test-ws")
async def foo_test_ws(ws: WebSocket):
    await ws.accept()
    await ws.send_text("Hello World!")
    await ws.close()


# FAILS - 403 FORBIDDEN

# python -m websockets ws://localhost:8000/foo/bar/test-ws
@nested_router.websocket("/bar/test-ws")
async def bar_test_ws(ws: WebSocket):
    await ws.accept()
    await ws.send_text("Hello World!")
    await ws.close()


app.include_router(router)

Description

When upgrading from FastaAPI 0.72.0 to 0.78.0, noticed that a websocket path I had defined on a router included by another router was no longer available (server returns 403, trace logs indicate normal closure, think this is the normal behaviour when a websocket tries to upgrade a non-existent route).

Looks like #2640 fixed the case for a websocket defined on a router, but seems like the nested router makes this appear again.

Operating System

macOS

Operating System Details

FastAPI Version

0.78.8

Python Version

3.10.1

Additional Context

It's kinda weird that it did work before, since #98 would indicate that it's been a long standing problem. 🤷

[uberbrodt]

Alright so I pulled down the code and it seems like I can fix it with ordering the path definitions and the include_router. If I restructure the code like this:

from fastapi import APIRouter, FastAPI
from fastapi import WebSocket

nested_router = APIRouter()

# NOW WORKS 
# python -m websockets ws://localhost:8000/foo/bar/test-ws
@nested_router.websocket("/bar/test-ws")
async def bar_test_ws(ws: WebSocket):
    await ws.accept()
    await ws.send_text("Hello World!")
    await ws.close()

router = APIRouter(prefix="/foo")

# WORKS
# python -m websockets ws://localhost:8000/foo/test-ws
@router.websocket("/test-ws")
async def foo_test_ws(ws: WebSocket):
    await ws.accept()
    await ws.send_text("Hello World!")
    await ws.close()

router.include_router(nested_router)
app = FastAPI()

# WORKS
# python -m websockets ws://localhost:8000/test-ws
@app.websocket("/test-ws")
async def test_ws(ws: WebSocket):
    await ws.accept()
    await ws.send_text("Hello World!")
    await ws.close()

app.include_router(router)

I can then hit the nested router:

cbrodt@cbrodt-safely-you[fastapi]$  python -m websockets ws://localhost:8000/foo/bar/test-ws
Connected to ws://localhost:8000/foo/bar/test-ws.
< Hello World!
Connection closed: 1000 (OK).

So it seems like when calling include_router, it will miss any path operations not yet defined. Not sure on the right approach for a fix, but in the meantime maybe add a warning to the docs?

[qzcloveswcy]

Hello, I recently tried how to initiate a request to websocket in the sub-application, but found that the websocket parameter cannot be received in the sub-route. How to solve it?