[BUG] Mounting StaticFiles with an APIRouter doesn't work

Describe the bug

Mounting StaticFiles with an APIRouter doesn’t work.

To Reproduce

from typing import Any
from fastapi import FastAPI, Request, APIRouter
from fastapi.staticfiles import StaticFiles
from fastapi.testclient import TestClient

router = APIRouter()

@router.get("/")
async def foo(request: Request) -> Any:
    # this raises starlette.routing.NoMatchFound
    return request.url_for("static", path="/bar")

app = FastAPI()

router.mount("/static", StaticFiles(directory="."), name="static")
# uncomment to fix
# app.mount("/static", StaticFiles(directory="."), name="static")

app.include_router(router)

client = TestClient(app)
client.get("/")

• Execute the script, raises NoMatchFound
• Uncomment line to mount with app instead
• Executes as expected

Expected behavior

I can use APIRouter() as if it was a FastAPI() as noted in the docs.

[septatrix]

The underlying problems seems to be that the route does not get applied to the application. The cause is a very restrictive check:

https://github.com/tiangolo/fastapi/blob/f0388915a8b1cd9f3ae2259bace234ac6249c51a/fastapi/routing.py#L713-L721

This should be expanded to work with routing.BaseRoute

[lazka]

If there is a specific need to include static files under a router, could you outline why that feature would be more useful then the basic mounting on the app?

I have different modules with different static things in my app and wanted to separate everything. So that changing the prefix also changes the static prefix. And so they can live in another package not in the same repo.

Could you also point out the specific docs that were confusing so they can be clarified?

It’s here https://fastapi.tiangolo.com/tutorial/bigger-applications/#path-operations-with-apirouter “All the same options are supported.”, but I now see that this only refers to path operations.

(btw the search in the docs is broken, it just says “Initializing search” forever)