[BUG] Incorrect ReDoc resource URL when "app.mount" is used

Describe the bug

There is a bug when API is organized with different versions (FastAPI apps) which mounted via global app.mount.

ReDoc duplicates mount’s prefix. For example, http://127.0.0.1:8000/v1/v1/test.

It works well in default OpenAPI Docs.

Environment:

• OS: [e.g. Linux / Windows / macOS]
• FastAPI Version [e.g. 0.3.0], get it with: 0.40.0

Additional context

import fastapi
from fastapi import APIRouter

app = fastapi.FastAPI(docs_url=None, redoc_url=None)
router = APIRouter()


@router.get("/users/", tags=["users"])
async def read_users():
    return [{"username": "Foo"}, {"username": "Bar"}]

apiV1 = fastapi.FastAPI(openapi_prefix="/v1", version="1.0.0")
apiV1.include_router(router)
app.mount("/v1", apiV1)

Screenshot

[ivankravets]

@HacKanCuBa thank you so much for your research!

[HacKanCuBa]

Oh shit, I got it!

Gonna check it out in the code