when use BaseHTTPMiddleware can't catch BackgroundTasks exceptions

[YuQibing]

When I use the BaseHTTPMiddleware middleware and add background tasks with BackgroundTasks, if the background task is missing a parameter, it does not raise an error. In fact, it should raise an exception.

---

from fastapi import FastAPI, Request, BackgroundTasks, HTTPException
from fastapi.responses import JSONResponse
from starlette.middleware.base import BaseHTTPMiddleware
from starlette.middleware.exceptions import ExceptionMiddleware
from starlette.middleware.cors import CORSMiddleware
from starlette.middleware.errors import ServerErrorMiddleware

async def generic_exception_handler(request: Request, exc: Exception):
    print("!!!exception")
    return JSONResponse(
        status_code=500,
        content={"message": "aaaa"},
    )


class LoggingMiddleware(BaseHTTPMiddleware):
    async def dispatch(self, request: Request, call_next):
        print(f"Request URL: {request.url}")
        response = await call_next(request)
        print(f"Response Status: {response.status_code}")
        return response

app = FastAPI()

app.add_middleware(LoggingMiddleware)


app.add_exception_handler(Exception, generic_exception_handler)


async def background_task(name: str):
    1/0

@app.get("/")
async def run_background_task(background_tasks: BackgroundTasks):
    background_tasks.add_task(background_task)
    return {"message": "Background task started"}

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[YuQibing]

async def coro() -> None:
                nonlocal app_exc

                async with send_stream:
                    try:
                        await self.app(scope, receive_or_disconnect, send_no_error)
                    except Exception as exc:
                        app_exc = exc

I find this exc not catch , why not raise exc here...