bug: CORS middleware not working with mounted applications

[byte-bot-app[bot]]

Reported by

peter in Discord: CORS middleware not working with mounted applications

Description

CORS pre-flight requests are passed to the mounted application, and not handled by the framework's CORS implementation.

MCVE

from http import HTTPStatus

import uvicorn
from litestar import Litestar, get, Response, asgi
from litestar.config.cors import CORSConfig

@get("/route")
async def route() -> Response[str]:
    return Response(content="Content", status_code=HTTPStatus.METHOD_NOT_ALLOWED)

cors_config = CORSConfig(allow_methods=["*"], allow_origins=["https://some-domain.com"])
app = Litestar(
    cors_config=cors_config,
    route_handlers=[
        asgi("/app", is_mount=True)(Litestar()),
        route,
    ]
)

if __name__ == "__main__":
    uvicorn.run("main:app", reload=True)

import httpx

for path in ["/app", "/route"]:
    response = httpx.options(
        f"http://127.0.0.1:8000{path}",
        headers={"origin": "https://some-domain.com"},
    )
    print(response.status_code)
    print(response.content)
    print(response.headers)

Logs

           /^\/^\
         _|__|  O|
\/     /~     \_/ \
 \____|__________/  \
        \_______      \
                `\     \                 \
                  |     |                  \
                 /      /                    \
                /     /                       \\
              /      /                         \ \
             /     /                            \  \
           /     /             _----_            \   \
          /     /           _-~      ~-_         |   |
         (      (        _-~    _--_    ~-_     _/   |
          \      ~-____-~    _-~    ~-_    ~-_-~    /
            ~-_           _-~          ~-_       _-~
               ~--______-~                ~-___-~

Litestar Version

2.8.2

---

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[github-actions[bot]]

This issue has been closed in #3401. The change will be included in the upcoming patch release.