from contextlib import AsyncExitStack

from starlette.types import ASGIApp, Receive, Scope, Send


# Used mainly to close files after the request is done, dependencies are closed
# in their own AsyncExitStack
class AsyncExitStackMiddleware:
    def __init__(
        self, app: ASGIApp, context_name: str = "fastapi_middleware_astack"
    ) -> None:
        self.app = app
        self.context_name = context_name

    # people might be monkey patching this function (although that's not supported)
    async_exit_stack: AsyncExitStack,
    embed_body_fields: bool,
) -> SolvedDependency:
    request_astack = request.scope.get("fastapi_inner_astack")
    assert isinstance(request_astack, AsyncExitStack), (
        "fastapi_inner_astack not found in request scope"
    )

            # Starts customization
            response_awaited = False
            async with AsyncExitStack() as request_stack:
                scope["fastapi_inner_astack"] = request_stack
                async with AsyncExitStack() as function_stack:
                    scope["fastapi_function_astack"] = function_stack
                    response = await f(request)

                # new contextvars context copy by using a new AnyIO task group.
                # This AsyncExitStack preserves the context for contextvars, not
                # strictly necessary for closing files but it was one of the original
                # intentions.
                # If the AsyncExitStack lived outside of the custom middlewares and
                # contextvars were set, for example in a dependency with 'yield'

* ♻️ Update internal type annotations and upgrade mypy. PR [#9658](https://github.com/tiangolo/fastapi/pull/9658) by [@tiangolo](https://github.com/tiangolo).
* ♻️ Simplify `AsyncExitStackMiddleware` as without Python 3.6 `AsyncExitStack` is always available. PR [#9657](https://github.com/tiangolo/fastapi/pull/9657) by [@tiangolo](https://github.com/tiangolo).

### Upgrades