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from __future__ import annotations
import typing
import anyio
from starlette._utils import collapse_excgroups
from starlette.requests import ClientDisconnect, Request
from starlette.responses import AsyncContentStream, Response
from starlette.types import ASGIApp, Message, Receive, Scope, Send
RequestResponseEndpoint = typing.Callable[[Request], typing.Awaitable[Response]]
DispatchFunction = typing.Callable[[Request, RequestResponseEndpoint], typing.Awaitable[Response]]
T = typing.TypeVar("T")
class _CachedRequest(Request):
"""
If the user calls Request.body() from their dispatch function
we cache the entire request body in memory and pass that to downstream middlewares,
but if they call Request.stream() then all we do is send an
empty body so that downstream things don't hang forever.
"""
def __init__(self, scope: Scope, receive: Receive):
super().__init__(scope, receive)
self._wrapped_rcv_disconnected = False
self._wrapped_rcv_consumed = False
self._wrapped_rc_stream = self.stream()
async def wrapped_receive(self) -> Message:
# wrapped_rcv state 1: disconnected
if self._wrapped_rcv_disconnected:
# we've already sent a disconnect to the downstream app
# we don't need to wait to get another one
# (although most ASGI servers will just keep sending it)
return {"type": "http.disconnect"}
# wrapped_rcv state 1: consumed but not yet disconnected
if self._wrapped_rcv_consumed:
# since the downstream app has consumed us all that is left
# is to send it a disconnect
if self._is_disconnected:
# the middleware has already seen the disconnect
# since we know the client is disconnected no need to wait
# for the message
self._wrapped_rcv_disconnected = True
return {"type": "http.disconnect"}
# we don't know yet if the client is disconnected or not
# so we'll wait until we get that message
msg = await self.receive()
if msg["type"] != "http.disconnect": # pragma: no cover
# at this point a disconnect is all that we should be receiving
# if we get something else, things went wrong somewhere
raise RuntimeError(f"Unexpected message received: {msg['type']}")
self._wrapped_rcv_disconnected = True
return msg
# wrapped_rcv state 3: not yet consumed
if getattr(self, "_body", None) is not None:
# body() was called, we return it even if the client disconnected
self._wrapped_rcv_consumed = True
return {
"type": "http.request",
"body": self._body,
"more_body": False,
}
elif self._stream_consumed:
# stream() was called to completion
# return an empty body so that downstream apps don't hang
# waiting for a disconnect
self._wrapped_rcv_consumed = True
return {
"type": "http.request",
"body": b"",
"more_body": False,
}
else:
# body() was never called and stream() wasn't consumed
try:
stream = self.stream()
chunk = await stream.__anext__()
self._wrapped_rcv_consumed = self._stream_consumed
return {
"type": "http.request",
"body": chunk,
"more_body": not self._stream_consumed,
}
except ClientDisconnect:
self._wrapped_rcv_disconnected = True
return {"type": "http.disconnect"}
class BaseHTTPMiddleware:
def __init__(self, app: ASGIApp, dispatch: DispatchFunction | None = None) -> None:
self.app = app
self.dispatch_func = self.dispatch if dispatch is None else dispatch
async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
if scope["type"] != "http":
await self.app(scope, receive, send)
return
request = _CachedRequest(scope, receive)
wrapped_receive = request.wrapped_receive
response_sent = anyio.Event()
app_exc: Exception | None = None
async def call_next(request: Request) -> Response:
async def receive_or_disconnect() -> Message:
if response_sent.is_set():
return {"type": "http.disconnect"}
async with anyio.create_task_group() as task_group:
async def wrap(func: typing.Callable[[], typing.Awaitable[T]]) -> T:
result = await func()
task_group.cancel_scope.cancel()
return result
task_group.start_soon(wrap, response_sent.wait)
message = await wrap(wrapped_receive)
if response_sent.is_set():
return {"type": "http.disconnect"}
return message
async def send_no_error(message: Message) -> None:
try:
await send_stream.send(message)
except anyio.BrokenResourceError:
# recv_stream has been closed, i.e. response_sent has been set.
return
async def coro() -> None:
nonlocal app_exc
with send_stream:
try:
await self.app(scope, receive_or_disconnect, send_no_error)
except Exception as exc:
app_exc = exc
task_group.start_soon(coro)
try:
message = await recv_stream.receive()
info = message.get("info", None)
if message["type"] == "http.response.debug" and info is not None:
message = await recv_stream.receive()
except anyio.EndOfStream:
if app_exc is not None:
raise app_exc
raise RuntimeError("No response returned.")
assert message["type"] == "http.response.start"
async def body_stream() -> typing.AsyncGenerator[bytes, None]:
async for message in recv_stream:
assert message["type"] == "http.response.body"
body = message.get("body", b"")
if body:
yield body
if not message.get("more_body", False):
break
response = _StreamingResponse(status_code=message["status"], content=body_stream(), info=info)
response.raw_headers = message["headers"]
return response
streams: anyio.create_memory_object_stream[Message] = anyio.create_memory_object_stream()
send_stream, recv_stream = streams
with recv_stream, send_stream, collapse_excgroups():
async with anyio.create_task_group() as task_group:
response = await self.dispatch_func(request, call_next)
await response(scope, wrapped_receive, send)
response_sent.set()
recv_stream.close()
if app_exc is not None:
raise app_exc
async def dispatch(self, request: Request, call_next: RequestResponseEndpoint) -> Response:
raise NotImplementedError() # pragma: no cover
class _StreamingResponse(Response):
def __init__(
self,
content: AsyncContentStream,
status_code: int = 200,
headers: typing.Mapping[str, str] | None = None,
media_type: str | None = None,
info: typing.Mapping[str, typing.Any] | None = None,
) -> None:
self.info = info
self.body_iterator = content
self.status_code = status_code
self.media_type = media_type
self.init_headers(headers)
self.background = None
async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
if self.info is not None:
await send({"type": "http.response.debug", "info": self.info})
await send(
{
"type": "http.response.start",
"status": self.status_code,
"headers": self.raw_headers,
}
)
async for chunk in self.body_iterator:
await send({"type": "http.response.body", "body": chunk, "more_body": True})
await send({"type": "http.response.body", "body": b"", "more_body": False})
if self.background:
await self.background()
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