The wrapped receive() did not return anything. (#1698)

We wrapped the receive() callback of all ASGI middleware to create spans when they where executed.
The receive() callback is used to receive message from the server.

But we forgot to return the value that the original receive() callback returns. So basically swallowing the return of the server.

Refs #1696

sentry_sdk/integrations/starlette.py

@@ -106,7 +106,7 @@ async def _sentry_receive(*args, **kwargs):
                         description=receive.__qualname__,
                     ) as span:
                         span.set_tag("starlette.middleware_name", middleware_name)
-                        await receive(*args, **kwargs)
+                        return await receive(*args, **kwargs)
 
                 receive_patched = receive.__name__ == "_sentry_receive"
                 new_receive = _sentry_receive if not receive_patched else receive
@@ -119,15 +119,15 @@ async def _sentry_send(*args, **kwargs):
                         op=OP.MIDDLEWARE_STARLETTE_SEND, description=send.__qualname__
                     ) as span:
                         span.set_tag("starlette.middleware_name", middleware_name)
-                        await send(*args, **kwargs)
+                        return await send(*args, **kwargs)
 
                 send_patched = send.__name__ == "_sentry_send"
                 new_send = _sentry_send if not send_patched else send
 
-                await old_call(app, scope, new_receive, new_send, **kwargs)
+                return await old_call(app, scope, new_receive, new_send, **kwargs)
 
         else:
-            await old_call(app, scope, receive, send, **kwargs)
+            return await old_call(app, scope, receive, send, **kwargs)
 
     not_yet_patched = old_call.__name__ not in [
         "_create_span_call",

tests/integrations/starlette/test_starlette.py

@@ -174,6 +174,21 @@ async def do_stuff(message):
         await self.app(scope, receive, do_stuff)
 
 
+class SampleReceiveSendMiddleware:
+    def __init__(self, app):
+        self.app = app
+
+    async def __call__(self, scope, receive, send):
+        message = await receive()
+        assert message
+        assert message["type"] == "http.request"
+
+        send_output = await send({"type": "something-unimportant"})
+        assert send_output is None
+
+        await self.app(scope, receive, send)
+
+
 @pytest.mark.asyncio
 async def test_starlettrequestextractor_content_length(sentry_init):
     with mock.patch(
@@ -644,6 +659,25 @@ def test_middleware_callback_spans(sentry_init, capture_events):
         idx += 1
 
 
+@pytest.mark.asyncio
+async def test_middleware_receive_send(sentry_init, capture_events):
+    sentry_init(
+        traces_sample_rate=1.0,
+        integrations=[StarletteIntegration()],
+    )
+    starlette_app = starlette_app_factory(
+        middleware=[Middleware(SampleReceiveSendMiddleware)]
+    )
+
+    client = TestClient(starlette_app, raise_server_exceptions=False)
+    try:
+        # NOTE: the assert statements checking
+        # for correct behaviour are in `SampleReceiveSendMiddleware`!
+        client.get("/message", auth=("Gabriela", "hello123"))
+    except Exception:
+        pass
+
+
 def test_last_event_id(sentry_init, capture_events):
     sentry_init(
         integrations=[StarletteIntegration()],