From 9d745e38be4c31e184fcc33b71b29db3915a182f Mon Sep 17 00:00:00 2001
From: Aaron Chong <aaronjhchong@hotmail.com>
Date: Sun, 26 Jun 2022 00:28:24 +0800
Subject: [PATCH 1/4] Shield send http.response.start from cancellation

`RuntimeError: No response returned.` is raised in BaseHTTPMiddleware
if request is disconnected, due to `task_group.cancel_scope.cancel()`
in StreamingResponse.__call__.<locals>.wrap and cancellation check in
`await checkpoint()` of MemoryObjectSendStream.send.

Let's fix this behaviour change caused by anyio integration in 0.15.0.
---
 starlette/responses.py | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/starlette/responses.py b/starlette/responses.py
index 98c8caf1b..4f2fa745b 100644
--- a/starlette/responses.py
+++ b/starlette/responses.py
@@ -240,13 +240,14 @@ async def listen_for_disconnect(self, receive: Receive) -> None:
                 break
 
     async def stream_response(self, send: Send) -> None:
-        await send(
-            {
-                "type": "http.response.start",
-                "status": self.status_code,
-                "headers": self.raw_headers,
-            }
-        )
+        with anyio.CancelScope(shield=True):
+            await send(
+                {
+                    "type": "http.response.start",
+                    "status": self.status_code,
+                    "headers": self.raw_headers,
+                }
+            )
         async for chunk in self.body_iterator:
             if not isinstance(chunk, bytes):
                 chunk = chunk.encode(self.charset)

From 260df6afaae988cab021c5fd7cc68a1175071c53 Mon Sep 17 00:00:00 2001
From: Aaron Chong <aaronjhchong@hotmail.com>
Date: Mon, 27 Jun 2022 20:00:17 +0800
Subject: [PATCH 2/4] Test StreamingResponse send http.response.start

---
 tests/test_responses.py | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/tests/test_responses.py b/tests/test_responses.py
index a272559eb..b4ec0be0a 100644
--- a/tests/test_responses.py
+++ b/tests/test_responses.py
@@ -2,6 +2,7 @@
 
 import anyio
 import pytest
+from anyio.lowlevel import checkpoint
 
 from starlette import status
 from starlette.background import BackgroundTask
@@ -14,6 +15,7 @@
     StreamingResponse,
 )
 from starlette.testclient import TestClient
+from starlette.types import Message
 
 
 def test_text_response(test_client_factory):
@@ -391,3 +393,26 @@ def test_streaming_response_known_size(test_client_factory):
     client: TestClient = test_client_factory(app)
     response = client.get("/")
     assert response.headers["content-length"] == "10"
+
+
+@pytest.mark.anyio
+async def test_streaming_response_disconnect_should_cancel_after_send_http_response_start_returns():
+    """
+    Test that StreamingResponse cancels after send "http.response.start" returns, even if there is a checkpoint in send.
+    """
+    send_to_receiver = False
+
+    async def receive() -> Message:
+        return {"type": "http.disconnect"}
+
+    async def send(msg: Message) -> None:
+        nonlocal send_to_receiver
+        assert msg["type"] == "http.response.start"
+        await checkpoint()  # await asyncio.sleep(0)
+        send_to_receiver = True
+
+    scope = {"type": "http", "method": "GET", "path": "/"}
+
+    response = StreamingResponse("")
+    await response(scope, receive, send)
+    assert send_to_receiver

From d53845c6240083aef6cea4ad7d1de102fbbe735b Mon Sep 17 00:00:00 2001
From: Aaron Chong <aaronjhchong@hotmail.com>
Date: Mon, 27 Jun 2022 21:28:28 +0800
Subject: [PATCH 3/4] Fix E501 line too long

---
 tests/test_responses.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tests/test_responses.py b/tests/test_responses.py
index b4ec0be0a..6afa5a592 100644
--- a/tests/test_responses.py
+++ b/tests/test_responses.py
@@ -396,9 +396,10 @@ def test_streaming_response_known_size(test_client_factory):
 
 
 @pytest.mark.anyio
-async def test_streaming_response_disconnect_should_cancel_after_send_http_response_start_returns():
+async def test_streaming_response_disconnect_should_cancel_after_send_start_returns():
     """
-    Test that StreamingResponse cancels after send "http.response.start" returns, even if there is a checkpoint in send.
+    Test that StreamingResponse cancels after send "http.response.start" returns,
+    even if there is a checkpoint in send.
     """
     send_to_receiver = False
 

From 11c011dd4601aaf8acd28dc1c286a49f9e7d0786 Mon Sep 17 00:00:00 2001
From: Aaron Chong <aaronjhchong@hotmail.com>
Date: Mon, 27 Jun 2022 21:44:58 +0800
Subject: [PATCH 4/4] Fix arg-type

---
 tests/test_responses.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/test_responses.py b/tests/test_responses.py
index 6afa5a592..af57288eb 100644
--- a/tests/test_responses.py
+++ b/tests/test_responses.py
@@ -414,6 +414,6 @@ async def send(msg: Message) -> None:
 
     scope = {"type": "http", "method": "GET", "path": "/"}
 
-    response = StreamingResponse("")
+    response = StreamingResponse(iter(""))
     await response(scope, receive, send)
     assert send_to_receiver