From a40aa2c87f3eecc71a564139781914e205a51a32 Mon Sep 17 00:00:00 2001
From: pgjones <philip.graham.jones@googlemail.com>
Date: Mon, 27 May 2024 17:52:22 +0100
Subject: [PATCH] Allow sending of the response before body data arrives

This was an ASGI specification condition that has now been relaxed.
---
 src/hypercorn/protocol/http_stream.py | 25 ++++++++++---------------
 tests/protocol/test_http_stream.py    | 13 +------------
 2 files changed, 11 insertions(+), 27 deletions(-)

diff --git a/src/hypercorn/protocol/http_stream.py b/src/hypercorn/protocol/http_stream.py
index 1a68cdc5..7183854b 100644
--- a/src/hypercorn/protocol/http_stream.py
+++ b/src/hypercorn/protocol/http_stream.py
@@ -141,6 +141,15 @@ async def app_send(self, message: Optional[ASGISendEvent]) -> None:
         else:
             if message["type"] == "http.response.start" and self.state == ASGIHTTPState.REQUEST:
                 self.response = message
+                headers = build_and_validate_headers(self.response.get("headers", []))
+                await self.send(
+                    Response(
+                        stream_id=self.stream_id,
+                        headers=headers,
+                        status_code=int(self.response["status"]),
+                    )
+                )
+                self.state = ASGIHTTPState.RESPONSE
             elif (
                 message["type"] == "http.response.push"
                 and self.scope["http_version"] in PUSH_VERSIONS
@@ -175,21 +184,7 @@ async def app_send(self, message: Optional[ASGISendEvent]) -> None:
                         status_code=103,
                     )
                 )
-            elif message["type"] == "http.response.body" and self.state in {
-                ASGIHTTPState.REQUEST,
-                ASGIHTTPState.RESPONSE,
-            }:
-                if self.state == ASGIHTTPState.REQUEST:
-                    headers = build_and_validate_headers(self.response.get("headers", []))
-                    await self.send(
-                        Response(
-                            stream_id=self.stream_id,
-                            headers=headers,
-                            status_code=int(self.response["status"]),
-                        )
-                    )
-                    self.state = ASGIHTTPState.RESPONSE
-
+            elif message["type"] == "http.response.body" and self.state == ASGIHTTPState.RESPONSE:
                 if (
                     not suppress_body(self.scope["method"], int(self.response["status"]))
                     and message.get("body", b"") != b""
diff --git a/tests/protocol/test_http_stream.py b/tests/protocol/test_http_stream.py
index 5518c8b9..3deb4054 100644
--- a/tests/protocol/test_http_stream.py
+++ b/tests/protocol/test_http_stream.py
@@ -165,9 +165,7 @@ async def test_send_response(stream: HTTPStream) -> None:
     await stream.app_send(
         cast(HTTPResponseStartEvent, {"type": "http.response.start", "status": 200, "headers": []})
     )
-    assert stream.state == ASGIHTTPState.REQUEST
-    # Must wait for response before sending anything
-    stream.send.assert_not_called()  # type: ignore
+    assert stream.state == ASGIHTTPState.RESPONSE
     await stream.app_send(
         cast(HTTPResponseBodyEvent, {"type": "http.response.body", "body": b"Body"})
     )
@@ -413,15 +411,6 @@ async def test_closure(stream: HTTPStream) -> None:
     assert stream.app_put.call_args_list == [call({"type": "http.disconnect"})]
 
 
-@pytest.mark.asyncio
-async def test_closed_app_send_noop(stream: HTTPStream) -> None:
-    stream.closed = True
-    await stream.app_send(
-        cast(HTTPResponseStartEvent, {"type": "http.response.start", "status": 200, "headers": []})
-    )
-    stream.send.assert_not_called()  # type: ignore
-
-
 @pytest.mark.asyncio
 async def test_abnormal_close_logging() -> None:
     config = Config()