Ignore writing headers when in ASGI mode (#1957)

* Ignore writing headers when in ASGI mode for streaming responses

* Move asgi set on streaming until after response type check

* Adds multidict==5.0.0 to pass tests

* Bump version to 20.9.1

examples/run_asgi.py

@@ -7,8 +7,8 @@
 """
 
 from pathlib import Path
-from sanic import Sanic, response
 
+from sanic import Sanic, response
 
 app = Sanic(__name__)
 
@@ -42,9 +42,7 @@ async def handler_file(request):
 
 @app.route("/file_stream")
 async def handler_file_stream(request):
-    return await response.file_stream(
-        Path("../") / "setup.py", chunk_size=1024
-    )
+    return await response.file_stream(Path("../") / "setup.py", chunk_size=1024)
 
 
 @app.route("/stream", stream=True)

sanic/__version__.py

@@ -1 +1 @@
-__version__ = "20.9.0"
+__version__ = "20.9.1"

sanic/asgi.py

@@ -350,6 +350,8 @@ async def stream_callback(self, response: HTTPResponse) -> None:
                 if name not in (b"Set-Cookie",)
             ]
 
+        response.asgi = True
+
         if "content-length" not in response.headers and not isinstance(
             response, StreamingHTTPResponse
         ):

sanic/response.py

@@ -22,6 +22,9 @@
 
 
 class BaseHTTPResponse:
+    def __init__(self):
+        self.asgi = False
+
     def _encode_body(self, data):
         return data.encode() if hasattr(data, "encode") else data
 
@@ -80,6 +83,8 @@ def __init__(
         content_type="text/plain; charset=utf-8",
         chunked=True,
     ):
+        super().__init__()
+
         self.content_type = content_type
         self.streaming_fn = streaming_fn
         self.status = status
@@ -109,13 +114,14 @@ async def stream(
         """
         if version != "1.1":
             self.chunked = False
-        headers = self.get_headers(
-            version,
-            keep_alive=keep_alive,
-            keep_alive_timeout=keep_alive_timeout,
-        )
-        await self.protocol.push_data(headers)
-        await self.protocol.drain()
+        if not getattr(self, "asgi", False):
+            headers = self.get_headers(
+                version,
+                keep_alive=keep_alive,
+                keep_alive_timeout=keep_alive_timeout,
+            )
+            await self.protocol.push_data(headers)
+            await self.protocol.drain()
         await self.streaming_fn(self)
         if self.chunked:
             await self.protocol.push_data(b"0\r\n\r\n")
@@ -143,6 +149,8 @@ def __init__(
         content_type=None,
         body_bytes=b"",
     ):
+        super().__init__()
+
         self.content_type = content_type
         self.body = body_bytes if body is None else self._encode_body(body)
         self.status = status

tests/test_response.py

@@ -235,13 +235,29 @@ def test_chunked_streaming_returns_correct_content(streaming_app):
     assert response.text == "foo,bar"
 
 
+@pytest.mark.asyncio
+async def test_chunked_streaming_returns_correct_content_asgi(streaming_app):
+    request, response = await streaming_app.asgi_client.get("/")
+    assert response.text == "4\r\nfoo,\r\n3\r\nbar\r\n0\r\n\r\n"
+
+
 def test_non_chunked_streaming_adds_correct_headers(non_chunked_streaming_app):
     request, response = non_chunked_streaming_app.test_client.get("/")
     assert "Transfer-Encoding" not in response.headers
     assert response.headers["Content-Type"] == "text/csv"
     assert response.headers["Content-Length"] == "7"
 
 
+@pytest.mark.asyncio
+async def test_non_chunked_streaming_adds_correct_headers_asgi(
+    non_chunked_streaming_app,
+):
+    request, response = await non_chunked_streaming_app.asgi_client.get("/")
+    assert "Transfer-Encoding" not in response.headers
+    assert response.headers["Content-Type"] == "text/csv"
+    assert response.headers["Content-Length"] == "7"
+
+
 def test_non_chunked_streaming_returns_correct_content(
     non_chunked_streaming_app,
 ):