Repository: aio-libs/aiohttp

Issue:
Server returns 400: "invalid character in chunk size header" for valid request
🐞 **Describe the bug**
When server ignores content of request with `Transfer-Encoding: chunked`, parsing of next request can fail.

💡 **To Reproduce**

The following script:

```
import asyncio

from aiohttp import web, ClientSession


async def start_server():
    async def hello(request):
        return web.Response(text="OK", status=200)

    app = web.Application()
    app.add_routes([web.get('/', hello)])
    app.add_routes([web.put('/', hello)])

    runner = web.AppRunner(app)
    await runner.setup()
    site = web.TCPSite(runner, 'localhost', 8080)
    await site.start()


async def main():
    await start_server()

    async def data_gen():
        for _ in range(10):
            yield b'just data'
            await asyncio.sleep(0.1)  # Make sending of content slow

    async with ClientSession() as session:
        while True:
            # Do put
            async with session.put("http://localhost:8080", data=data_gen()):
                pass
            # Do get
            async with session.get("http://localhost:8080") as resp:
                if resp.status != 200:
                    print("failed with status: ", resp.status)
                    print("content is: ", await resp.content.read())
                    return
            await asyncio.sleep(0.1)

asyncio.run(main())
```

Prints the following:

```
$ python3 reproduce.py 
Error handling request
Traceback (most recent call last):
  File ".../venv/lib/python3.7/site-packages/aiohttp/web_protocol.py", line 315, in data_received
    messages, upgraded, tail = self._request_parser.feed_data(data)
  File "aiohttp/_http_parser.pyx", line 546, in aiohttp._http_parser.HttpParser.feed_data
aiohttp.http_exceptions.BadHttpMessage: 400, message='invalid character in chunk size header'
failed with status:  400
content is:  b'invalid character in chunk size header'
```

If I add `await request.content.read()`, the problem disappears.


💡 **Expected behavior**

Server should not fail to parse valid request.


📋 **Your version of the Python**
<!-- Attach your version of the Python. -->
```console
$ python --version
Python 3.7.9
```

📋 **Your version of the aiohttp/yarl/multidict distributions**
<!-- Attach your version of the distributions in the code blocks below. -->
```console
$ python -m pip show aiohttp
Name: aiohttp
Version: 3.7.2
...
```
```console
$ python -m pip show multidict
Name: multidict
Version: 4.7.6
...
```
```console
$ python -m pip show yarl
Name: yarl
Version: 1.6.2
...
```



Discussion:
Thanks for the reproducer.
I recall bug reports that sound similar to your issue but they have a lack of details; your script definitely can help with pinning the problem down.
I suspect `web_protocol.py` doesn't close the socket if a web-handler is done but the socket has an unread part of the processed request's body. It screws up the HTTP parser easily.
I've reprduced this issue with
```python
async def test_5220(aiohttp_client) -> None:
    async def handler(request):
        return web.Response(text="OK", status=200)

    app = web.Application()
    app.add_routes([web.get("/", handler)])
    app.add_routes([web.put("/", handler)])

    client = await aiohttp_client(app)

    async def data_gen():
        for _ in range(10):
            yield b"just data"
            await asyncio.sleep(0.1)

    async with client.put("/", data=data_gen(), raise_for_status=True):
        pass
    async with client.get("/", raise_for_status=True):
        pass
```

```pytb
ERROR    aiohttp.server:web_protocol.py:425 Error handling request
Traceback (most recent call last):
  File "/home/dmitry/Sources/aiohttp/aiohttp/web_protocol.py", line 345, in data_received
    messages, upgraded, tail = self._request_parser.feed_data(data)
  File "aiohttp/_http_parser.pyx", line 546, in aiohttp._http_parser.HttpParser.feed_data
    raise ex
aiohttp.http_exceptions.BadHttpMessage: 400, message='invalid character in chunk size header'
```


This is the packets dump [dump.pcapng.gz](https://github.com/aio-libs/aiohttp/files/5540354/dump.pcapng.gz)
Looks like a client continues to execute PUT **after** it starts to execute GET.

This issue is really tricky.

I'll try to explain what is happening! 

First of all `put` request is `chunked` because of the `data=data_gen()` argument. Here is what the first portion of data looks like:
```
PUT / HTTP/1.1
Host: localhost:8080
Accept: */*
Accept-Encoding: gzip, deflate
User-Agent: Python/3.8 aiohttp/4.0.0a1
Content-Type: application/octet-stream
Transfer-Encoding: chunked

9
just data
```
After sending this data client quits, but the connection is not closed, because according to HTTP 1.1 connections are `keep-alive` by default. 
Here's where the first problem comes in, client didn't send termination byte `b'0'` before closing.

On the server side, however, this wouldn't be an issue if `lingering` mechanism wasn't enabled by default.
`lingering` was introduced in #1050. Its entire idea is in reading from socket **after** the handler is over, to prevent errors on client side (read more in original PR).

So as you may have guessed, when client starts `get` request, server is still in `lingering` state with a parser waiting for the next chunk of data or `b'0'` from previous request :(

I've tried to fix this in #5238

@greshilov thanks for digging into the problem.

I think the #5238 fixes the incorrect side.  
Maybe it makes sense (let me double-check the PR) but I believe that the server should correctly process even such "malformed" requests as we have in reproducers above.

Reviewing the `web_protocol.py` code I found that lingering_time handling (written by myself BTW) is buggy and can be improved.  During writing a patch I've figured out that the whole protocol class can be significantly improved and simplified.
Thanks to #4771 both master and 3.8 versions of this file are almost identical, the change can be backported easily.

So, my plan is:
1. Refactor error handling to avoid spawning a task for `handle_parse_error()` but push a special "error" message into `self._messages` and process it in a normal way.  Working with two potentially concurrent tasks (one for regular request handling and another one for parser error processing is hard).
2. Move the lingering code into the recently added `finish_response()` method; always use the method for response sending and half-closing with dropping the connection after a timeout as RFC 7230 suggests (https://github.com/aio-libs/aiohttp/pull/1050).
Ref: https://github.com/aio-libs/aiohttp/issues/5269.
@asvetlov glad to hear! In addition to the new correct behaviour on server, shouldn't we protect aiohttp client users in such cases?

```
async with client.put("/", data=data_gen(), raise_for_status=True):
        pass
#   <-- At this point, after the context manager is over, client is still connected and has uncompleted request!
```
I think on both sides we should drop the connection even if keepalive is enabled but the payload was not fully read. The only difference is that on the server side halfclose-lingering-closing should be used. The client can just drop immediately.
> I think on both sides we should drop the connection even if keepalive is enabled but the payload was not fully read. The only difference is that on the server side halfclose-lingering-closing should be used. The client can just drop immediately.

> Is there a ready-made solution for this problem now? I also encountered the same problem。
https://github.com/aio-libs/aiohttp/issues/5443#issue-795171239
IMHO,  if this issue is not easy to be fixed,  then [the workaround](https://github.com/aio-libs/aiohttp/issues/5269#issuecomment-851347692) about `os.environ.setdefault('AIOHTTP_NO_EXTENSIONS', '1')` should be added by default.
I don't see how that's relevant...
@Dreamsorcerer Sorry, I added the related post now.
Still not sure how that's relevant. That is an issue with there actually being an invalid character in header (when read client-side), which is closed because we've enabled lenient options on the llhttp parser (though, currently may still be an issue if a response doesn't use CRLF for the line breaks: https://github.com/nodejs/llhttp/issues/241). This is an issue about reading from a keep-alive connection that should have been closed (on the server-side).
Thank you for your explanation. I agree with you now. It was me who confused these two issues. Should I delete my posts or just keep them here?

Resolving patch:
diff --git a/aiohttp/client.py b/aiohttp/client.py
--- a/aiohttp/client.py
+++ b/aiohttp/client.py
@@ -1140,6 +1140,7 @@ async def __aexit__(
         # explicitly.  Otherwise connection error handling should kick in
         # and close/recycle the connection as required.
         self._resp.release()
+        await self._resp.wait_for_close()
 
 
 class _WSRequestContextManager(_BaseRequestContextManager[ClientWebSocketResponse]):
diff --git a/aiohttp/client_reqrep.py b/aiohttp/client_reqrep.py
--- a/aiohttp/client_reqrep.py
+++ b/aiohttp/client_reqrep.py
@@ -529,8 +529,11 @@ async def write_bytes(
         """Support coroutines that yields bytes objects."""
         # 100 response
         if self._continue is not None:
-            await writer.drain()
-            await self._continue
+            try:
+                await writer.drain()
+                await self._continue
+            except asyncio.CancelledError:
+                return
 
         protocol = conn.protocol
         assert protocol is not None
@@ -543,8 +546,6 @@ async def write_bytes(
 
                 for chunk in self.body:
                     await writer.write(chunk)  # type: ignore[arg-type]
-
-            await writer.write_eof()
         except OSError as exc:
             if exc.errno is None and isinstance(exc, asyncio.TimeoutError):
                 protocol.set_exception(exc)
@@ -555,12 +556,12 @@ async def write_bytes(
                 new_exc.__context__ = exc
                 new_exc.__cause__ = exc
                 protocol.set_exception(new_exc)
-        except asyncio.CancelledError as exc:
-            if not conn.closed:
-                protocol.set_exception(exc)
+        except asyncio.CancelledError:
+            await writer.write_eof()
         except Exception as exc:
             protocol.set_exception(exc)
         else:
+            await writer.write_eof()
             protocol.start_timeout()
         finally:
             self._writer = None
@@ -649,7 +650,8 @@ async def send(self, conn: "Connection") -> "ClientResponse":
     async def close(self) -> None:
         if self._writer is not None:
             try:
-                await self._writer
+                with contextlib.suppress(asyncio.CancelledError):
+                    await self._writer
             finally:
                 self._writer = None
 
@@ -914,8 +916,7 @@ def _response_eof(self) -> None:
             ):
                 return
 
-            self._connection.release()
-            self._connection = None
+            self._release_connection()
 
         self._closed = True
         self._cleanup_writer()
@@ -927,30 +928,22 @@ def closed(self) -> bool:
     def close(self) -> None:
         if not self._released:
             self._notify_content()
-        if self._closed:
-            return
 
         self._closed = True
         if self._loop.is_closed():
             return
 
-        if self._connection is not None:
-            self._connection.close()
-            self._connection = None
         self._cleanup_writer()
+        self._release_connection()
 
     def release(self) -> Any:
         if not self._released:
             self._notify_content()
-        if self._closed:
-            return noop()
 
         self._closed = True
-        if self._connection is not None:
-            self._connection.release()
-            self._connection = None
 
         self._cleanup_writer()
+        self._release_connection()
         return noop()
 
     @property
@@ -975,10 +968,28 @@ def raise_for_status(self) -> None:
                 headers=self.headers,
             )
 
+    def _release_connection(self) -> None:
+        if self._connection is not None:
+            if self._writer is None:
+                self._connection.release()
+                self._connection = None
+            else:
+                self._writer.add_done_callback(lambda f: self._release_connection())
+
+    async def _wait_released(self) -> None:
+        if self._writer is not None:
+            try:
+                await self._writer
+            finally:
+                self._writer = None
+        self._release_connection()
+
     def _cleanup_writer(self) -> None:
         if self._writer is not None:
-            self._writer.cancel()
-        self._writer = None
+            if self._writer.done():
+                self._writer = None
+            else:
+                self._writer.cancel()
         self._session = None
 
     def _notify_content(self) -> None:
@@ -1008,9 +1019,10 @@ async def read(self) -> bytes:
             except BaseException:
                 self.close()
                 raise
-        elif self._released:
+        elif self._released:  # Response explicity released
             raise ClientConnectionError("Connection closed")
 
+        await self._wait_released()  # Underlying connection released
         return self._body
 
     def get_encoding(self) -> str:
@@ -1087,3 +1099,4 @@ async def __aexit__(
         # for exceptions, response object can close connection
         # if state is broken
         self.release()
+        await self.wait_for_close()


Test patch:
diff --git a/tests/test_client_functional.py b/tests/test_client_functional.py
--- a/tests/test_client_functional.py
+++ b/tests/test_client_functional.py
@@ -137,6 +137,7 @@ async def handler(request):
     client = await aiohttp_client(app)
     resp = await client.get("/")
     assert resp.closed
+    await resp.wait_for_close()
     assert 1 == len(client._session.connector._conns)
 
 
@@ -156,6 +157,60 @@ async def handler(request):
     assert content == b""
 
 
+async def test_stream_request_on_server_eof(aiohttp_client) -> None:
+    async def handler(request):
+        return web.Response(text="OK", status=200)
+
+    app = web.Application()
+    app.add_routes([web.get("/", handler)])
+    app.add_routes([web.put("/", handler)])
+
+    client = await aiohttp_client(app)
+
+    async def data_gen():
+        for _ in range(2):
+            yield b"just data"
+            await asyncio.sleep(0.1)
+
+    async with client.put("/", data=data_gen()) as resp:
+        assert 200 == resp.status
+        assert len(client.session.connector._acquired) == 1
+        conn = next(iter(client.session.connector._acquired))
+
+    async with client.get("/") as resp:
+        assert 200 == resp.status
+
+    # Connection should have been reused
+    conns = next(iter(client.session.connector._conns.values()))
+    assert len(conns) == 1
+    assert conns[0][0] is conn
+
+
+async def test_stream_request_on_server_eof_nested(aiohttp_client) -> None:
+    async def handler(request):
+        return web.Response(text="OK", status=200)
+
+    app = web.Application()
+    app.add_routes([web.get("/", handler)])
+    app.add_routes([web.put("/", handler)])
+
+    client = await aiohttp_client(app)
+
+    async def data_gen():
+        for _ in range(2):
+            yield b"just data"
+            await asyncio.sleep(0.1)
+
+    async with client.put("/", data=data_gen()) as resp:
+        assert 200 == resp.status
+        async with client.get("/") as resp:
+            assert 200 == resp.status
+
+    # Should be 2 separate connections
+    conns = next(iter(client.session.connector._conns.values()))
+    assert len(conns) == 2
+
+
 async def test_HTTP_304_WITH_BODY(aiohttp_client: Any) -> None:
     async def handler(request):
         body = await request.read()
@@ -238,8 +293,8 @@ async def handler(request):
     client = await aiohttp_client(app)
 
     with io.BytesIO(data) as file_handle:
-        resp = await client.post("/", data=file_handle)
-    assert 200 == resp.status
+        async with client.post("/", data=file_handle) as resp:
+            assert 200 == resp.status
 
 
 async def test_post_data_with_bytesio_file(aiohttp_client: Any) -> None:
diff --git a/tests/test_client_response.py b/tests/test_client_response.py
--- a/tests/test_client_response.py
+++ b/tests/test_client_response.py
@@ -18,6 +18,14 @@
 from aiohttp.test_utils import make_mocked_coro
 
 
+class WriterMock(mock.AsyncMock):
+    def __await__(self) -> None:
+        return self().__await__()
+
+    def done(self) -> bool:
+        return True
+
+
 @pytest.fixture
 def session():
     return mock.Mock()
@@ -30,7 +38,7 @@ async def test_http_processing_error(session: Any) -> None:
         "get",
         URL("http://del-cl-resp.org"),
         request_info=request_info,
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -58,7 +66,7 @@ def test_del(session: Any) -> None:
         "get",
         URL("http://del-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -85,7 +93,7 @@ def test_close(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -106,7 +114,7 @@ def test_wait_for_100_1(loop: Any, session: Any) -> None:
         URL("http://python.org"),
         continue100=object(),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         timer=TimerNoop(),
         traces=[],
         loop=loop,
@@ -122,7 +130,7 @@ def test_wait_for_100_2(loop: Any, session: Any) -> None:
         URL("http://python.org"),
         request_info=mock.Mock(),
         continue100=None,
-        writer=mock.Mock(),
+        writer=WriterMock(),
         timer=TimerNoop(),
         traces=[],
         loop=loop,
@@ -137,7 +145,7 @@ def test_repr(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -154,7 +162,7 @@ def test_repr_non_ascii_url() -> None:
         "get",
         URL("http://fake-host.org/\u03bb"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -169,7 +177,7 @@ def test_repr_non_ascii_reason() -> None:
         "get",
         URL("http://fake-host.org/path"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -187,7 +195,7 @@ async def test_read_and_release_connection(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -213,7 +221,7 @@ async def test_read_and_release_connection_with_error(loop: Any, session: Any) -
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -234,7 +242,7 @@ async def test_release(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -263,7 +271,7 @@ def run(conn):
             "get",
             URL("http://def-cl-resp.org"),
             request_info=mock.Mock(),
-            writer=mock.Mock(),
+            writer=WriterMock(),
             continue100=None,
             timer=TimerNoop(),
             traces=[],
@@ -283,7 +291,7 @@ async def test_response_eof(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=None,
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -304,7 +312,7 @@ async def test_response_eof_upgraded(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -325,7 +333,7 @@ async def test_response_eof_after_connection_detach(loop: Any, session: Any) ->
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=None,
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -346,7 +354,7 @@ async def test_text(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -373,7 +381,7 @@ async def test_text_bad_encoding(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -403,7 +411,7 @@ async def test_text_custom_encoding(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -436,7 +444,7 @@ async def test_text_charset_resolver(
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -465,7 +473,7 @@ async def test_get_encoding_body_none(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -495,7 +503,7 @@ async def test_text_after_read(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -522,7 +530,7 @@ async def test_json(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -549,7 +557,7 @@ async def test_json_extended_content_type(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -578,7 +586,7 @@ async def test_json_custom_content_type(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -605,7 +613,7 @@ async def test_json_custom_loader(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -627,7 +635,7 @@ async def test_json_invalid_content_type(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -648,7 +656,7 @@ async def test_json_no_content(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -667,7 +675,7 @@ async def test_json_override_encoding(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -696,7 +704,7 @@ def test_get_encoding_unknown(loop: Any, session: Any) -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -713,7 +721,7 @@ def test_raise_for_status_2xx() -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -730,7 +738,7 @@ def test_raise_for_status_4xx() -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -751,7 +759,7 @@ def test_raise_for_status_4xx_without_reason() -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -772,7 +780,7 @@ def test_resp_host() -> None:
         "get",
         URL("http://del-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -787,7 +795,7 @@ def test_content_type() -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -804,7 +812,7 @@ def test_content_type_no_header() -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -821,7 +829,7 @@ def test_charset() -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -838,7 +846,7 @@ def test_charset_no_header() -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -855,7 +863,7 @@ def test_charset_no_charset() -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -872,7 +880,7 @@ def test_content_disposition_full() -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -895,7 +903,7 @@ def test_content_disposition_no_parameters() -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -914,7 +922,7 @@ def test_content_disposition_no_header() -> None:
         "get",
         URL("http://def-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -933,7 +941,7 @@ def test_response_request_info() -> None:
         "get",
         URL(url),
         request_info=RequestInfo(url, "get", headers, url),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -952,7 +960,7 @@ def test_request_info_in_exception() -> None:
         "get",
         URL(url),
         request_info=RequestInfo(url, "get", headers, url),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -973,7 +981,7 @@ def test_no_redirect_history_in_exception() -> None:
         "get",
         URL(url),
         request_info=RequestInfo(url, "get", headers, url),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -996,7 +1004,7 @@ def test_redirect_history_in_exception() -> None:
         "get",
         URL(url),
         request_info=RequestInfo(url, "get", headers, url),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -1010,7 +1018,7 @@ def test_redirect_history_in_exception() -> None:
         "get",
         URL(hist_url),
         request_info=RequestInfo(url, "get", headers, url),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -1039,7 +1047,7 @@ async def test_response_read_triggers_callback(loop: Any, session: Any) -> None:
         response_method,
         response_url,
         request_info=mock.Mock,
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         loop=loop,
@@ -1072,7 +1080,7 @@ def test_response_real_url(loop: Any, session: Any) -> None:
         "get",
         url,
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -1089,7 +1097,7 @@ def test_response_links_comma_separated(loop: Any, session: Any) -> None:
         "get",
         url,
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -1119,7 +1127,7 @@ def test_response_links_multiple_headers(loop: Any, session: Any) -> None:
         "get",
         url,
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -1144,7 +1152,7 @@ def test_response_links_no_rel(loop: Any, session: Any) -> None:
         "get",
         url,
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -1163,7 +1171,7 @@ def test_response_links_quoted(loop: Any, session: Any) -> None:
         "get",
         url,
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -1186,7 +1194,7 @@ def test_response_links_relative(loop: Any, session: Any) -> None:
         "get",
         url,
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -1209,7 +1217,7 @@ def test_response_links_empty(loop: Any, session: Any) -> None:
         "get",
         url,
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
@@ -1225,7 +1233,7 @@ def test_response_not_closed_after_get_ok(mocker) -> None:
         "get",
         URL("http://del-cl-resp.org"),
         request_info=mock.Mock(),
-        writer=mock.Mock(),
+        writer=WriterMock(),
         continue100=None,
         timer=TimerNoop(),
         traces=[],
diff --git a/tests/test_proxy_functional.py b/tests/test_proxy_functional.py
--- a/tests/test_proxy_functional.py
+++ b/tests/test_proxy_functional.py
@@ -407,7 +407,8 @@ async def test_proxy_http_acquired_cleanup(proxy_test_server: Any, loop: Any) ->
 
     assert 0 == len(conn._acquired)
 
-    resp = await sess.get(url, proxy=proxy.url)
+    async with sess.get(url, proxy=proxy.url) as resp:
+        pass
     assert resp.closed
 
     assert 0 == len(conn._acquired)
diff --git a/tests/test_web_functional.py b/tests/test_web_functional.py
--- a/tests/test_web_functional.py
+++ b/tests/test_web_functional.py
@@ -1816,7 +1816,6 @@ async def handler(request):
     resp = await session.get(server.make_url("/"))
     async with resp:
         assert resp.status == 200
-        assert resp.connection is None
     assert resp.connection is None
 
     await session.close()