Changes after @Dreamsorcerer's review

aiohttp/connector.py

@@ -1085,18 +1085,14 @@ async def _start_tls_connection(
         # maintainability-wise but this is to be solved separately.
         sslcontext = cast(ssl.SSLContext, self._get_ssl_context(req))
 
-        server_hostname = req.host
-        if req.server_hostname is not None:
-            server_hostname = req.server_hostname
-
         try:
             async with ceil_timeout(timeout.sock_connect):
                 try:
                     tls_transport = await self._loop.start_tls(
                         underlying_transport,
                         tls_proto,
                         sslcontext,
-                        server_hostname=server_hostname,
+                        server_hostname=req.server_hostname or req.host,
                         ssl_handshake_timeout=timeout.total,
                     )
                 except BaseException:
@@ -1178,9 +1174,7 @@ def drop_exception(fut: "asyncio.Future[List[Dict[str, Any]]]") -> None:
             host = hinfo["host"]
             port = hinfo["port"]
 
-            server_hostname = hinfo["hostname"] if sslcontext else None
-            if req.server_hostname is not None:
-                server_hostname = req.server_hostname
+            server_hostname = (req.server_hostname or hinfo["hostname"]) if sslcontext else None
 
             try:
                 transp, proto = await self._wrap_create_connection(

docs/client_reference.rst

@@ -490,8 +490,8 @@ The client session supports the context manager protocol for self closing.
 
       :param str server_hostname: Sets or overrides the hostname that the
          target server’s certificate will be matched against.
-         See `upstream documentation <https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.loop.create_connection>`_
-         for more information.
+
+         See :method:`asyncio.loop.create_connection` for more information.
 
          .. versionadded:: 3.9
 

tests/test_connector.py

@@ -9,6 +9,7 @@
 import sys
 import uuid
 from collections import deque
+from contextlib import closing
 from unittest import mock
 
 import pytest
@@ -560,35 +561,31 @@ async def certificate_error(*args, **kwargs):
 async def test_tcp_connector_server_hostname_default(loop) -> None:
     conn = aiohttp.TCPConnector(loop=loop)
 
-    conn._loop.create_connection = mock.AsyncMock()
-    conn._loop.create_connection.return_value = mock.Mock(), mock.Mock()
+    with mock.patch.object(
+        conn._loop, "create_connection", autospec=True, spec_set=True
+    ) as create_connection:
+        create_connection.return_value = mock.Mock(), mock.Mock()
 
-    req = ClientRequest("GET", URL("https://127.0.0.1:443"), loop=loop)
-
-    established_connection = await conn.connect(req, [], ClientTimeout())
-    assert (
-        conn._loop.create_connection.call_args.kwargs["server_hostname"] == "127.0.0.1"
-    )
+        req = ClientRequest("GET", URL("https://127.0.0.1:443"), loop=loop)
 
-    established_connection.close()
+        with closing(await conn.connect(req, [], ClientTimeout())):
+            assert create_connection.call_args.kwargs["server_hostname"] == "127.0.0.1"
 
 
 async def test_tcp_connector_server_hostname_override(loop) -> None:
     conn = aiohttp.TCPConnector(loop=loop)
 
-    conn._loop.create_connection = mock.AsyncMock()
-    conn._loop.create_connection.return_value = mock.Mock(), mock.Mock()
+    with mock.patch.object(
+        conn._loop, "create_connection", autospec=True, spec_set=True
+    ) as create_connection:
+        create_connection.return_value = mock.Mock(), mock.Mock()
 
-    req = ClientRequest(
-        "GET", URL("https://127.0.0.1:443"), loop=loop, server_hostname="localhost"
-    )
-
-    established_connection = await conn.connect(req, [], ClientTimeout())
-    assert (
-        conn._loop.create_connection.call_args.kwargs["server_hostname"] == "localhost"
-    )
+        req = ClientRequest(
+            "GET", URL("https://127.0.0.1:443"), loop=loop, server_hostname="localhost"
+        )
 
-    established_connection.close()
+        with closing(await conn.connect(req, [], ClientTimeout())):
+            assert create_connection.call_args.kwargs["server_hostname"] == "localhost"
 
 
 async def test_tcp_connector_multiple_hosts_errors(loop) -> None: