From 7e16dd198ea5042bd127a0d0417c40348ac1d158 Mon Sep 17 00:00:00 2001
From: Alexey Nikitin <30608416+NewGlad@users.noreply.github.com>
Date: Tue, 9 Apr 2024 21:50:18 +0800
Subject: [PATCH] 
 Patchback/backports/3.10/5fd29467fb63efdfae1ace280cec36b1f8139567/pr 8290
 (#8310)

---
 CHANGES/8253.bugfix          |  1 +
 CONTRIBUTORS.txt             |  1 +
 aiohttp/client.py            | 51 ++++++++++++++++++++----------------
 tests/test_client_session.py | 10 +++++++
 4 files changed, 40 insertions(+), 23 deletions(-)
 create mode 100644 CHANGES/8253.bugfix

diff --git a/CHANGES/8253.bugfix b/CHANGES/8253.bugfix
new file mode 100644
index 00000000000..91b06d9b35d
--- /dev/null
+++ b/CHANGES/8253.bugfix
@@ -0,0 +1 @@
+Fixed "Unclosed client session" when initialization of ClientSession fails -- by :user:`NewGlad`.
diff --git a/CONTRIBUTORS.txt b/CONTRIBUTORS.txt
index 6b53b5ad9c9..4442664118f 100644
--- a/CONTRIBUTORS.txt
+++ b/CONTRIBUTORS.txt
@@ -27,6 +27,7 @@ Alexander Shorin
 Alexander Travov
 Alexandru Mihai
 Alexey Firsov
+Alexey Nikitin
 Alexey Popravka
 Alexey Stepanov
 Amin Etesamian
diff --git a/aiohttp/client.py b/aiohttp/client.py
index 8d8d13f25f7..6288fb8f89c 100644
--- a/aiohttp/client.py
+++ b/aiohttp/client.py
@@ -252,6 +252,10 @@ def __init__(
         max_field_size: int = 8190,
         fallback_charset_resolver: _CharsetResolver = lambda r, b: "utf-8",
     ) -> None:
+        # We initialise _connector to None immediately, as it's referenced in __del__()
+        # and could cause issues if an exception occurs during initialisation.
+        self._connector: Optional[BaseConnector] = None
+
         if loop is None:
             if connector is not None:
                 loop = connector._loop
@@ -266,29 +270,6 @@ def __init__(
                 self._base_url.origin() == self._base_url
             ), "Only absolute URLs without path part are supported"
 
-        if connector is None:
-            connector = TCPConnector(loop=loop)
-
-        if connector._loop is not loop:
-            raise RuntimeError("Session and connector has to use same event loop")
-
-        self._loop = loop
-
-        if loop.get_debug():
-            self._source_traceback = traceback.extract_stack(sys._getframe(1))
-
-        if cookie_jar is None:
-            cookie_jar = CookieJar(loop=loop)
-        self._cookie_jar = cookie_jar
-
-        if cookies is not None:
-            self._cookie_jar.update_cookies(cookies)
-
-        self._connector = connector
-        self._connector_owner = connector_owner
-        self._default_auth = auth
-        self._version = version
-        self._json_serialize = json_serialize
         if timeout is sentinel or timeout is None:
             self._timeout = DEFAULT_TIMEOUT
             if read_timeout is not sentinel:
@@ -324,6 +305,30 @@ def __init__(
                     "conflict, please setup "
                     "timeout.connect"
                 )
+
+        if connector is None:
+            connector = TCPConnector(loop=loop)
+
+        if connector._loop is not loop:
+            raise RuntimeError("Session and connector has to use same event loop")
+
+        self._loop = loop
+
+        if loop.get_debug():
+            self._source_traceback = traceback.extract_stack(sys._getframe(1))
+
+        if cookie_jar is None:
+            cookie_jar = CookieJar(loop=loop)
+        self._cookie_jar = cookie_jar
+
+        if cookies is not None:
+            self._cookie_jar.update_cookies(cookies)
+
+        self._connector = connector
+        self._connector_owner = connector_owner
+        self._default_auth = auth
+        self._version = version
+        self._json_serialize = json_serialize
         self._raise_for_status = raise_for_status
         self._auto_decompress = auto_decompress
         self._trust_env = trust_env
diff --git a/tests/test_client_session.py b/tests/test_client_session.py
index a0654ed8ccd..416b6bbce5d 100644
--- a/tests/test_client_session.py
+++ b/tests/test_client_session.py
@@ -885,3 +885,13 @@ async def test_build_url_returns_expected_url(
 ) -> None:
     session = await create_session(base_url)
     assert session._build_url(url) == expected_url
+
+
+async def test_instantiation_with_invalid_timeout_value(loop):
+    loop.set_debug(False)
+    logs = []
+    loop.set_exception_handler(lambda loop, ctx: logs.append(ctx))
+    with pytest.raises(ValueError, match="timeout parameter cannot be .*"):
+        ClientSession(timeout=1)
+    # should not have "Unclosed client session" warning
+    assert not logs