From 5f5729d2db02c5643e2e4e33d840b623a1af9c48 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Sun, 24 Nov 2024 10:35:16 -0800
Subject: [PATCH] Defer creation of cookies for client responses until needed
 (#10029)

---
 CHANGES/10029.misc.rst        |  1 +
 aiohttp/client.py             |  2 +-
 aiohttp/client_reqrep.py      | 25 +++++++++++++++++++------
 tests/test_client_response.py | 19 +++++++++++++++++++
 4 files changed, 40 insertions(+), 7 deletions(-)
 create mode 100644 CHANGES/10029.misc.rst

diff --git a/CHANGES/10029.misc.rst b/CHANGES/10029.misc.rst
new file mode 100644
index 00000000000..d98729ecac8
--- /dev/null
+++ b/CHANGES/10029.misc.rst
@@ -0,0 +1 @@
+Improved performance of creating :class:`aiohttp.ClientResponse` objects when there are no cookies -- by :user:`bdraco`.
diff --git a/aiohttp/client.py b/aiohttp/client.py
index 1485356c3a1..16c8c749ea0 100644
--- a/aiohttp/client.py
+++ b/aiohttp/client.py
@@ -687,7 +687,7 @@ async def _request(
                             raise
                         raise ClientOSError(*exc.args) from exc
 
-                    if cookies := resp.cookies:
+                    if cookies := resp._cookies:
                         self._cookie_jar.update_cookies(cookies, resp.url)
 
                     # redirects
diff --git a/aiohttp/client_reqrep.py b/aiohttp/client_reqrep.py
index 1ca93a2bf7a..08a4d44b345 100644
--- a/aiohttp/client_reqrep.py
+++ b/aiohttp/client_reqrep.py
@@ -766,6 +766,7 @@ class ClientResponse(HeadersMixin):
     _raw_headers: RawHeaders = None  # type: ignore[assignment]
 
     _connection: Optional["Connection"] = None  # current connection
+    _cookies: Optional[SimpleCookie] = None
     _continue: Optional["asyncio.Future[bool]"] = None
     _source_traceback: Optional[traceback.StackSummary] = None
     _session: Optional["ClientSession"] = None
@@ -797,7 +798,6 @@ def __init__(
         super().__init__()
 
         self.method = method
-        self.cookies = SimpleCookie()
 
         self._real_url = url
         self._url = url.with_fragment(None) if url.raw_fragment else url
@@ -846,6 +846,16 @@ def _writer(self, writer: Optional["asyncio.Task[None]"]) -> None:
         else:
             writer.add_done_callback(self.__reset_writer)
 
+    @property
+    def cookies(self) -> SimpleCookie:
+        if self._cookies is None:
+            self._cookies = SimpleCookie()
+        return self._cookies
+
+    @cookies.setter
+    def cookies(self, cookies: SimpleCookie) -> None:
+        self._cookies = cookies
+
     @reify
     def url(self) -> URL:
         return self._url
@@ -1005,11 +1015,14 @@ async def start(self, connection: "Connection") -> "ClientResponse":
         self.content = payload
 
         # cookies
-        for hdr in self.headers.getall(hdrs.SET_COOKIE, ()):
-            try:
-                self.cookies.load(hdr)
-            except CookieError as exc:
-                client_logger.warning("Can not load response cookies: %s", exc)
+        if cookie_hdrs := self.headers.getall(hdrs.SET_COOKIE, ()):
+            cookies = SimpleCookie()
+            for hdr in cookie_hdrs:
+                try:
+                    cookies.load(hdr)
+                except CookieError as exc:
+                    client_logger.warning("Can not load response cookies: %s", exc)
+            self._cookies = cookies
         return self
 
     def _response_eof(self) -> None:
diff --git a/tests/test_client_response.py b/tests/test_client_response.py
index 4ac96de2608..75d3ee0d4b3 100644
--- a/tests/test_client_response.py
+++ b/tests/test_client_response.py
@@ -1179,6 +1179,25 @@ def side_effect(*args: object, **kwargs: object) -> "asyncio.Future[bytes]":
     )
 
 
+def test_response_cookies(
+    loop: asyncio.AbstractEventLoop, session: ClientSession
+) -> None:
+    response = ClientResponse(
+        "get",
+        URL("http://python.org"),
+        request_info=mock.Mock(),
+        writer=WriterMock(),
+        continue100=None,
+        timer=TimerNoop(),
+        traces=[],
+        loop=loop,
+        session=session,
+    )
+    cookies = response.cookies
+    # Ensure the same cookies object is returned each time
+    assert response.cookies is cookies
+
+
 def test_response_real_url(
     loop: asyncio.AbstractEventLoop, session: ClientSession
 ) -> None: