From 19c847d458e60908d43dba4b8c60ab068c7dc6f5 Mon Sep 17 00:00:00 2001
From: Jakob Keller <57402305+jakob-keller@users.noreply.github.com>
Date: Sun, 17 Nov 2024 01:31:50 +0100
Subject: [PATCH] Support gzip compression in `ClientSession._ws_connect()` if
 specified by server

---
 CHANGES/9933.feature.rst |  1 +
 aiohttp/client.py        | 12 ++++++++++--
 2 files changed, 11 insertions(+), 2 deletions(-)
 create mode 100644 CHANGES/9933.feature.rst

diff --git a/CHANGES/9933.feature.rst b/CHANGES/9933.feature.rst
new file mode 100644
index 00000000000..47184438471
--- /dev/null
+++ b/CHANGES/9933.feature.rst
@@ -0,0 +1 @@
+Provided experimental support for communicating with WebSocket servers that require the `permessage-gzip` extension -- by :user:`jakob-keller`.
diff --git a/aiohttp/client.py b/aiohttp/client.py
index 70ec795164c..47a8cdd703e 100644
--- a/aiohttp/client.py
+++ b/aiohttp/client.py
@@ -9,6 +9,7 @@
 import sys
 import traceback
 import warnings
+import zlib
 from contextlib import suppress
 from types import TracebackType
 from typing import (
@@ -1005,7 +1006,9 @@ async def _ws_connect(
                 compress_hdrs = resp.headers.get(hdrs.SEC_WEBSOCKET_EXTENSIONS)
                 if compress_hdrs:
                     try:
-                        compress, notakeover = ws_ext_parse(compress_hdrs)
+                        compress, notakeover = ws_ext_parse(
+                            compress_hdrs, detect_gzip=True
+                        )
                     except WSHandshakeError as exc:
                         raise WSServerHandshakeError(
                             resp.request_info,
@@ -1036,7 +1039,12 @@ async def _ws_connect(
             transport = conn.transport
             assert transport is not None
             reader = WebSocketDataQueue(conn_proto, 2**16, loop=self._loop)
-            conn_proto.set_parser(WebSocketReader(reader, max_msg_size), reader)
+            conn_proto.set_parser(
+                WebSocketReader(
+                    reader, max_msg_size, compress=compress <= zlib.MAX_WBITS or "gzip"
+                ),
+                reader,
+            )
             writer = WebSocketWriter(
                 conn_proto,
                 transport,