From cd5261fae7c34014686d0a2b7af6078f45e64d2c Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Wed, 10 Jan 2024 14:56:51 -1000
Subject: [PATCH] Fix double compress when compression enabled and compressed
 file exists (#8014)

(cherry picked from commit 92655a50987e8bdfb6241dabbedc4c3cc8f55272)
---
 CHANGES/8014.bugfix                   |  1 +
 aiohttp/web_fileresponse.py           |  4 ++++
 tests/test_web_sendfile_functional.py | 30 ++++++++++++++++++++++++++-
 3 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100644 CHANGES/8014.bugfix

diff --git a/CHANGES/8014.bugfix b/CHANGES/8014.bugfix
new file mode 100644
index 00000000000..681bb5966ae
--- /dev/null
+++ b/CHANGES/8014.bugfix
@@ -0,0 +1 @@
+Fix double compress when compression enabled and compressed file exists
diff --git a/aiohttp/web_fileresponse.py b/aiohttp/web_fileresponse.py
index c3b3814974e..6496ffaf317 100644
--- a/aiohttp/web_fileresponse.py
+++ b/aiohttp/web_fileresponse.py
@@ -267,6 +267,10 @@ async def prepare(self, request: "BaseRequest") -> Optional[AbstractStreamWriter
             self.headers[hdrs.CONTENT_ENCODING] = encoding
         if gzip:
             self.headers[hdrs.VARY] = hdrs.ACCEPT_ENCODING
+            # Disable compression if we are already sending
+            # a compressed file since we don't want to double
+            # compress.
+            self._compression = False
 
         self.etag = etag_value  # type: ignore[assignment]
         self.last_modified = st.st_mtime  # type: ignore[assignment]
diff --git a/tests/test_web_sendfile_functional.py b/tests/test_web_sendfile_functional.py
index 3f4f13354ec..31f22892f66 100644
--- a/tests/test_web_sendfile_functional.py
+++ b/tests/test_web_sendfile_functional.py
@@ -250,7 +250,35 @@ async def handler(request):
     await client.close()
 
 
-async def test_static_file_with_content_encoding(aiohttp_client, sender) -> None:
+async def test_static_file_with_gziped_counter_part_enable_compression(
+    aiohttp_client: Any, sender: Any
+):
+    """Test that enable_compression does not double compress when a .gz file is also present."""
+    filepath = pathlib.Path(__file__).parent / "hello.txt"
+
+    async def handler(request):
+        resp = sender(filepath)
+        resp.enable_compression()
+        return resp
+
+    app = web.Application()
+    app.router.add_get("/", handler)
+    client = await aiohttp_client(app)
+
+    resp = await client.get("/")
+    assert resp.status == 200
+    body = await resp.read()
+    assert body == b"hello aiohttp\n"
+    assert resp.headers["Content-Type"] == "text/plain"
+    assert resp.headers.get("Content-Encoding") == "gzip"
+    resp.close()
+    await resp.release()
+    await client.close()
+
+
+async def test_static_file_with_content_encoding(
+    aiohttp_client: Any, sender: Any
+) -> None:
     filepath = pathlib.Path(__file__).parent / "hello.txt.gz"
 
     async def handler(request):