[PR #9745/0d10447 backport][3.11] Speed up preparing headers by avoiding populating cookies when there are no cookies (#9749)

Co-authored-by: Emmanuel Okedele <[email protected]>
Co-authored-by: pre-commit-ci[bot]
Co-authored-by: J. Nick Koston <[email protected]>
Co-authored-by: Emmanuel Okedele <[email protected]>

Author: bdraco

aiohttp/web_response.py

@@ -465,9 +465,10 @@ async def _prepare_headers(self) -> None:
         version = request.version
 
         headers = self._headers
-        for cookie in self._cookies.values():
-            value = cookie.output(header="")[1:]
-            headers.add(hdrs.SET_COOKIE, value)
+        if self._cookies:
+            for cookie in self._cookies.values():
+                value = cookie.output(header="")[1:]
+                headers.add(hdrs.SET_COOKIE, value)
 
         if self._compression:
             await self._start_compression(request)
@@ -515,9 +516,8 @@ async def _prepare_headers(self) -> None:
             if keep_alive:
                 if version == HttpVersion10:
                     headers[hdrs.CONNECTION] = "keep-alive"
-            else:
-                if version == HttpVersion11:
-                    headers[hdrs.CONNECTION] = "close"
+            elif version == HttpVersion11:
+                headers[hdrs.CONNECTION] = "close"
 
     async def _write_headers(self) -> None:
         request = self._req

tests/test_imports.py

@@ -49,6 +49,7 @@ def test_web___all__(pytester: pytest.Pytester) -> None:
     not sys.platform.startswith("linux") or platform.python_implementation() == "PyPy",
     reason="Timing is more reliable on Linux",
 )
+@pytest.mark.dev_mode
 def test_import_time(pytester: pytest.Pytester) -> None:
     """Check that importing aiohttp doesn't take too long.