Add __slots__ to timer helpers (#9406)

Co-authored-by: Sam Bull <git@sambull.org>
(cherry picked from commit 24b0e6f)

CHANGES/9406.misc.rst

@@ -0,0 +1 @@
+Reduced memory required for timer objects created during the client request lifecycle -- by :user:`bdraco`.

aiohttp/helpers.py

@@ -581,6 +581,8 @@ def calculate_timeout_when(
 class TimeoutHandle:
     """Timeout handle"""
 
+    __slots__ = ("_timeout", "_loop", "_ceil_threshold", "_callbacks")
+
     def __init__(
         self,
         loop: asyncio.AbstractEventLoop,
@@ -629,11 +631,17 @@ def __call__(self) -> None:
 
 
 class BaseTimerContext(ContextManager["BaseTimerContext"]):
+
+    __slots__ = ()
+
     def assert_timeout(self) -> None:
         """Raise TimeoutError if timeout has been exceeded."""
 
 
 class TimerNoop(BaseTimerContext):
+
+    __slots__ = ()
+
     def __enter__(self) -> BaseTimerContext:
         return self
 
@@ -649,6 +657,8 @@ def __exit__(
 class TimerContext(BaseTimerContext):
     """Low resolution timeout context manager"""
 
+    __slots__ = ("_loop", "_tasks", "_cancelled", "_cancelling")
+
     def __init__(self, loop: asyncio.AbstractEventLoop) -> None:
         self._loop = loop
         self._tasks: List[asyncio.Task[Any]] = []

pyproject.toml

@@ -82,3 +82,8 @@ skip = "pp*"
 [tool.codespell]
 skip = '.git,*.pdf,*.svg,Makefile,CONTRIBUTORS.txt,venvs,_build'
 ignore-words-list = 'te'
+
+[tool.slotscheck]
+# TODO(3.13): Remove aiohttp.helpers once https://github.com/python/cpython/pull/106771
+# is available in all supported cpython versions
+exclude-modules = "(^aiohttp\\.helpers)"