Fix TimerContext not uncancelling the current task

[bdraco]

What do these changes do?

Fix TimerContext not uncancelling the current task

This is effectively the same fix as aio-libs/async-timeout#363 to fix cancellation leaking upwards on timeout

This is a long standing issue which will be much more obvious in 3.13 after python/cpython#117407 combined with aiohappyeyeballs 2.4.2, however it likely results in some unexplained cancellation behavior with 3.11/3.12 as well.

fixes #9325

Are there changes in behavior for the user?

cancellation will not leak upward on timeout

Is it a substantial burden for the maintainers to support this?

no

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.56%. Comparing base (8850a2d) to head (f5cbb22).
Report is 2 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #9326   +/-   ##
=======================================
  Coverage   98.56%   98.56%           
=======================================
  Files         107      107           
  Lines       34896    34939   +43     
  Branches     4135     4145   +10     
=======================================
+ Hits        34395    34438   +43     
  Misses        334      334           
  Partials      167      167           

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[bdraco]

This is probably causing a lot of unexplained behavior. I guess we should do another release.

[bdraco]

We don't handle subclassed CancelledError but cpython does via python/cpython#113848

I'm not sure that can ever happen for us though

[bdraco]

We also could swallow cancellation so we needed a similar change to python/cpython#102815

[patchback]

Backport to 3.10: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply fe26ae2 on top of patchback/backports/3.10/fe26ae2cad87b412c0372db0aaf2f3651d5d1319/pr-9326

Backporting merged PR #9326 into master

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git remote add upstream https://github.com/aio-libs/aiohttp.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.10/fe26ae2cad87b412c0372db0aaf2f3651d5d1319/pr-9326 upstream/3.10

4. Now, cherry-pick PR Fix TimerContext not uncancelling the current task #9326 contents into that branch:

   $ git cherry-pick -x fe26ae2cad87b412c0372db0aaf2f3651d5d1319

   If it'll yell at you with something like fatal: Commit fe26ae2cad87b412c0372db0aaf2f3651d5d1319 is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x fe26ae2cad87b412c0372db0aaf2f3651d5d1319

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Fix TimerContext not uncancelling the current task #9326 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.10/fe26ae2cad87b412c0372db0aaf2f3651d5d1319/pr-9326

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.

[patchback]

Backport to 3.11: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply fe26ae2 on top of patchback/backports/3.11/fe26ae2cad87b412c0372db0aaf2f3651d5d1319/pr-9326

Backporting merged PR #9326 into master

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git remote add upstream https://github.com/aio-libs/aiohttp.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.11/fe26ae2cad87b412c0372db0aaf2f3651d5d1319/pr-9326 upstream/3.11

4. Now, cherry-pick PR Fix TimerContext not uncancelling the current task #9326 contents into that branch:

   $ git cherry-pick -x fe26ae2cad87b412c0372db0aaf2f3651d5d1319

   If it'll yell at you with something like fatal: Commit fe26ae2cad87b412c0372db0aaf2f3651d5d1319 is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x fe26ae2cad87b412c0372db0aaf2f3651d5d1319

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Fix TimerContext not uncancelling the current task #9326 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.11/fe26ae2cad87b412c0372db0aaf2f3651d5d1319/pr-9326

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.

[bdraco]

Since python/cpython#117407 is going out in cpython 3.13 on Tuesday according to PEP 0179 it seems like we need to do another release before Tuesday