If a task gets canceled while holding a lock, the lock is not automatically released. Is that expected, it seems like it could cause a deadlock?

Failing test adapted from Lib/test/test_asyncio/test_locks.py (commit 6bd9288b80):

    def test_acquire_cancel(self):
        lock = asyncio.Lock()
        self.assertTrue(self.loop.run_until_complete(lock.acquire()))

        task = self.loop.create_task(lock.acquire())
        self.loop.call_soon(task.cancel)
        self.assertRaises(
            asyncio.CancelledError,
            self.loop.run_until_complete, task)
        self.assertFalse(lock._waiters)

        # Should the lock get released after cancellation?
        self.assertFalse(lock.locked())

I stumbled upon this while playing around with TLA+.

a.niederbuehl tasks are free of context, meaning that the task does not know what was done inside it, and by consequence is impossible to know when or not release a lock. This is by design and normally in these cases you need to be aware of the lock, by for example checking if the lock was released before cancelling the task.

That makes sense, thanks!