Fix bug with async_lock implementation

- ``async_lock`` would hold onto the lock even if a task had been cancelled. This change ensures that the lock will be released if an exception is thrown during ``loop.run_in_executor()``.

newsfragments/2695.bugfix.rst

@@ -0,0 +1 @@
+Properly release ``async_lock`` for session requests if an exception is raised during a task.

tests/core/utilities/test_request.py

@@ -29,6 +29,8 @@
 )
 from web3._utils.request import (
     SessionCache,
+    _async_session_cache_lock,
+    async_lock,
     cache_and_return_async_session,
     cache_and_return_session,
 )
@@ -323,3 +325,23 @@ def target_function(endpoint_uri):
 
     # clear cache
     request._async_session_cache.clear()
+
+
+@pytest.mark.asyncio
+async def test_async_lock_releases_if_a_task_is_cancelled():
+    # inspired by issue #2693
+    # Note: this test will raise a `TimeoutError` if `requests.async_lock` is not
+    # applied correctly
+
+    async def _utilize_async_lock():
+        async with async_lock(_async_session_cache_lock):
+            await asyncio.sleep(0.1)
+
+    asyncio.create_task(_utilize_async_lock())
+
+    inner = asyncio.create_task(_utilize_async_lock())
+    await asyncio.sleep(0.1)
+    inner.cancel()
+
+    outer = asyncio.wait_for(_utilize_async_lock(), 1)
+    await outer

web3/_utils/request.py

@@ -196,8 +196,8 @@ async def cache_and_return_async_session(
 @contextlib.asynccontextmanager
 async def async_lock(lock: threading.Lock) -> AsyncGenerator[None, None]:
     loop = asyncio.get_event_loop()
-    await loop.run_in_executor(_pool, lock.acquire)
     try:
+        await loop.run_in_executor(_pool, lock.acquire)
         yield
     finally:
         lock.release()