fix: handle task cancellation in pool acquire() to prevent leaks

Changed except Exception to except BaseException so that
asyncio.CancelledError (a BaseException since Python 3.9) properly
closes the connection and decrements the pool size counter. Previously,
cancelled tasks leaked their connections permanently.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/dqliteclient/pool.py

@@ -82,11 +82,11 @@ async def acquire(self) -> AsyncIterator[DqliteConnection]:
                 await conn.connect()
 
             yield conn
-        except Exception:
-            # On error, close connection and create new one
+        except BaseException:
+            # On error (including cancellation), close connection
             import contextlib
 
-            with contextlib.suppress(Exception):
+            with contextlib.suppress(BaseException):
                 await conn.close()
             self._size -= 1
             raise

tests/test_pool.py

@@ -33,6 +33,40 @@ async def test_acquire_when_closed(self) -> None:
                 pass
 
 
+    async def test_cancellation_does_not_leak_connection(self) -> None:
+        """Cancelling a task that holds a connection should clean it up."""
+        import asyncio
+
+        pool = ConnectionPool(["localhost:9001"], max_size=1)
+
+        mock_conn = MagicMock()
+        mock_conn.is_connected = True
+        mock_conn.connect = AsyncMock()
+        mock_conn.close = AsyncMock()
+
+        with patch.object(pool._cluster, "connect", return_value=mock_conn):
+            await pool.initialize()
+
+        initial_size = pool._size
+
+        async def hold_connection():
+            async with pool.acquire() as conn:
+                await asyncio.sleep(10)  # Hold forever
+
+        task = asyncio.create_task(hold_connection())
+        await asyncio.sleep(0.01)  # Let task acquire
+
+        task.cancel()
+        try:
+            await task
+        except asyncio.CancelledError:
+            pass
+
+        # Connection should have been closed, size decremented
+        mock_conn.close.assert_called()
+        assert pool._size < initial_size
+
+
 class TestConnectionPoolIntegration:
     """Integration tests requiring mocked connections."""