[Reginald Alfret V (reginaldalfret)]

Fixes #3266

Summary

In playwright/_impl/_connection.py, _done_callback was calling future.exception() unconditionally. In Python asyncio, calling .exception() on a cancelled future raises asyncio.CancelledError. When exiting sync_playwright() with pending tasks (such as an unanswered route handler), cancelling the task caused an unhandled CancelledError to be logged from the event loop callback.

Changes

• In Connection.dispatch, guarded _done_callback with if future.cancelled(): return prior to inspecting future.exception().
• Added unit test test_sync_event_listener_cancelled_future in tests/sync/test_sync.py verifying that cancelled futures attached to event listeners do not raise unhandled errors.