Drain completed future exceptions for invalid callback returns

Co-authored-by: Shri Sukhani <shrisukhani@users.noreply.github.com>

Author: cursoragent

hyperbrowser/client/polling.py

@@ -93,8 +93,16 @@ def _ensure_non_awaitable(
     if inspect.isawaitable(result):
         if inspect.iscoroutine(result):
             result.close()
-        elif isinstance(result, asyncio.Future) and not result.done():
-            result.cancel()
+        elif isinstance(result, asyncio.Future):
+            if result.done():
+                try:
+                    result.exception()
+                except asyncio.CancelledError:
+                    pass
+                except Exception:
+                    pass
+            else:
+                result.cancel()
         raise _NonRetryablePollingError(
             f"{callback_name} must return a non-awaitable result for {operation_name}"
         )

tests/test_polling.py

@@ -654,6 +654,27 @@ def test_retry_operation_cancels_future_operation_results():
         loop.close()
 
 
+def test_retry_operation_consumes_completed_future_exceptions():
+    loop = asyncio.new_event_loop()
+    try:
+        completed_future = loop.create_future()
+        completed_future.set_exception(RuntimeError("boom"))
+
+        with pytest.raises(
+            HyperbrowserError, match="operation must return a non-awaitable result"
+        ):
+            retry_operation(
+                operation_name="sync retry completed-future callback",
+                operation=lambda: completed_future,  # type: ignore[return-value]
+                max_attempts=5,
+                retry_delay_seconds=0.0001,
+            )
+
+        assert getattr(completed_future, "_log_traceback", False) is False
+    finally:
+        loop.close()
+
+
 def test_async_polling_and_retry_helpers():
     async def run() -> None:
         status_values = iter(["pending", "completed"])