Fix add_task() method

Author: Cito

src/graphql/execution/execute.py

@@ -1724,7 +1724,7 @@ async def execute_stream_async_iterator(
             previous_incremental_data_record = incremental_data_record
             index += 1
 
-    async def add_task(self, awaitable: Awaitable[Any]) -> None:
+    def add_task(self, awaitable: Awaitable[Any]) -> None:
         """Add task."""
         tasks = self._tasks
         task = ensure_future(awaitable)

src/graphql/execution/incremental_publisher.py

@@ -386,7 +386,8 @@ async def subscribe(
             while not is_done:
                 released = self._released
                 for item in released:
-                    del pending[item]
+                    if item in pending:
+                        del pending[item]
                 self._released = {}
 
                 result = self._get_incremental_result(released)
@@ -592,7 +593,7 @@ def _matches_path(
     ) -> bool:
         return all(item == test_path[i] for i, item in enumerate(base_path))
 
-    async def _add_task(self, awaitable: Awaitable[Any]) -> None:
+    def _add_task(self, awaitable: Awaitable[Any]) -> None:
         tasks = self._tasks
         task = ensure_future(awaitable)
         tasks.add(task)

tests/execution/test_defer.py

@@ -742,7 +742,6 @@ async def handles_non_nullable_errors_thrown_outside_deferred_fragments():
 
     @pytest.mark.asyncio()
     async def handles_async_non_nullable_errors_thrown_in_deferred_fragments():
-        return  # TODO: hangs
         document = parse(
             """
             query HeroNameQuery {