Support the older Python versions

src/graphql/execution/incremental_publisher.py

@@ -364,12 +364,13 @@ class IncrementalPublisher:
     _initial_result: InitialResult
     _released: dict[IncrementalDataRecord, None]
     _pending: dict[IncrementalDataRecord, None]
+    _resolve: Event | None
 
     def __init__(self) -> None:
         self._initial_result = InitialResult({}, False)
         self._released = {}
         self._pending = {}
-        self._resolve = Event()
+        self._resolve = None  # lazy initialization
         self._tasks: set[Awaitable] = set()
 
     def has_next(self) -> bool:
@@ -399,7 +400,10 @@ async def subscribe(
                 if result is not None:
                     yield result
                 else:
-                    await self._resolve.wait()
+                    resolve = self._resolve
+                    if resolve is None:
+                        self._resolve = resolve = Event()
+                    await resolve.wait()
         finally:
             close_async_iterators = []
             for incremental_data_record in pending:
@@ -511,7 +515,9 @@ def filter(
 
     def _trigger(self) -> None:
         """Trigger the resolve event."""
-        self._resolve.set()
+        resolve = self._resolve
+        if resolve is not None:
+            resolve.set()
         self._resolve = Event()
 
     def _introduce(self, item: IncrementalDataRecord) -> None:

tests/execution/test_stream.py

@@ -1387,7 +1387,7 @@ async def get_friend(i):
             return {"nonNullName": throw() if i < 0 else friends[i].name}
 
         async def get_friends(_info):
-            for i in 0, -1, 1:
+            for i in 0, -1, 1:  # pragma: no cover exit
                 yield await get_friend(i)
 
         result = await complete(