ENG-8050: background event updates set final=None (#5898)

* ENG-8050: background event updates set `final=None`

When `final=None`, the frontend does not update the `event_processing` flag.

* Fix unit tests

Author: masenf

reflex/.templates/web/utils/state.js

@@ -665,7 +665,9 @@ export const connect = async (
       }
     }
     applyClientStorageDelta(client_storage, update.delta);
-    event_processing = !update.final;
+    if (update.final !== null) {
+      event_processing = !update.final;
+    }
     if (update.events) {
       queueEvents(update.events, socket, false, navigate, params);
     }

reflex/app.py

@@ -1556,11 +1556,14 @@ def all_routes(_request: Request) -> Response:
         )
 
     @contextlib.asynccontextmanager
-    async def modify_state(self, token: str) -> AsyncIterator[BaseState]:
+    async def modify_state(
+        self, token: str, background: bool = False
+    ) -> AsyncIterator[BaseState]:
         """Modify the state out of band.
 
         Args:
             token: The token to modify the state for.
+            background: Whether the modification is happening in a background task.
 
         Yields:
             The state to modify.
@@ -1581,7 +1584,10 @@ async def modify_state(self, token: str) -> AsyncIterator[BaseState]:
                 # When the state is modified reset dirty status and emit the delta to the frontend.
                 state._clean()
                 await self.event_namespace.emit_update(
-                    update=StateUpdate(delta=delta),
+                    update=StateUpdate(
+                        delta=delta,
+                        final=True if not background else None,
+                    ),
                     token=token,
                 )
 

reflex/istate/proxy.py

@@ -131,7 +131,9 @@ async def __aenter__(self) -> StateProxy:
 
         await self._self_actx_lock.acquire()
         self._self_actx_lock_holder = current_task
-        self._self_actx = self._self_app.modify_state(token=self._self_substate_token)
+        self._self_actx = self._self_app.modify_state(
+            token=self._self_substate_token, background=True
+        )
         mutable_state = await self._self_actx.__aenter__()
         super().__setattr__(
             "__wrapped__", mutable_state.get_substate(self._self_substate_path)

reflex/state.py

@@ -1780,7 +1780,7 @@ async def _as_state_update(
             return StateUpdate(
                 delta=delta,
                 events=fixed_events,
-                final=final if not handler.is_background else True,
+                final=final if not handler.is_background else None,
             )
         except Exception as ex:
             state._clean()
@@ -2714,7 +2714,7 @@ class StateUpdate:
     events: list[Event] = dataclasses.field(default_factory=list)
 
     # Whether this is the final state update for the event.
-    final: bool = True
+    final: bool | None = True
 
     def json(self) -> str:
         """Convert the state update to a JSON string.

tests/units/test_state.py

@@ -2102,7 +2102,8 @@ async def test_state_proxy(
             GrandchildState3.get_full_name(): {
                 "computed" + FIELD_MARKER: "",
             },
-        }
+        },
+        final=None,
     )
     assert mcall.kwargs["to"] == grandchild_state.router.session.session_id
 
@@ -2273,7 +2274,7 @@ async def test_background_task_no_block(mock_app: rx.App, token: str):
                         "other",
                     ],
                 }
-            }
+            },
         )
 
     # Explicit wait for background tasks
@@ -2313,7 +2314,7 @@ async def test_background_task_no_block(mock_app: rx.App, token: str):
             }
         },
         events=[],
-        final=True,
+        final=None,
     )
     for call in emit_mock.mock_calls[1:5]:  # pyright: ignore [reportAttributeAccessIssue]
         assert call.args[1] == StateUpdate(
@@ -2323,7 +2324,7 @@ async def test_background_task_no_block(mock_app: rx.App, token: str):
                 }
             },
             events=[],
-            final=True,
+            final=None,
         )
     assert emit_mock.mock_calls[-2].args[1] == StateUpdate(  # pyright: ignore [reportAttributeAccessIssue]
         delta={
@@ -2334,7 +2335,7 @@ async def test_background_task_no_block(mock_app: rx.App, token: str):
             }
         },
         events=[],
-        final=True,
+        final=None,
     )
     assert emit_mock.mock_calls[-1].args[1] == StateUpdate(  # pyright: ignore [reportAttributeAccessIssue]
         delta={
@@ -2343,7 +2344,7 @@ async def test_background_task_no_block(mock_app: rx.App, token: str):
             },
         },
         events=[],
-        final=True,
+        final=None,
     )