fix(app): pass Reflex app instance to lifespan task app parameter (#6358)

* Pass Reflex app instance to lifespan tasks

# Conflicts:
#	tests/units/app_mixins/test_lifespan.py

* test(lifespan): cover starlette_app injection paths

# Conflicts:
#	tests/units/app_mixins/test_lifespan.py

* style(lifespan): apply ruff formatting for pre-commit

* refactor(test): use LifespanMixin directly instead of DummyApp subclass

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: BABTUNA

docs/utility_methods/lifespan_tasks.md

@@ -40,8 +40,11 @@ async def long_running_task(foo, bar):
 To register a lifespan task, use `app.register_lifespan_task(coro_func, **kwargs)`.
 Any keyword arguments specified during registration will be passed to the task.
 
-If the task accepts the special argument, `app`, it will be passed the `Starlette`
-application instance.
+If the task accepts the special argument, `app`, it will be passed the Reflex app
+instance (`rx.App`/`LifespanMixin`).
+
+If the task accepts the special argument, `starlette_app`, it will be passed the
+underlying `Starlette` application instance.
 
 ```python
 app = rx.App()

reflex/app_mixins/lifespan.py

@@ -87,7 +87,7 @@ def get_lifespan_tasks(self) -> tuple[asyncio.Task | Callable, ...]:
         return tuple(self._lifespan_tasks)
 
     @contextlib.asynccontextmanager
-    async def _run_lifespan_tasks(self, app: Starlette):
+    async def _run_lifespan_tasks(self, starlette_app: Starlette):
         self._lifespan_tasks_started = True
         running_tasks = []
         try:
@@ -100,7 +100,9 @@ async def _run_lifespan_tasks(self, app: Starlette):
                     else:
                         signature = inspect.signature(task)
                         if "app" in signature.parameters:
-                            task = functools.partial(task, app=app)
+                            task = functools.partial(task, app=self)
+                        if "starlette_app" in signature.parameters:
+                            task = functools.partial(task, starlette_app=starlette_app)
                         t_ = task()
                         if isinstance(t_, contextlib._AsyncGeneratorContextManager):
                             await stack.enter_async_context(t_)

tests/units/app_mixins/test_lifespan.py

@@ -7,6 +7,7 @@
 
 import pytest
 from reflex_base.utils.exceptions import InvalidLifespanTaskTypeError
+from starlette.applications import Starlette
 
 from reflex.app_mixins.lifespan import LifespanMixin
 
@@ -38,6 +39,7 @@ def check_for_updates(timeout: int) -> int:
     assert registered_task() == 10
 
 
+@pytest.mark.asyncio
 async def test_register_lifespan_task_rejects_kwargs_for_asyncio_task():
     """Registering kwargs against an asyncio.Task raises a clear error."""
     mixin = LifespanMixin()
@@ -53,3 +55,70 @@ async def test_register_lifespan_task_rejects_kwargs_for_asyncio_task():
         task.cancel()
         with contextlib.suppress(asyncio.CancelledError):
             await task
+
+
+@pytest.mark.asyncio
+async def test_lifespan_task_app_param_receives_reflex_app_instance():
+    """Lifespan tasks should receive the Reflex app instance, not Starlette."""
+    mixin = LifespanMixin()
+    received: dict[str, object] = {}
+
+    def lifespan_task(app):
+        """Record the app argument injected by the lifespan runner."""
+        received["app"] = app
+
+    mixin.register_lifespan_task(lifespan_task)
+
+    async with mixin._run_lifespan_tasks(Starlette()):
+        await asyncio.sleep(0)
+
+    assert received["app"] is mixin
+
+
+@pytest.mark.asyncio
+async def test_lifespan_task_starlette_app_param_receives_starlette_instance():
+    """Lifespan tasks should receive the Starlette app when requested."""
+    mixin = LifespanMixin()
+    received: dict[str, object] = {}
+    starlette_app = Starlette()
+
+    def lifespan_task(starlette_app):
+        """Record the Starlette app argument injected by the lifespan runner.
+
+        Args:
+            starlette_app: Starlette app object injected by the lifespan runner.
+        """
+        received["starlette_app"] = starlette_app
+
+    mixin.register_lifespan_task(lifespan_task)
+
+    async with mixin._run_lifespan_tasks(starlette_app):
+        await asyncio.sleep(0)
+
+    assert received["starlette_app"] is starlette_app
+
+
+@pytest.mark.asyncio
+async def test_lifespan_task_both_app_and_starlette_app_params_are_injected():
+    """Lifespan tasks should receive both app and starlette_app when declared."""
+    mixin = LifespanMixin()
+    received: dict[str, object] = {}
+    starlette_app = Starlette()
+
+    def lifespan_task(app, starlette_app):
+        """Record both injected app objects from the lifespan runner.
+
+        Args:
+            app: Reflex app object injected by the lifespan runner.
+            starlette_app: Starlette app object injected by the lifespan runner.
+        """
+        received["app"] = app
+        received["starlette_app"] = starlette_app
+
+    mixin.register_lifespan_task(lifespan_task)
+
+    async with mixin._run_lifespan_tasks(starlette_app):
+        await asyncio.sleep(0)
+
+    assert received["app"] is mixin
+    assert received["starlette_app"] is starlette_app