Fix #1743: scene handling for channel updates (#1763)

* Fix scene handling for channel updates with missing FSM state (#1743)

* Add changelog entry for scene handling fix

* Refine scene context error handling

tests/test_fsm/test_middleware.py

@@ -0,0 +1,90 @@
+from aiogram.fsm.middleware import FSMContextMiddleware
+from aiogram.fsm.storage.memory import DisabledEventIsolation, MemoryStorage
+from aiogram.fsm.strategy import FSMStrategy
+from tests.mocked_bot import MockedBot
+
+CHANNEL_ID = -1001234567890
+THREAD_ID = 42
+
+
+def create_middleware(strategy: FSMStrategy) -> FSMContextMiddleware:
+    return FSMContextMiddleware(
+        storage=MemoryStorage(),
+        events_isolation=DisabledEventIsolation(),
+        strategy=strategy,
+    )
+
+
+class TestFSMContextMiddleware:
+    def test_resolve_context_for_channel_in_chat_strategy(self):
+        bot = MockedBot()
+        middleware = create_middleware(FSMStrategy.CHAT)
+
+        context = middleware.resolve_context(
+            bot=bot,
+            chat_id=CHANNEL_ID,
+            user_id=None,
+        )
+
+        assert context is not None
+        assert context.key.chat_id == CHANNEL_ID
+        assert context.key.user_id == CHANNEL_ID
+
+    def test_resolve_context_with_missing_user_in_chat_topic_strategy_uses_chat_id_for_user_id(
+        self,
+    ):
+        """
+        When user_id is absent (e.g., channel-like updates), chat-scoped strategies
+        should still build a stable FSM key by mirroring chat_id into user_id.
+        """
+        bot = MockedBot()
+        middleware = create_middleware(FSMStrategy.CHAT_TOPIC)
+
+        context = middleware.resolve_context(
+            bot=bot,
+            chat_id=CHANNEL_ID,
+            user_id=None,
+            thread_id=THREAD_ID,
+        )
+
+        assert context is not None
+        assert context.key.chat_id == CHANNEL_ID
+        assert context.key.user_id == CHANNEL_ID
+        assert context.key.thread_id == THREAD_ID
+
+    def test_resolve_context_for_channel_in_user_in_chat_strategy(self):
+        bot = MockedBot()
+        middleware = create_middleware(FSMStrategy.USER_IN_CHAT)
+
+        context = middleware.resolve_context(
+            bot=bot,
+            chat_id=CHANNEL_ID,
+            user_id=None,
+        )
+
+        assert context is None
+
+    def test_resolve_context_for_channel_in_global_user_strategy(self):
+        bot = MockedBot()
+        middleware = create_middleware(FSMStrategy.GLOBAL_USER)
+
+        context = middleware.resolve_context(
+            bot=bot,
+            chat_id=CHANNEL_ID,
+            user_id=None,
+        )
+
+        assert context is None
+
+    def test_resolve_context_for_channel_in_user_in_topic_strategy(self):
+        bot = MockedBot()
+        middleware = create_middleware(FSMStrategy.USER_IN_TOPIC)
+
+        context = middleware.resolve_context(
+            bot=bot,
+            chat_id=CHANNEL_ID,
+            user_id=None,
+            thread_id=THREAD_ID,
+        )
+
+        assert context is None

tests/test_fsm/test_scene.py

@@ -309,6 +309,34 @@ class TestSceneHandlerWrapper:
             # Check whether result is correct
             assert result == 42
 
+    async def test_scene_handler_wrapper_call_without_scene_context(self):
+        class MyScene(Scene):
+            pass
+
+        async def handler_mock(*args, **kwargs):
+            return 42
+
+        event_update_mock = Update(
+            update_id=42,
+            message=Message(
+                message_id=42,
+                text="test",
+                date=datetime.now(),
+                chat=Chat(
+                    type="private",
+                    id=42,
+                ),
+            ),
+        )
+
+        scene_handler_wrapper = SceneHandlerWrapper(MyScene, handler_mock)
+
+        with pytest.raises(
+            SceneException,
+            match="Scene context key 'state' is not available. Ensure FSM is enabled and pipeline is intact.",
+        ):
+            await scene_handler_wrapper(event_update_mock, event_update=event_update_mock)
+
     def test_scene_handler_wrapper_str(self):
         class MyScene(Scene):
             pass
@@ -1558,6 +1586,27 @@ class TestSceneRegistry:
         handler.assert_called_once_with(event, data)
         assert result == handler.return_value
 
+    async def test_scene_registry_update_middleware_without_state(self):
+        router = Router()
+        registry = SceneRegistry(router)
+        handler = AsyncMock(spec=NextMiddlewareType)
+        event = Update(
+            update_id=42,
+            message=Message(
+                message_id=42,
+                text="test",
+                date=datetime.now(),
+                chat=Chat(id=42, type="private"),
+            ),
+        )
+        data = {}
+
+        result = await registry._update_middleware(handler, event, data)
+
+        assert "scenes" not in data
+        handler.assert_called_once_with(event, data)
+        assert result == handler.return_value
+
     async def test_scene_registry_update_middleware_not_update(self, bot: MockedBot):
         router = Router()
         registry = SceneRegistry(router)
@@ -1604,6 +1653,24 @@ class TestSceneRegistry:
         handler.assert_called_once_with(event, data)
         assert result == handler.return_value
 
+    async def test_scene_registry_middleware_without_state(self):
+        router = Router()
+        registry = SceneRegistry(router)
+        handler = AsyncMock(spec=NextMiddlewareType)
+        event = Message(
+            message_id=42,
+            text="test",
+            date=datetime.now(),
+            chat=Chat(id=42, type="private"),
+        )
+        data = {}
+
+        result = await registry._middleware(handler, event, data)
+
+        assert "scenes" not in data
+        handler.assert_called_once_with(event, data)
+        assert result == handler.return_value
+
 
 class TestSceneInheritance:
     def test_inherit_handlers(self):