nest routers` lifespans

fastapi/routing.py

@@ -3,9 +3,10 @@ import dataclasses
 import email.message
 import inspect
 import json
-from contextlib import AsyncExitStack
+from contextlib import AsyncExitStack, asynccontextmanager
 from enum import Enum, IntEnum
 from typing import (
+    AsyncIterator,
     Any,
     Callable,
     Coroutine,
@@ -17,6 +18,7 @@ from typing import (
     Tuple,
     Type,
     Union,
+    Mapping,
 )
 
 from fastapi import params
@@ -57,7 +59,7 @@ from starlette.routing import (
     websocket_session,
 )
 from starlette.status import WS_1008_POLICY_VIOLATION
-from starlette.types import ASGIApp, Lifespan, Scope
+from starlette.types import ASGIApp, Lifespan, Scope, AppType
 from starlette.websockets import WebSocket
 
 
@@ -107,6 +109,21 @@ def _prepare_response_content(
     return res
 
 
+def _merge_lifespan_context(
+    original_context: Lifespan[Any], nested_context: Lifespan[Any]
+) -> Lifespan[Any]:
+    @asynccontextmanager
+    async def merged_lifespan(app: AppType) -> AsyncIterator[Mapping[str, Any]]:
+        async with original_context(app) as maybe_self_context:
+            async with nested_context(app) as maybe_nested_context:
+                context = maybe_self_context or {}
+                if maybe_nested_context:
+                    context.update(maybe_nested_context)
+                yield context
+
+    return merged_lifespan
+
+
 async def serialize_response(
     *,
     field: Optional[ModelField] = None,
@@ -830,6 +847,10 @@ class APIRouter(routing.Router):
             self.add_event_handler("startup", handler)
         for handler in router.on_shutdown:
             self.add_event_handler("shutdown", handler)
+        self.lifespan_context = _merge_lifespan_context(
+            self.lifespan_context,
+            router.lifespan_context,
+        )
 
     def get(
         self,

tests/test_router_events.py

@@ -106,3 +106,60 @@ def test_app_lifespan_state(state: State) -> None:
         assert response.json() == {"message": "Hello World"}
     assert state.app_startup is True
     assert state.app_shutdown is True
+
+
+def test_router_nested_lifespan_state(state: State) -> None:
+    @asynccontextmanager
+    async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
+        state.app_startup = True
+        yield
+        state.app_shutdown = True
+
+    @asynccontextmanager
+    async def router_lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
+        state.router_startup = True
+        yield
+        state.router_shutdown = True
+    
+    @asynccontextmanager
+    async def subrouter_lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
+        state.sub_router_startup = True
+        yield
+        state.sub_router_shutdown = True
+
+    sub_router = APIRouter(lifespan=subrouter_lifespan)
+
+    router = APIRouter(lifespan=router_lifespan)
+    router.include_router(sub_router)
+
+    app = FastAPI(lifespan=lifespan)
+    app.include_router(router)
+
+    @app.get("/")
+    def main() -> Dict[str, str]:
+        return {"message": "Hello World"}
+
+    assert state.app_startup is False
+    assert state.router_startup is False
+    assert state.sub_router_startup is False
+    assert state.app_shutdown is False
+    assert state.router_shutdown is False
+    assert state.sub_router_shutdown is False
+
+    with TestClient(app) as client:
+        assert state.app_startup is True
+        assert state.router_startup is True
+        assert state.sub_router_startup is True
+        assert state.app_shutdown is False
+        assert state.router_shutdown is False
+        assert state.sub_router_shutdown is False
+        response = client.get("/")
+        assert response.status_code == 200, response.text
+        assert response.json() == {"message": "Hello World"}
+
+    assert state.app_startup is True
+    assert state.router_startup is True
+    assert state.sub_router_startup is True
+    assert state.app_shutdown is True
+    assert state.router_shutdown is True
+    assert state.sub_router_shutdown is True