Let companion ASGI app handle lifespan events (Fixes #287)

src/engineio/async_drivers/asgi.py

@@ -60,7 +60,7 @@ async def __call__(self, scope, receive, send):
             static_file = get_static_file(scope['path'], self.static_files) \
                 if scope['type'] == 'http' and self.static_files else None
             if scope['type'] == 'lifespan':
-                await self.lifespan(receive, send)
+                await self.lifespan(scope, receive, send)
             elif static_file and os.path.exists(static_file['filename']):
                 await self.serve_static_file(static_file, receive, send)
             elif self.other_asgi_app is not None:
@@ -81,7 +81,13 @@ async def serve_static_file(self, static_file, receive,
             await send({'type': 'http.response.body',
                         'body': payload})
 
-    async def lifespan(self, receive, send):
+    async def lifespan(self, scope, receive, send):
+        if self.other_asgi_app is not None and self.on_startup is None and \
+                self.on_shutdown is None:
+            # let the other ASGI app handle lifespan events
+            await self.other_asgi_app(scope, receive, send)
+            return
+
         while True:
             event = await receive()
             if event['type'] == 'lifespan.startup':

tests/asyncio/test_async_asgi.py

@@ -54,6 +54,13 @@ def test_other_app_routing(self):
         _run(app(scope, 'receive', 'send'))
         other_app.mock.assert_called_once_with(scope, 'receive', 'send')
 
+    def test_other_app_lifespan_routing(self):
+        other_app = AsyncMock()
+        app = async_asgi.ASGIApp('eio', other_app)
+        scope = {'type': 'lifespan'}
+        _run(app(scope, 'receive', 'send'))
+        other_app.mock.assert_called_once_with(scope, 'receive', 'send')
+
     def test_static_file_routing(self):
         root_dir = os.path.dirname(__file__)
         app = async_asgi.ASGIApp(