Use asyncio.run in StatelessServer.run

asgiref/server.py

@@ -56,9 +56,8 @@ def run(self):
         """
         Runs the asyncio event loop with our handler loop.
         """
-        event_loop = asyncio.get_event_loop()
         try:
-            event_loop.run_until_complete(self.arun())
+            asyncio.run(self.arun())
         except KeyboardInterrupt:
             logger.info("Exiting due to Ctrl-C/interrupt")
 

tests/test_server.py

@@ -124,6 +124,32 @@ async def do_test():
         pass
 
 
+def test_run_creates_event_loop_when_none_exists(monkeypatch):
+    async def app(scope, receive, send):
+        pass
+
+    class RunServer(StatelessServer):
+        def __init__(self):
+            super().__init__(app)
+            self.handled = False
+
+        async def handle(self):
+            self.handled = True
+
+        async def application_send(self, scope, message):
+            pass
+
+    def raise_no_event_loop():
+        raise RuntimeError("There is no current event loop in thread 'MainThread'.")
+
+    monkeypatch.setattr(asyncio, "get_event_loop", raise_no_event_loop)
+
+    server = RunServer()
+    server.run()
+
+    assert server.handled
+
+
 @pytest.mark.asyncio
 async def test_server_delete_instance(server):
     """The max_applications of Server is 10. After 20 times register, application number should be 10."""