Allow route decorators to stack up again (#1764)

* Allow route decorators to stack up without causing a function signature inspection crash
Fix #1742

* Apply fix to @websocket routes docorator too
Add test for double-stacked websocket decorator
remove introduction of new variable in route wrapper, extend routes in-place.
Add explanation of why a handler will be a tuple in the case of a double-stacked route decorator

tests/test_routes.py

@@ -551,6 +551,35 @@ def test_route_duplicate(app):
             pass
 
 
+def test_double_stack_route(app):
+    @app.route("/test/1")
+    @app.route("/test/2")
+    async def handler1(request):
+        return text("OK")
+
+    request, response = app.test_client.get("/test/1")
+    assert response.status == 200
+    request, response = app.test_client.get("/test/2")
+    assert response.status == 200
+
+
+@pytest.mark.asyncio
+async def test_websocket_route_asgi(app):
+    ev = asyncio.Event()
+
+    @app.websocket("/test/1")
+    @app.websocket("/test/2")
+    async def handler(request, ws):
+        ev.set()
+
+    request, response = await app.asgi_client.websocket("/test/1")
+    first_set = ev.is_set()
+    ev.clear()
+    request, response = await app.asgi_client.websocket("/test/1")
+    second_set = ev.is_set()
+    assert(first_set and second_set)
+
+
 def test_method_not_allowed(app):
     @app.route("/test", methods=["GET"])
     async def handler(request):