request.url_vars property, closes #822

docs/internals.rst

@@ -42,6 +42,9 @@ The request object is passed to various plugin hooks. It represents an incoming
 ``.args`` - MultiParams
     An object representing the parsed querystring parameters, see below.
 
+``.url_vars`` - dictionary (str -> str)
+    Variables extracted from the URL path, if that path was defined using a regular expression. See :ref:`plugin_register_routes`.
+
 ``.actor`` - dictionary (str -> Any) or None
     The currently authenticated actor (see :ref:`actors <authentication_actor>`), or ``None`` if the request is unauthenticated.
 

docs/plugins.rst

@@ -850,8 +850,8 @@ Return a list of ``(regex, async_view_function)`` pairs, something like this:
     import html
 
 
-    async def hello_from(scope):
-        name = scope["url_route"]["kwargs"]["name"]
+    async def hello_from(request):
+        name = request.url_vars["name"]
         return Response.html("Hello from {}".format(
             html.escape(name)
         ))