raise exception when param conflicts in route

sanic/router.py

@@ -38,6 +38,10 @@ class RouteDoesNotExist(Exception):
     pass
 
 
+class ParameterNameConflicts(Exception):
+    pass
+
+
 class Router:
     """Router supports basic routing with parameters and method checks
 
@@ -195,12 +199,17 @@ class Router:
             methods = frozenset(methods)
 
         parameters = []
+        parameter_names = set()
         properties = {"unhashable": None}
 
         def add_parameter(match):
             name = match.group(1)
             name, _type, pattern = self.parse_parameter_string(name)
 
+            if name in parameter_names:
+                raise ParameterNameConflicts("Multiple parameter named <{name}> in route uri {uri}".format(name=name, uri=uri))
+            parameter_names.add(name)
+
             parameter = Parameter(
                 name=name, cast=_type)
             parameters.append(parameter)

tests/test_routes.py

@@ -3,7 +3,7 @@ import pytest
 
 from sanic import Sanic
 from sanic.response import text, json
-from sanic.router import RouteExists, RouteDoesNotExist
+from sanic.router import RouteExists, RouteDoesNotExist, ParameterNameConflicts
 from sanic.constants import HTTP_METHODS
 
 
@@ -935,3 +935,10 @@ def test_uri_with_different_method_and_different_params(app):
     assert response.json == {
         'action': 'post'
     }
+
+
+def test_route_raise_ParameterNameConflicts(app):
+    with pytest.raises(ParameterNameConflicts):
+        @app.get('/api/v1/<user>/<user>/')
+        def handler(request, user):
+            return text('OK')