[WIP] Adds router resolver 404 exception

channels/exceptions.py

@@ -1,3 +1,6 @@
+from django.urls import Resolver404
+
+
 class RequestAborted(Exception):
     """
     Raised when the incoming request tells us it's aborted partway through
@@ -63,3 +66,12 @@ class StopConsumer(Exception):
     """
 
     pass
+
+
+class RouterResolver404(Resolver404, ValueError):
+    """
+    Raised when a router cannot resolve a path.
+    Backwards compatible, in future ValueError will be deprecated in favor of Resolver404
+    """
+
+    pass

channels/routing.py

@@ -5,6 +5,8 @@
 from django.urls.exceptions import Resolver404
 from django.urls.resolvers import RegexPattern, RoutePattern, URLResolver
 
+from channels.exceptions import RouterResolver404
+
 """
 All Routing instances inside this file are also valid ASGI applications - with
 new Channels routing, whatever you end up with as the top level object is just
@@ -99,7 +101,7 @@ async def __call__(self, scope, receive, send):
             root_path = scope.get("root_path", "")
             if root_path and not path.startswith(root_path):
                 # If root_path is present, path must start with it.
-                raise ValueError("No route found for path %r." % path)
+                raise RouterResolver404("No route found for path %r." % path)
             path = path[len(root_path) :]
 
         # Remove leading / to match Django's handling
@@ -127,13 +129,13 @@ async def __call__(self, scope, receive, send):
                         receive,
                         send,
                     )
-            except Resolver404:
+            except RouterResolver404:
                 pass
         else:
             if "path_remaining" in scope:
-                raise Resolver404("No route found for path %r." % path)
+                raise RouterResolver404("No route found for path %r." % path)
             # We are the outermost URLRouter
-            raise ValueError("No route found for path %r." % path)
+            raise RouterResolver404("No route found for path %r." % path)
 
 
 class ChannelNameRouter:

tests/test_routing.py

@@ -2,6 +2,7 @@
 from django.core.exceptions import ImproperlyConfigured
 from django.urls import path, re_path
 
+from channels.exceptions import RouterResolver404
 from channels.routing import ChannelNameRouter, ProtocolTypeRouter, URLRouter
 
 
@@ -312,3 +313,26 @@ def test_invalid_routes():
         URLRouter([path("", include([]))])
 
     assert "include() is not supported in URLRouter." in str(exc)
+
+
+@pytest.mark.asyncio
+async def test_non_existent_route_returns_not_found():
+    """
+    Test URLRouter route validation on non existent routes
+    """
+    router = URLRouter([path("ws/existing", MockApplication(return_value=1))])
+
+    with pytest.raises(RouterResolver404):
+        await router(
+            {"type": "websocket", "path": "/", "root_path": "/"},
+            None,
+            None,
+        )
+
+    expected_result = await router(
+        {"type": "websocket", "path": "/ws/existing"},
+        None,
+        None,
+    )
+    assert expected_result == 1
+    # todo check nested routing