improve URL matching algorithm in case of ambiguity

starlette/routing.py

@@ -724,19 +724,45 @@ async def app(self, scope: Scope, receive: Receive, send: Send) -> None:
             return
 
         partial = None
+        full_match_route = None
+        full_match_best_number_of_path_params = None
 
         for route in self.routes:
             # Determine if any route matches the incoming scope,
             # and hand over to the matching route if found.
             match, child_scope = route.matches(scope)
             if match == Match.FULL:
-                scope.update(child_scope)
-                await route.handle(scope, receive, send)
-                return
+                number_of_path_params = len(child_scope["path_params"])
+                if number_of_path_params == 0:
+                    scope.update(child_scope)
+                    await route.handle(scope, receive, send)
+                    return
+                # in case we have 2 routes that fully match the requested URL
+                # we need to check which one is a stricter match.
+                # Example:
+                # we have 2 endpoints:
+                # /user/{user_id}
+                # /user/myself
+                # if the requested URL is /user/myself, then both endpoints are
+                # a full match, however the last one is a more appropriate choice
+                # in case of ambiguity
+                if full_match_route is None or (
+                    full_match_best_number_of_path_params is not None
+                    and number_of_path_params < full_match_best_number_of_path_params
+                ):
+                    full_match_route = route
+                    full_match_scope = child_scope
+                    full_match_best_number_of_path_params = number_of_path_params
+
             elif match == Match.PARTIAL and partial is None:
                 partial = route
                 partial_scope = child_scope
 
+        if full_match_route is not None:
+            scope.update(full_match_scope)
+            await full_match_route.handle(scope, receive, send)
+            return
+
         if partial is not None:
             #  Handle partial matches. These are cases where an endpoint is
             # able to handle the request, but is not a preferred option.

tests/test_routing.py

@@ -33,6 +33,16 @@ def user(request: Request) -> Response:
     return Response(content, media_type="text/plain")
 
 
+def user_greet(request: Request) -> Response:
+    content = "User " + request.path_params["username"] + " greeted"
+    return Response(content, media_type="text/plain")
+
+
+def user_action(request: Request) -> Response:
+    content = "User " + request.path_params["username"] + " action " + request.path_params["action"]
+    return Response(content, media_type="text/plain")
+
+
 def user_me(request: Request) -> Response:
     content = "User fixed me"
     return Response(content, media_type="text/plain")
@@ -124,6 +134,8 @@ async def websocket_params(session: WebSocket) -> None:
                 Route("/", endpoint=users),
                 Route("/me", endpoint=user_me),
                 Route("/{username}", endpoint=user),
+                Route("/{username}/greet", endpoint=user_greet),
+                Route("/{username}/{action}", endpoint=user_action),
                 Route("/{username}:disable", endpoint=disable_user, methods=["PUT"]),
                 Route("/nomatch", endpoint=user_no_match),
             ],
@@ -212,9 +224,21 @@ def test_router(client: TestClient) -> None:
     assert response.url == "http://testserver/users/tomchristie:disable"
     assert response.text == "User tomchristie disabled"
 
+    response = client.get("/users/notmatch")
+    assert response.status_code == 200
+    assert response.text == "User notmatch"
+
     response = client.get("/users/nomatch")
     assert response.status_code == 200
-    assert response.text == "User nomatch"
+    assert response.text == "User fixed no match"
+
+    response = client.get("/users/nomatch/greet")
+    assert response.status_code == 200
+    assert response.text == "User nomatch greeted"
+
+    response = client.get("/users/nomatch/complimented")
+    assert response.status_code == 200
+    assert response.text == "User nomatch action complimented"
 
     response = client.get("/static/123")
     assert response.status_code == 200