fix router prefix collision causing 405 errors

ninja/router.py

@@ -385,8 +385,9 @@ def urls_paths(self, prefix: str) -> Iterator[URLPattern]:
         # Ensure decorators are applied before generating URLs
         self._apply_decorators_to_operations()
 
+        all_path_operations = self._get_all_path_operations(prefix)
         prefix = replace_path_param_notation(prefix)
-        for path, path_view in self.path_operations.items():
+        for path, path_view in all_path_operations.items():
             for operation in path_view.operations:
                 path = replace_path_param_notation(path)
                 route = "/".join([i for i in (prefix, path) if i])
@@ -400,6 +401,43 @@ def urls_paths(self, prefix: str) -> Iterator[URLPattern]:
 
                 yield django_path(route, path_view.get_view(), name=url_name)
 
+    def _get_all_path_operations(self, prefix: str) -> Dict[str, Any]:
+        all_path_operations = dict(self.path_operations)
+
+        if not self.api:
+            return all_path_operations  # pragma: no cover
+
+        current_prefix_norm = normalize_path(prefix).lstrip("/")
+
+        for other_prefix, other_router in self.api._routers:
+            if other_router == self:
+                continue
+
+            other_prefix_norm = normalize_path(other_prefix).lstrip("/")
+            if other_prefix_norm != current_prefix_norm:
+                continue
+
+            # merge operations from router with same normalized prefix
+            for path, other_path_view in other_router.path_operations.items():
+                if path not in all_path_operations:
+                    all_path_operations[path] = other_path_view
+                    continue
+
+                # merge operations for same path
+                existing_methods = {
+                    m for op in all_path_operations[path].operations for m in op.methods
+                }
+                for operation in other_path_view.operations:
+                    if any(m in existing_methods for m in operation.methods):
+                        continue
+
+                    all_path_operations[path].operations.append(operation)
+                    all_path_operations[path].is_async = (
+                        all_path_operations[path].is_async or operation.is_async
+                    )
+
+        return all_path_operations
+
     def add_router(
         self,
         prefix: str,

tests/test_router_multiple_methods_same_path.py

@@ -0,0 +1,114 @@
+from ninja import NinjaAPI, Router
+from ninja.testing import TestClient
+
+
+def test_multiple_routers_same_path_different_methods():
+    api = NinjaAPI()
+
+    router1 = Router()
+
+    @router1.get("/items")
+    def get_items(request):
+        return {"method": "GET", "router": 1}
+
+    @router1.post("/items")
+    def create_item(request):
+        return {"method": "POST", "router": 1}
+
+    router2 = Router()
+
+    @router2.put("/items")
+    def update_item(request):
+        return {"method": "PUT", "router": 2}
+
+    @router2.delete("/items")
+    def delete_item(request):
+        return {"method": "DELETE", "router": 2}
+
+    api.add_router("", router1)
+    api.add_router("", router2)
+
+    client = TestClient(api)
+
+    response = client.get("/items")
+    assert response.status_code == 200
+    assert response.json() == {"method": "GET", "router": 1}
+
+    response = client.post("/items")
+    assert response.status_code == 200
+    assert response.json() == {"method": "POST", "router": 1}
+
+    response = client.put("/items")
+    assert response.status_code == 200
+    assert response.json() == {"method": "PUT", "router": 2}
+
+    response = client.delete("/items")
+    assert response.status_code == 200
+    assert response.json() == {"method": "DELETE", "router": 2}
+
+    # unsupported method returns 405
+    response = client.patch("/items")
+    assert response.status_code == 405
+
+
+def test_api_and_router_same_path_different_methods():
+    api = NinjaAPI()
+
+    @api.get("/users")
+    def get_users(request):
+        return {"method": "GET", "source": "api"}
+
+    router = Router()
+
+    @router.put("/users")
+    def update_user(request):
+        return {"method": "PUT", "source": "router"}
+
+    @router.delete("/users")
+    def delete_user(request):
+        return {"method": "DELETE", "source": "router"}
+
+    api.add_router("", router)
+
+    client = TestClient(api)
+
+    response = client.get("/users")
+    assert response.status_code == 200
+    assert response.json() == {"method": "GET", "source": "api"}
+
+    response = client.put("/users")
+    assert response.status_code == 200
+    assert response.json() == {"method": "PUT", "source": "router"}
+
+    response = client.delete("/users")
+    assert response.status_code == 200
+    assert response.json() == {"method": "DELETE", "source": "router"}
+
+    # unsupported method returns 405
+    response = client.post("/users")
+    assert response.status_code == 405
+
+
+def test_overlapping_methods_different_routers():
+    api = NinjaAPI()
+
+    router1 = Router()
+
+    @router1.get("/overlap")
+    def get_overlap_1(request):
+        return {"source": "router1"}
+
+    router2 = Router()
+
+    @router2.get("/overlap")
+    def get_overlap_2(request):
+        return {"source": "router2"}
+
+    api.add_router("", router1)
+    api.add_router("", router2)
+
+    client = TestClient(api)
+
+    # first router's handler should be used
+    response = client.get("/overlap")
+    assert response.status_code == 200