Enhance route.lazy return type (#10634)

* Enahnce route.lazy return type

* Fix upstream type in RR

.changeset/route-lazy-type.md

@@ -0,0 +1,5 @@
+---
+"@remix-run/router": patch
+---
+
+Enhance the return type of `Route.lazy` to prohibit returning an empty object

packages/react-router/lib/context.ts

@@ -10,7 +10,6 @@ import type {
   StaticHandlerContext,
   To,
   TrackedPromise,
-  LazyRouteFunction,
 } from "@remix-run/router";
 import type { Action as NavigationType } from "@remix-run/router";
 
@@ -31,7 +30,7 @@ export interface IndexRouteObject {
   errorElement?: React.ReactNode | null;
   Component?: React.ComponentType | null;
   ErrorBoundary?: React.ComponentType | null;
-  lazy?: LazyRouteFunction<IndexRouteObject>;
+  lazy?: AgnosticIndexRouteObject["lazy"];
 }
 
 export interface NonIndexRouteObject {
@@ -49,7 +48,7 @@ export interface NonIndexRouteObject {
   errorElement?: React.ReactNode | null;
   Component?: React.ComponentType | null;
   ErrorBoundary?: React.ComponentType | null;
-  lazy?: LazyRouteFunction<NonIndexRouteObject>;
+  lazy?: AgnosticNonIndexRouteObject["lazy"];
 }
 
 export type RouteObject = IndexRouteObject | NonIndexRouteObject;

packages/router/utils.ts

@@ -239,12 +239,19 @@ export const immutableRouteKeys = new Set<ImmutableRouteKey>([
   "children",
 ]);
 
+type RequireOne<T, Key = keyof T> = Exclude<
+  {
+    [K in keyof T]: K extends Key ? Omit<T, K> & Required<Pick<T, K>> : never;
+  }[keyof T],
+  undefined
+>;
+
 /**
  * lazy() function to load a route definition, which can add non-matching
  * related properties to a route
  */
 export interface LazyRouteFunction<R extends AgnosticRouteObject> {
-  (): Promise<Omit<R, ImmutableRouteKey>>;
+  (): Promise<RequireOne<Omit<R, ImmutableRouteKey>>>;
 }
 
 /**