[next-server v8.1] Add useRouter() hook (#35058)

* [next-server] Add useRouter() hook

* Add a test for useRouter

* Add missing semicolon

* Bump version to 8.1

* RouterProps → SingletonRouter

* SingletonRouter → RouterProps 😅

* Update types/next-server/router.d.ts

As suggested by @resir014

Co-Authored-By: kachkaev <alexander@kachkaev.ru>

* Fix linting

types/next-server/index.d.ts

@@ -1,4 +1,4 @@
-// Type definitions for next-server 8.0
+// Type definitions for next-server 8.1
 // Project: https://github.com/zeit/next.js/packages/next-server
 // Definitions by: Drew Hays <https://github.com/dru89>
 //                 Brice BERNARD <https://github.com/brikou>

types/next-server/router.d.ts

@@ -96,5 +96,8 @@ export function withRouter<T extends {}, Q = DefaultQuery>(
   Component: React.ComponentType<T & WithRouterProps<Q>>
 ): React.ComponentType<Omit<T, keyof WithRouterProps<Q>>>;
 
+// tslint:disable-next-line no-unnecessary-generics
+export function useRouter<Q = DefaultQuery>(): RouterProps<Q>;
+
 declare const Router: SingletonRouter;
 export default Router;

types/next-server/test/next-server-router-tests.tsx

@@ -1,4 +1,4 @@
-import Router, { withRouter, WithRouterProps } from "next-server/router";
+import Router, { useRouter, withRouter, WithRouterProps } from "next-server/router";
 import * as React from "react";
 import * as qs from "querystring";
 
@@ -154,4 +154,9 @@ const TestSFC3 = withRouter(({ router }) => {
     return <div>{router && router.query && router.query.test}</div>;
 });
 
+const TestHook = (() => {
+    const router = useRouter();
+    return <div>{router && router.query && router.query.test}</div>;
+});
+
 const res4 = <TestSFC3 />;