[next] Add enhanceApp / enhanceComponent

https://github.com/zeit/next.js/tree/cf31021e25f8d90f91ef3f7cb4f36a46d52fc56d#customizing-renderpage
https://github.com/zeit/next.js/blob/7e7be0e2e8419b28d9c562e04cba1fc52a39f086/packages/next-server/server/render.tsx#L13-L32

types/next/document.d.ts

@@ -27,8 +27,15 @@ export type Enhancer<E extends PageProps = AnyPageProps, P extends any = E> = (
  */
 export interface NextDocumentContext<Q extends DefaultQuery = DefaultQuery> extends NextContext<Q> {
     /** A callback that executes the actual React rendering logic (synchronously) */
-    renderPage<E extends PageProps = AnyPageProps, P extends any = E>(
-        enhancer?: Enhancer<E, P> // tslint:disable-line no-unnecessary-generics
+    renderPage<
+        E extends PageProps = AnyPageProps,
+        P = E,
+        EA extends PageProps = AnyPageProps,
+        PA = EA,
+    >(
+        enhancer?:
+            | Enhancer<E, P> // tslint:disable-line no-unnecessary-generics
+            | { enhanceApp?: Enhancer<EA, PA>; enhanceComponent?: Enhancer<E, P> } // tslint:disable-line no-unnecessary-generics
     ): RenderPageResponse;
 }
 

types/next/test/next-document-tests.tsx

@@ -38,12 +38,20 @@ class MyDoc extends Document<WithUrlProps> {
     static async getInitialProps(ctx: NextDocumentContext) {
         const { req, renderPage } = ctx;
 
-        // without callback
+        // without enhancer
         const _page = renderPage();
 
-        // with callback
-        const enhancer: Enhancer<PageProps, {}> = App => props => <App />;
-        const { html, head, buildManifest } = renderPage(enhancer);
+        // with component enhancer
+        const enhancer: Enhancer<PageProps, {}> = Component => props => <Component />;
+        const _enhancedPage = renderPage(enhancer);
+
+        // with app and component enhancers
+        const enhanceApp: Enhancer<PageProps, {}> = App => props => <App />;
+        const enhanceComponent: Enhancer<PageProps, {}> = Component => props => <Component />;
+        const { html, head, buildManifest } = renderPage({
+            enhanceApp,
+            enhanceComponent
+        });
 
         const initialProps = await Document.getInitialProps(ctx);