feat(nextjs): Introduce auth().protect() for App Router

Allow per page protection in app router. This utility will automatically throw a 404 error if user is not authorized or authenticated.
When `auth().protect()` is called
- inside a page or layout file it will render the nearest `not-found` component set by the developer
- inside a route handler it will return empty response body with a 404 status code

packages/nextjs/src/app-router/server/auth.ts

@@ -1,12 +1,82 @@
+import type { SignedInAuthObject, SignedOutAuthObject } from '@clerk/backend';
+import type {
+  CheckAuthorizationWithCustomPermissions,
+  OrganizationCustomPermission,
+  OrganizationCustomRole,
+} from '@clerk/types';
+import { notFound } from 'next/navigation';
+
 import { authAuthHeaderMissing } from '../../server/errors';
 import { buildClerkProps, createGetAuth } from '../../server/getAuth';
+import type { AuthObjectWithoutResources } from '../../server/types';
 import { buildRequestLike } from './utils';
 
 export const auth = () => {
-  return createGetAuth({
+  const authObject = createGetAuth({
     debugLoggerName: 'auth()',
     noAuthStatusMessage: authAuthHeaderMissing(),
-  })(buildRequestLike());
+  })(buildRequestLike()) as
+    | AuthObjectWithoutResources<
+        SignedInAuthObject & {
+          protect: (
+            params?:
+              | {
+                  role: OrganizationCustomRole;
+                  permission?: never;
+                }
+              | {
+                  role?: never;
+                  permission: OrganizationCustomPermission;
+                }
+              | ((has: CheckAuthorizationWithCustomPermissions) => boolean),
+          ) => AuthObjectWithoutResources<SignedInAuthObject>;
+        }
+      >
+    /**
+     * Add a comment
+     */
+    | AuthObjectWithoutResources<
+        SignedOutAuthObject & {
+          protect: never;
+        }
+      >;
+
+  authObject.protect = params => {
+    /**
+     * User is not authenticated
+     */
+    if (!authObject.userId) {
+      notFound();
+    }
+
+    /**
+     * User is authenticated
+     */
+    if (!params) {
+      return { ...authObject };
+    }
+
+    /**
+     * if a function is passed and returns false then throw not found
+     */
+    if (typeof params === 'function') {
+      if (params(authObject.has)) {
+        return { ...authObject };
+      }
+      return notFound();
+    }
+
+    /**
+     * Checking if user is authorized when permission or role is passed
+     */
+    if (authObject.has(params)) {
+      return { ...authObject };
+    }
+
+    notFound();
+  };
+
+  return authObject;
 };
 
 export const initialState = () => {

packages/nextjs/src/server/getAuth.ts

@@ -1,4 +1,4 @@
-import type { AuthObject, Organization, Session, SignedInAuthObject, SignedOutAuthObject, User } from '@clerk/backend';
+import type { Organization, Session, SignedInAuthObject, SignedOutAuthObject, User } from '@clerk/backend';
 import {
   AuthStatus,
   constants,
@@ -12,11 +12,9 @@ import {
 import { withLogger } from '../utils/debugLogger';
 import { API_URL, API_VERSION, SECRET_KEY } from './constants';
 import { getAuthAuthHeaderMissing } from './errors';
-import type { RequestLike } from './types';
+import type { AuthObjectWithoutResources, RequestLike } from './types';
 import { getAuthKeyFromRequest, getCookie, getHeader, injectSSRStateIntoObject } from './utils';
 
-type AuthObjectWithoutResources<T extends AuthObject> = Omit<T, 'user' | 'organization' | 'session'>;
-
 export const createGetAuth = ({
   debugLoggerName,
   noAuthStatusMessage,

packages/nextjs/src/server/types.ts

@@ -1,4 +1,4 @@
-import type { OptionalVerifyTokenOptions } from '@clerk/backend';
+import type { AuthObject, OptionalVerifyTokenOptions } from '@clerk/backend';
 import type { MultiDomainAndOrProxy } from '@clerk/types';
 import type { IncomingMessage } from 'http';
 import type { NextApiRequest } from 'next';
@@ -20,3 +20,5 @@ export type WithAuthOptions = OptionalVerifyTokenOptions &
   };
 
 export type NextMiddlewareResult = Awaited<ReturnType<NextMiddleware>>;
+
+export type AuthObjectWithoutResources<T extends AuthObject> = Omit<T, 'user' | 'organization' | 'session'>;