Provide url rewritten in onPreRouting interceptor (elastic#80810)

* keep url rewritten in onPreRouting interceptor

* update docs

* add test on undefined

docs/development/core/server/kibana-plugin-core-server.kibanarequest.md

@@ -30,6 +30,7 @@ export declare class KibanaRequest<Params = unknown, Query = unknown, Body = unk
 |  [isSystemRequest](./kibana-plugin-core-server.kibanarequest.issystemrequest.md) |  | <code>boolean</code> | Whether or not the request is a "system request" rather than an application-level request. Can be set on the client using the <code>HttpFetchOptions#asSystemRequest</code> option. |
 |  [params](./kibana-plugin-core-server.kibanarequest.params.md) |  | <code>Params</code> |  |
 |  [query](./kibana-plugin-core-server.kibanarequest.query.md) |  | <code>Query</code> |  |
+|  [rewrittenUrl](./kibana-plugin-core-server.kibanarequest.rewrittenurl.md) |  | <code>Url</code> | URL rewritten in onPreRouting request interceptor. |
 |  [route](./kibana-plugin-core-server.kibanarequest.route.md) |  | <code>RecursiveReadonly&lt;KibanaRequestRoute&lt;Method&gt;&gt;</code> | matched route details |
 |  [socket](./kibana-plugin-core-server.kibanarequest.socket.md) |  | <code>IKibanaSocket</code> | [IKibanaSocket](./kibana-plugin-core-server.ikibanasocket.md) |
 |  [url](./kibana-plugin-core-server.kibanarequest.url.md) |  | <code>Url</code> | a WHATWG URL standard object. |

docs/development/core/server/kibana-plugin-core-server.kibanarequest.rewrittenurl.md

@@ -0,0 +1,13 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [kibana-plugin-core-server](./kibana-plugin-core-server.md) &gt; [KibanaRequest](./kibana-plugin-core-server.kibanarequest.md) &gt; [rewrittenUrl](./kibana-plugin-core-server.kibanarequest.rewrittenurl.md)
+
+## KibanaRequest.rewrittenUrl property
+
+URL rewritten in onPreRouting request interceptor.
+
+<b>Signature:</b>
+
+```typescript
+readonly rewrittenUrl?: Url;
+```

src/core/server/http/integration_tests/lifecycle.test.ts

@@ -117,6 +117,62 @@ describe('OnPreRouting', () => {
     expect(urlAfterForwarding).toBe('/redirectUrl');
   });
 
+  it('provides original request url', async () => {
+    const { registerOnPreRouting, server: innerServer, createRouter } = await server.setup(
+      setupDeps
+    );
+    const router = createRouter('/');
+
+    router.get({ path: '/login', validate: false }, (context, req, res) => {
+      return res.ok({ body: { rewrittenUrl: req.rewrittenUrl?.path } });
+    });
+
+    registerOnPreRouting((req, res, t) => t.rewriteUrl('/login'));
+
+    await server.start();
+
+    await supertest(innerServer.listener)
+      .get('/initial?name=foo')
+      .expect(200, { rewrittenUrl: '/initial?name=foo' });
+  });
+
+  it('provides original request url if rewritten several times', async () => {
+    const { registerOnPreRouting, server: innerServer, createRouter } = await server.setup(
+      setupDeps
+    );
+    const router = createRouter('/');
+
+    router.get({ path: '/reroute-2', validate: false }, (context, req, res) => {
+      return res.ok({ body: { rewrittenUrl: req.rewrittenUrl?.path } });
+    });
+
+    registerOnPreRouting((req, res, t) => t.rewriteUrl('/reroute-1'));
+    registerOnPreRouting((req, res, t) => t.rewriteUrl('/reroute-2'));
+
+    await server.start();
+
+    await supertest(innerServer.listener)
+      .get('/initial?name=foo')
+      .expect(200, { rewrittenUrl: '/initial?name=foo' });
+  });
+
+  it('does not provide request url if interceptor does not rewrite url', async () => {
+    const { registerOnPreRouting, server: innerServer, createRouter } = await server.setup(
+      setupDeps
+    );
+    const router = createRouter('/');
+
+    router.get({ path: '/login', validate: false }, (context, req, res) => {
+      return res.ok({ body: { rewrittenUrl: req.rewrittenUrl?.path } });
+    });
+
+    registerOnPreRouting((req, res, t) => t.next());
+
+    await server.start();
+
+    await supertest(innerServer.listener).get('/login').expect(200, {});
+  });
+
   it('supports redirection from the interceptor', async () => {
     const { registerOnPreRouting, server: innerServer, createRouter } = await server.setup(
       setupDeps

src/core/server/http/lifecycle/on_pre_routing.ts

@@ -25,6 +25,7 @@ import {
   KibanaResponse,
   lifecycleResponseFactory,
   LifecycleResponseFactory,
+  KibanaRequestState,
 } from '../router';
 
 enum ResultType {
@@ -108,6 +109,9 @@ export function adoptToHapiOnRequest(fn: OnPreRoutingHandler, log: Logger) {
       }
 
       if (preRoutingResult.isRewriteUrl(result)) {
+        const appState = request.app as KibanaRequestState;
+        appState.rewrittenUrl = appState.rewrittenUrl ?? request.url;
+
         const { url } = result;
         request.setUrl(url);
         // We should update raw request as well since it can be proxied to the old platform

src/core/server/http/router/request.ts

@@ -45,6 +45,7 @@ export interface KibanaRouteOptions extends RouteOptionsApp {
 export interface KibanaRequestState extends ApplicationState {
   requestId: string;
   requestUuid: string;
+  rewrittenUrl?: Url;
 }
 
 /**
@@ -186,6 +187,11 @@ export class KibanaRequest<
     isAuthenticated: boolean;
   };
 
+  /**
+   * URL rewritten in onPreRouting request interceptor.
+   */
+  public readonly rewrittenUrl?: Url;
+
   /** @internal */
   protected readonly [requestSymbol]: Request;
 
@@ -199,10 +205,12 @@ export class KibanaRequest<
     private readonly withoutSecretHeaders: boolean
   ) {
     // The `requestId` and `requestUuid` properties will not be populated for requests that are 'faked' by internal systems that leverage
-    // KibanaRequest in conjunction with scoped Elaticcsearch and SavedObjectsClient in order to pass credentials.
+    // KibanaRequest in conjunction with scoped Elasticsearch and SavedObjectsClient in order to pass credentials.
     // In these cases, the ids default to a newly generated UUID.
-    this.id = (request.app as KibanaRequestState | undefined)?.requestId ?? uuid.v4();
-    this.uuid = (request.app as KibanaRequestState | undefined)?.requestUuid ?? uuid.v4();
+    const appState = request.app as KibanaRequestState | undefined;
+    this.id = appState?.requestId ?? uuid.v4();
+    this.uuid = appState?.requestUuid ?? uuid.v4();
+    this.rewrittenUrl = appState?.rewrittenUrl;
 
     this.url = request.url;
     this.headers = deepFreeze({ ...request.headers });

src/core/server/server.api.md

@@ -1043,6 +1043,7 @@ export class KibanaRequest<Params = unknown, Query = unknown, Body = unknown, Me
     readonly params: Params;
     // (undocumented)
     readonly query: Query;
+    readonly rewrittenUrl?: Url;
     readonly route: RecursiveReadonly<KibanaRequestRoute<Method>>;
     // (undocumented)
     readonly socket: IKibanaSocket;