fix: fulfill intercepted response with empty body (#8151)

src/client/network.ts

@@ -265,7 +265,7 @@ export class Route extends ChannelOwner<channels.RouteChannel, channels.RouteIni
 
   async fulfill(options: { status?: number, headers?: Headers, contentType?: string, body?: string | Buffer, path?: string } = {}) {
     return this._wrapApiCall(async (channel: channels.RouteChannel) => {
-      let body = '';
+      let body = undefined;
       let isBase64 = false;
       let length = 0;
       if (options.path) {

src/server/firefox/ffNetworkManager.ts

@@ -179,15 +179,25 @@ const internalCauseToResourceType: {[key: string]: string} = {
 class InterceptableRequest {
   readonly request: network.Request;
   readonly _id: string;
+  private _redirectedTo: InterceptableRequest | undefined;
 
   constructor(frame: frames.Frame, redirectedFrom: InterceptableRequest | null, payload: Protocol.Network.requestWillBeSentPayload) {
     this._id = payload.requestId;
+    if (redirectedFrom)
+      redirectedFrom._redirectedTo = this;
     let postDataBuffer = null;
     if (payload.postData)
       postDataBuffer = Buffer.from(payload.postData, 'base64');
     this.request = new network.Request(frame, redirectedFrom ? redirectedFrom.request : null, payload.navigationId,
         payload.url, internalCauseToResourceType[payload.internalCause] || causeToResourceType[payload.cause] || 'other', payload.method, postDataBuffer, payload.headers);
   }
+
+  _finalRequest(): InterceptableRequest {
+    let request: InterceptableRequest = this;
+    while (request._redirectedTo)
+      request = request._redirectedTo;
+    return request;
+  }
 }
 
 class FFRouteImpl implements network.RouteDelegate {
@@ -199,12 +209,9 @@ class FFRouteImpl implements network.RouteDelegate {
     this._request = request;
   }
 
-  async responseBody(forFulfill: boolean): Promise<Buffer> {
-    // Empty buffer will result in the response being used.
-    if (forFulfill)
-      return Buffer.from('');
+  async responseBody(): Promise<Buffer> {
     const response = await this._session.send('Network.getResponseBody', {
-      requestId: this._request._id
+      requestId: this._request._finalRequest()._id
     });
     return Buffer.from(response.base64body, 'base64');
   }

src/server/network.ts

@@ -222,9 +222,9 @@ export class Route extends SdkObject {
     this._handled = true;
     let body = overrides.body;
     let isBase64 = overrides.isBase64 || false;
-    if (!body) {
+    if (body === undefined) {
       if (this._response) {
-        body = (await this._delegate.responseBody(true)).toString('utf8');
+        body = (await this._delegate.responseBody()).toString('utf8');
         isBase64 = false;
       } else {
         body = '';
@@ -254,7 +254,7 @@ export class Route extends SdkObject {
 
   async responseBody(): Promise<Buffer> {
     assert(!this._handled, 'Route is already handled!');
-    return this._delegate.responseBody(false);
+    return this._delegate.responseBody();
   }
 }
 
@@ -474,7 +474,7 @@ export interface RouteDelegate {
   abort(errorCode: string): Promise<void>;
   fulfill(response: types.NormalizedFulfillResponse): Promise<void>;
   continue(request: Request, overrides: types.NormalizedContinueOverrides): Promise<InterceptedResponse|null>;
-  responseBody(forFulfill: boolean): Promise<Buffer>;
+  responseBody(): Promise<Buffer>;
 }
 
 // List taken from https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml with extra 306 and 418 codes.

tests/page/page-request-intercept.spec.ts

@@ -40,6 +40,21 @@ it('should fulfill intercepted response', async ({page, server, browserName}) =>
   expect(await page.evaluate(() => document.body.textContent)).toBe('Yo, page!');
 });
 
+it('should fulfill response with empty body', async ({page, server, browserName}) => {
+  it.fail(browserName === 'firefox');
+  await page.route('**/*', async route => {
+    // @ts-expect-error
+    await route._intercept({});
+    await route.fulfill({
+      status: 201,
+      body: ''
+    });
+  });
+  const response = await page.goto(server.PREFIX + '/title.html');
+  expect(response.status()).toBe(201);
+  expect(await response.text()).toBe('');
+});
+
 it('should throw on continue after intercept', async ({page, server, browserName}) => {
   let routeCallback;
   const routePromise = new Promise<Route>(f => routeCallback = f);