chore: move transport to object messages (#1567)

src/chromium/crBrowser.ts

@@ -243,7 +243,7 @@ export class CRBrowser extends platform.EventEmitter implements Browser {
     return this._clientRootSessionPromise;
   }
 
-  _setDebugFunction(debugFunction: (message: string) => void) {
+  _setDebugFunction(debugFunction: platform.DebuggerType) {
     this._connection._debugProtocol = debugFunction;
   }
 }

src/chromium/crConnection.ts

@@ -17,7 +17,7 @@
 
 import { assert } from '../helper';
 import * as platform from '../platform';
-import { ConnectionTransport } from '../transport';
+import { ConnectionTransport, ProtocolMessage } from '../transport';
 import { Protocol } from './protocol';
 
 export const ConnectionEvents = {
@@ -34,7 +34,7 @@ export class CRConnection extends platform.EventEmitter {
   private readonly _sessions = new Map<string, CRSession>();
   readonly rootSession: CRSession;
   _closed = false;
-  _debugProtocol: (message: string) => void;
+  _debugProtocol: platform.DebuggerType;
 
   constructor(transport: ConnectionTransport) {
     super();
@@ -55,37 +55,37 @@ export class CRConnection extends platform.EventEmitter {
     return this._sessions.get(sessionId) || null;
   }
 
-  _rawSend(sessionId: string, message: any): number {
+  _rawSend(sessionId: string, message: ProtocolMessage): number {
     const id = ++this._lastId;
     message.id = id;
     if (sessionId)
       message.sessionId = sessionId;
-    const data = JSON.stringify(message);
+    if (this._debugProtocol.enabled)
-    this._debugProtocol('SEND ► ' + (rewriteInjectedScriptEvaluationLog(message) || data));
+      this._debugProtocol('SEND ► ' + rewriteInjectedScriptEvaluationLog(message));
-    this._transport.send(data);
+    this._transport.send(message);
     return id;
   }
 
-  async _onMessage(message: string) {
+  async _onMessage(message: ProtocolMessage) {
-    this._debugProtocol('◀ RECV ' + message);
+    if (this._debugProtocol.enabled)
-    const object = JSON.parse(message);
+      this._debugProtocol('◀ RECV ' + rewriteInjectedScriptEvaluationLog(message));
-    if (object.id === kBrowserCloseMessageId)
+    if (message.id === kBrowserCloseMessageId)
       return;
-    if (object.method === 'Target.attachedToTarget') {
+    if (message.method === 'Target.attachedToTarget') {
-      const sessionId = object.params.sessionId;
+      const sessionId = message.params.sessionId;
-      const rootSessionId = object.sessionId || '';
+      const rootSessionId = message.sessionId || '';
-      const session = new CRSession(this, rootSessionId, object.params.targetInfo.type, sessionId);
+      const session = new CRSession(this, rootSessionId, message.params.targetInfo.type, sessionId);
       this._sessions.set(sessionId, session);
-    } else if (object.method === 'Target.detachedFromTarget') {
+    } else if (message.method === 'Target.detachedFromTarget') {
-      const session = this._sessions.get(object.params.sessionId);
+      const session = this._sessions.get(message.params.sessionId);
       if (session) {
         session._onClosed();
-        this._sessions.delete(object.params.sessionId);
+        this._sessions.delete(message.params.sessionId);
       }
     }
-    const session = this._sessions.get(object.sessionId || '');
+    const session = this._sessions.get(message.sessionId || '');
     if (session)
-      session._onMessage(object);
+      session._onMessage(message);
   }
 
   _onClose() {
@@ -156,12 +156,12 @@ export class CRSession extends platform.EventEmitter {
     });
   }
 
-  _onMessage(object: { id?: number; method: string; params: any; error: { message: string; data: any; }; result?: any; }) {
+  _onMessage(object: ProtocolMessage) {
     if (object.id && this._callbacks.has(object.id)) {
       const callback = this._callbacks.get(object.id)!;
       this._callbacks.delete(object.id);
       if (object.error)
-        callback.reject(createProtocolError(callback.error, callback.method, object));
+        callback.reject(createProtocolError(callback.error, callback.method, object.error));
       else
         callback.resolve(object.result);
     } else {
@@ -188,10 +188,10 @@ export class CRSession extends platform.EventEmitter {
   }
 }
 
-function createProtocolError(error: Error, method: string, object: { error: { message: string; data: any; }; }): Error {
+function createProtocolError(error: Error, method: string, protocolError: { message: string; data: any; }): Error {
-  let message = `Protocol error (${method}): ${object.error.message}`;
+  let message = `Protocol error (${method}): ${protocolError.message}`;
-  if ('data' in object.error)
+  if ('data' in protocolError)
-    message += ` ${object.error.data}`;
+    message += ` ${protocolError.data}`;
   return rewriteError(error, message);
 }
 
@@ -200,9 +200,10 @@ function rewriteError(error: Error, message: string): Error {
   return error;
 }
 
-function rewriteInjectedScriptEvaluationLog(message: any): string | undefined {
+function rewriteInjectedScriptEvaluationLog(message: ProtocolMessage): string {
   // Injected script is very long and clutters protocol logs.
   // To increase development velocity, we skip replace it with short description in the log.
   if (message.method === 'Runtime.evaluate' && message.params && message.params.expression && message.params.expression.includes('src/injected/injected.ts'))
     return `{"id":${message.id} [evaluate injected script]}`;
+  return JSON.stringify(message);
 }

src/firefox/ffBrowser.ts

@@ -149,7 +149,7 @@ export class FFBrowser extends platform.EventEmitter implements Browser {
     await disconnected;
   }
 
-  _setDebugFunction(debugFunction: (message: string) => void) {
+  _setDebugFunction(debugFunction: platform.DebuggerType) {
     this._connection._debugProtocol = debugFunction;
   }
 }

src/firefox/ffConnection.ts

@@ -17,7 +17,7 @@
 
 import {assert} from '../helper';
 import * as platform from '../platform';
-import { ConnectionTransport } from '../transport';
+import { ConnectionTransport, ProtocolMessage } from '../transport';
 import { Protocol } from './protocol';
 
 export const ConnectionEvents = {
@@ -33,7 +33,7 @@ export class FFConnection extends platform.EventEmitter {
   private _callbacks: Map<number, {resolve: Function, reject: Function, error: Error, method: string}>;
   private _transport: ConnectionTransport;
   readonly _sessions: Map<string, FFSession>;
-  _debugProtocol: (message: string) => void = platform.debug('pw:protocol');
+  _debugProtocol: platform.DebuggerType = platform.debug('pw:protocol');
   _closed: boolean;
 
   on: <T extends keyof Protocol.Events | symbol>(event: T, listener: (payload: T extends symbol ? any : Protocol.Events[T extends keyof Protocol.Events ? T : never]) => void) => this;
@@ -76,33 +76,33 @@ export class FFConnection extends platform.EventEmitter {
     return ++this._lastId;
   }
 
-  _rawSend(message: any) {
+  _rawSend(message: ProtocolMessage) {
-    const data = JSON.stringify(message);
+    if (this._debugProtocol.enabled)
-    this._debugProtocol('SEND ► ' + (rewriteInjectedScriptEvaluationLog(message) || data));
+      this._debugProtocol('SEND ► ' + rewriteInjectedScriptEvaluationLog(message));
-    this._transport.send(data);
+    this._transport.send(message);
   }
 
-  async _onMessage(message: string) {
+  async _onMessage(message: ProtocolMessage) {
-    this._debugProtocol('◀ RECV ' + message);
+    if (this._debugProtocol.enabled)
-    const object = JSON.parse(message);
+      this._debugProtocol('◀ RECV ' + message);
-    if (object.id === kBrowserCloseMessageId)
+    if (message.id === kBrowserCloseMessageId)
       return;
-    if (object.sessionId) {
+    if (message.sessionId) {
-      const session = this._sessions.get(object.sessionId);
+      const session = this._sessions.get(message.sessionId);
       if (session)
-        session.dispatchMessage(object);
+        session.dispatchMessage(message);
-    } else if (object.id) {
+    } else if (message.id) {
-      const callback = this._callbacks.get(object.id);
+      const callback = this._callbacks.get(message.id);
       // Callbacks could be all rejected if someone has called `.dispose()`.
       if (callback) {
-        this._callbacks.delete(object.id);
+        this._callbacks.delete(message.id);
-        if (object.error)
+        if (message.error)
-          callback.reject(createProtocolError(callback.error, callback.method, object));
+          callback.reject(createProtocolError(callback.error, callback.method, message.error));
         else
-          callback.resolve(object.result);
+          callback.resolve(message.result);
       }
     } else {
-      Promise.resolve().then(() => this.emit(object.method, object.params));
+      Promise.resolve().then(() => this.emit(message.method, message.params));
     }
   }
 
@@ -176,12 +176,12 @@ export class FFSession extends platform.EventEmitter {
     });
   }
 
-  dispatchMessage(object: { id?: number; method: string; params: object; error: { message: string; data: any; }; result?: any; }) {
+  dispatchMessage(object: ProtocolMessage) {
     if (object.id && this._callbacks.has(object.id)) {
       const callback = this._callbacks.get(object.id)!;
       this._callbacks.delete(object.id);
       if (object.error)
-        callback.reject(createProtocolError(callback.error, callback.method, object));
+        callback.reject(createProtocolError(callback.error, callback.method, object.error));
       else
         callback.resolve(object.result);
     } else {
@@ -200,10 +200,10 @@ export class FFSession extends platform.EventEmitter {
   }
 }
 
-function createProtocolError(error: Error, method: string, object: { error: { message: string; data: any; }; }): Error {
+function createProtocolError(error: Error, method: string, protocolError: { message: string; data: any; }): Error {
-  let message = `Protocol error (${method}): ${object.error.message}`;
+  let message = `Protocol error (${method}): ${protocolError.message}`;
-  if ('data' in object.error)
+  if ('data' in protocolError)
-    message += ` ${object.error.data}`;
+    message += ` ${protocolError.data}`;
   return rewriteError(error, message);
 }
 
@@ -212,9 +212,10 @@ function rewriteError(error: Error, message: string): Error {
   return error;
 }
 
-function rewriteInjectedScriptEvaluationLog(message: any): string | undefined {
+function rewriteInjectedScriptEvaluationLog(message: ProtocolMessage): string {
   // Injected script is very long and clutters protocol logs.
   // To increase development velocity, we skip replace it with short description in the log.
   if (message.method === 'Runtime.evaluate' && message.params && message.params.expression && message.params.expression.includes('src/injected/injected.ts'))
     return `{"id":${message.id} [evaluate injected script]}`;
+  return JSON.stringify(message);
 }

src/platform.ts

@@ -29,7 +29,7 @@ import * as NodeWebSocket from 'ws';
 import * as crypto from 'crypto';
 
 import { assert, helper } from './helper';
-import { ConnectionTransport } from './transport';
+import { ConnectionTransport, ProtocolMessage } from './transport';
 
 export const isNode = typeof process === 'object' && !!process && typeof process.versions === 'object' && !!process.versions && !!process.versions.node;
 
@@ -112,7 +112,8 @@ export const EventEmitter: typeof nodeEvents.EventEmitter = isNode ? nodeEvents.
 ) as any as typeof nodeEvents.EventEmitter;
 export type EventEmitterType = nodeEvents.EventEmitter;
 
-type DebugType = typeof nodeDebug;
+export type DebuggerType = nodeDebug.IDebugger;
+export type DebugType = nodeDebug.IDebug;
 export const debug: DebugType = isNode ? nodeDebug : (
   function debug(namespace: string) {
     return () => {};
@@ -322,7 +323,7 @@ export async function connectToWebsocket<T>(url: string, onopen: (transport: Con
 class WebSocketTransport implements ConnectionTransport {
   _ws: WebSocket;
 
-  onmessage?: (message: string) => void;
+  onmessage?: (message: ProtocolMessage) => void;
   onclose?: () => void;
 
   constructor(url: string) {
@@ -339,7 +340,7 @@ class WebSocketTransport implements ConnectionTransport {
     this._ws.addEventListener('message', event => {
       messageWrap(() => {
         if (this.onmessage)
-          this.onmessage.call(null, event.data);
+          this.onmessage.call(null, JSON.parse(event.data));
       });
     });
 
@@ -351,8 +352,8 @@ class WebSocketTransport implements ConnectionTransport {
     this._ws.addEventListener('error', () => {});
   }
 
-  send(message: string) {
+  send(message: ProtocolMessage) {
-    this._ws.send(message);
+    this._ws.send(JSON.stringify(message));
   }
 
   close() {

src/server/chromium.ts

@@ -115,7 +115,7 @@ export class Chromium implements BrowserType<CRBrowser> {
         // our connection ignores kBrowserCloseMessageId.
         const t = transport || await platform.connectToWebsocket(browserWSEndpoint!, async transport => transport);
         const message = { method: 'Browser.close', id: kBrowserCloseMessageId };
-        await t.send(JSON.stringify(message));
+        await t.send(message);
       },
       onkill: (exitCode, signal) => {
         if (browserServer)

src/server/firefox.ts

@@ -130,7 +130,7 @@ export class Firefox implements BrowserType<FFBrowser> {
         // our connection ignores kBrowserCloseMessageId.
         const transport = await platform.connectToWebsocket(browserWSEndpoint, async transport => transport);
         const message = { method: 'Browser.close', params: {}, id: kBrowserCloseMessageId };
-        await transport.send(JSON.stringify(message));
+        await transport.send(message);
       },
       onkill: (exitCode, signal) => {
         if (browserServer)

src/server/pipeTransport.ts

@@ -16,7 +16,7 @@
  */
 
 import { debugError, helper, RegisteredListener } from '../helper';
-import { ConnectionTransport } from '../transport';
+import { ConnectionTransport, ProtocolMessage } from '../transport';
 import { makeWaitForNextTask } from '../platform';
 
 export class PipeTransport implements ConnectionTransport {
@@ -26,7 +26,7 @@ export class PipeTransport implements ConnectionTransport {
   private _waitForNextTask = makeWaitForNextTask();
   private readonly _closeCallback: () => void;
 
-  onmessage?: (message: string) => void;
+  onmessage?: (message: ProtocolMessage) => void;
   onclose?: () => void;
 
   constructor(pipeWrite: NodeJS.WritableStream, pipeRead: NodeJS.ReadableStream, closeCallback: () => void) {
@@ -46,8 +46,8 @@ export class PipeTransport implements ConnectionTransport {
     this.onclose = undefined;
   }
 
-  send(message: string) {
+  send(message: ProtocolMessage) {
-    this._pipeWrite!.write(message);
+    this._pipeWrite!.write(JSON.stringify(message));
     this._pipeWrite!.write('\0');
   }
 
@@ -64,7 +64,7 @@ export class PipeTransport implements ConnectionTransport {
     const message = this._pendingMessage + buffer.toString(undefined, 0, end);
     this._waitForNextTask(() => {
       if (this.onmessage)
-        this.onmessage.call(null, message);
+        this.onmessage.call(null, JSON.parse(message));
     });
 
     let start = end + 1;
@@ -73,7 +73,7 @@ export class PipeTransport implements ConnectionTransport {
       const message = buffer.toString(undefined, start, end);
       this._waitForNextTask(() => {
         if (this.onmessage)
-          this.onmessage.call(null, message);
+          this.onmessage.call(null, JSON.parse(message));
       });
       start = end + 1;
       end = buffer.indexOf('\0', start);

src/server/webkit.ts

@@ -114,8 +114,7 @@ export class WebKit implements BrowserType<WKBrowser> {
         // We try to gracefully close to prevent crash reporting and core dumps.
         // Note that it's fine to reuse the pipe transport, since
         // our connection ignores kBrowserCloseMessageId.
-        const message = JSON.stringify({method: 'Playwright.close', params: {}, id: kBrowserCloseMessageId});
+        transport.send({method: 'Playwright.close', params: {}, id: kBrowserCloseMessageId});
-        transport.send(message);
       },
       onkill: (exitCode, signal) => {
         if (browserServer)
@@ -194,54 +193,53 @@ function wrapTransportWithWebSocket(transport: ConnectionTransport, port: number
   const sockets = new Set<ws>();
 
   transport.onmessage = message => {
-    const parsedMessage = JSON.parse(message);
+    if (typeof message.id === 'number') {
-    if ('id' in parsedMessage) {
+      if (message.id === -9999)
-      if (parsedMessage.id === -9999)
         return;
       // Process command response.
-      const value = idMixer.take(parsedMessage.id);
+      const value = idMixer.take(message.id);
       if (!value)
         return;
       const { id, socket } = value;
 
       if (!socket || socket.readyState === ws.CLOSING) {
         if (pendingBrowserContextCreations.has(id)) {
-          transport.send(JSON.stringify({
+          transport.send({
             id: ++SequenceNumberMixer._lastSequenceNumber,
             method: 'Playwright.deleteContext',
-            params: { browserContextId: parsedMessage.result.browserContextId }
+            params: { browserContextId: message.result.browserContextId }
-          }));
+          });
         }
         return;
       }
 
-      if (pendingBrowserContextCreations.has(parsedMessage.id)) {
+      if (pendingBrowserContextCreations.has(message.id)) {
         // Browser.createContext response -> establish context attribution.
-        browserContextIds.set(parsedMessage.result.browserContextId, socket);
+        browserContextIds.set(message.result.browserContextId, socket);
-        pendingBrowserContextCreations.delete(parsedMessage.id);
+        pendingBrowserContextCreations.delete(message.id);
       }
 
-      const deletedContextId = pendingBrowserContextDeletions.get(parsedMessage.id);
+      const deletedContextId = pendingBrowserContextDeletions.get(message.id);
       if (deletedContextId) {
         // Browser.deleteContext response -> remove context attribution.
         browserContextIds.delete(deletedContextId);
-        pendingBrowserContextDeletions.delete(parsedMessage.id);
+        pendingBrowserContextDeletions.delete(message.id);
       }
 
-      parsedMessage.id = id;
+      message.id = id;
-      socket.send(JSON.stringify(parsedMessage));
+      socket.send(JSON.stringify(message));
       return;
     }
 
     // Process notification response.
-    const { method, params, pageProxyId } = parsedMessage;
+    const { method, params, pageProxyId } = message;
     if (pageProxyId) {
       const socket = pageProxyIds.get(pageProxyId);
       if (!socket || socket.readyState === ws.CLOSING) {
         // Drop unattributed messages on the floor.
         return;
       }
-      socket.send(message);
+      socket.send(JSON.stringify(message));
       return;
     }
     if (method === 'Playwright.pageProxyCreated') {
@@ -251,20 +249,20 @@ function wrapTransportWithWebSocket(transport: ConnectionTransport, port: number
         return;
       }
       pageProxyIds.set(params.pageProxyInfo.pageProxyId, socket);
-      socket.send(message);
+      socket.send(JSON.stringify(message));
       return;
     }
     if (method === 'Playwright.pageProxyDestroyed') {
       const socket = pageProxyIds.get(params.pageProxyId);
       pageProxyIds.delete(params.pageProxyId);
       if (socket && socket.readyState !== ws.CLOSING)
-        socket.send(message);
+        socket.send(JSON.stringify(message));
       return;
     }
     if (method === 'Playwright.provisionalLoadFailed') {
       const socket = pageProxyIds.get(params.pageProxyId);
       if (socket && socket.readyState !== ws.CLOSING)
-        socket.send(message);
+        socket.send(JSON.stringify(message));
       return;
     }
   };
@@ -280,7 +278,7 @@ function wrapTransportWithWebSocket(transport: ConnectionTransport, port: number
       const parsedMessage = JSON.parse(Buffer.from(message).toString());
       const { id, method, params } = parsedMessage;
       const seqNum = idMixer.generate({ id, socket });
-      transport.send(JSON.stringify({ ...parsedMessage, id: seqNum }));
+      transport.send({ ...parsedMessage, id: seqNum });
       if (method === 'Playwright.createContext')
         pendingBrowserContextCreations.add(seqNum);
       if (method === 'Playwright.deleteContext')
@@ -294,11 +292,11 @@ function wrapTransportWithWebSocket(transport: ConnectionTransport, port: number
       }
       for (const [browserContextId, s] of browserContextIds) {
         if (s === socket) {
-          transport.send(JSON.stringify({
+          transport.send({
             id: ++SequenceNumberMixer._lastSequenceNumber,
             method: 'Playwright.deleteContext',
             params: { browserContextId }
-          }));
+          });
           browserContextIds.delete(browserContextId);
         }
       }

src/transport.ts

@@ -15,10 +15,20 @@
  * limitations under the License.
  */
 
+export type ProtocolMessage = {
+  id?: number;
+  method: string;
+  params?: any;
+  sessionId?: string;
+  error?: { message: string; data: any; };
+  result?: any;
+  pageProxyId?: string;
+};
+
 export interface ConnectionTransport {
-  send(s: string): void;
+  send(s: ProtocolMessage): void;
   close(): void;  // Note: calling close is expected to issue onclose at some point.
-  onmessage?: (message: string) => void,
+  onmessage?: (message: ProtocolMessage) => void,
   onclose?: () => void,
 }
 
@@ -26,7 +36,7 @@ export class SlowMoTransport {
   private readonly _delay: number;
   private readonly _delegate: ConnectionTransport;
 
-  onmessage?: (message: string) => void;
+  onmessage?: (message: ProtocolMessage) => void;
   onclose?: () => void;
 
   static wrap(transport: ConnectionTransport, delay?: number): ConnectionTransport {
@@ -40,7 +50,7 @@ export class SlowMoTransport {
     this._delegate.onclose = this._onClose.bind(this);
   }
 
-  private _onmessage(message: string) {
+  private _onmessage(message: ProtocolMessage) {
     if (this.onmessage)
       this.onmessage(message);
   }
@@ -52,7 +62,7 @@ export class SlowMoTransport {
     this._delegate.onclose = undefined;
   }
 
-  send(s: string) {
+  send(s: ProtocolMessage) {
     setTimeout(() => {
       if (this._delegate.onmessage)
         this._delegate.send(s);
@@ -68,14 +78,14 @@ export class DeferWriteTransport implements ConnectionTransport {
   private _delegate: ConnectionTransport;
   private _readPromise: Promise<void>;
 
-  onmessage?: (message: string) => void;
+  onmessage?: (message: ProtocolMessage) => void;
   onclose?: () => void;
 
   constructor(transport: ConnectionTransport) {
     this._delegate = transport;
     let callback: () => void;
     this._readPromise = new Promise(f => callback = f);
-    this._delegate.onmessage = s => {
+    this._delegate.onmessage = (s: ProtocolMessage) => {
       callback();
       if (this.onmessage)
         this.onmessage(s);
@@ -86,7 +96,7 @@ export class DeferWriteTransport implements ConnectionTransport {
     };
   }
 
-  async send(s: string) {
+  async send(s: ProtocolMessage) {
     await this._readPromise;
     this._delegate.send(s);
   }

src/webkit/wkBrowser.ts

@@ -186,7 +186,7 @@ export class WKBrowser extends platform.EventEmitter implements Browser {
     await disconnected;
   }
 
-  _setDebugFunction(debugFunction: (message: string) => void) {
+  _setDebugFunction(debugFunction: platform.DebuggerType) {
     this._connection._debugProtocol = debugFunction;
   }
 }

src/webkit/wkConnection.ts

@@ -17,7 +17,7 @@
 
 import { assert } from '../helper';
 import * as platform from '../platform';
-import { ConnectionTransport } from '../transport';
+import { ConnectionTransport, ProtocolMessage } from '../transport';
 import { Protocol } from './protocol';
 
 // WKPlaywright uses this special id to issue Browser.close command which we
@@ -34,7 +34,7 @@ export class WKConnection {
   private readonly _onDisconnect: () => void;
   private _lastId = 0;
   private _closed = false;
-  _debugProtocol: (message: string) => void = platform.debug('pw:protocol');
+  _debugProtocol: platform.DebuggerType = platform.debug('pw:protocol');
 
   readonly browserSession: WKSession;
 
@@ -53,23 +53,23 @@ export class WKConnection {
     return ++this._lastId;
   }
 
-  rawSend(message: any) {
+  rawSend(message: ProtocolMessage) {
-    const data = JSON.stringify(message);
+    if (this._debugProtocol.enabled)
-    this._debugProtocol('SEND ► ' + (rewriteInjectedScriptEvaluationLog(message) || data));
+      this._debugProtocol('SEND ► ' + rewriteInjectedScriptEvaluationLog(message));
-    this._transport.send(data);
+    this._transport.send(message);
   }
 
-  private _dispatchMessage(message: string) {
+  private _dispatchMessage(message: ProtocolMessage) {
-    this._debugProtocol('◀ RECV ' + message);
+    if (this._debugProtocol.enabled)
-    const object = JSON.parse(message);
+      this._debugProtocol('◀ RECV ' + message);
-    if (object.id === kBrowserCloseMessageId)
+    if (message.id === kBrowserCloseMessageId)
       return;
-    if (object.pageProxyId) {
+    if (message.pageProxyId) {
-      const payload: PageProxyMessageReceivedPayload = { message: object, pageProxyId: object.pageProxyId };
+      const payload: PageProxyMessageReceivedPayload = { message: message, pageProxyId: message.pageProxyId };
       this.browserSession.dispatchMessage({ method: kPageProxyMessageReceived, params: payload });
       return;
     }
-    this.browserSession.dispatchMessage(object);
+    this.browserSession.dispatchMessage(message);
   }
 
   _onClose() {
@@ -151,7 +151,7 @@ export class WKSession extends platform.EventEmitter {
       const callback = this._callbacks.get(object.id)!;
       this._callbacks.delete(object.id);
       if (object.error)
-        callback.reject(createProtocolError(callback.error, callback.method, object));
+        callback.reject(createProtocolError(callback.error, callback.method, object.error));
       else
         callback.resolve(object.result);
     } else if (object.id) {
@@ -163,10 +163,10 @@ export class WKSession extends platform.EventEmitter {
   }
 }
 
-export function createProtocolError(error: Error, method: string, object: { error: { message: string; data: any; }; }): Error {
+export function createProtocolError(error: Error, method: string, protocolError: { message: string; data: any; }): Error {
-  let message = `Protocol error (${method}): ${object.error.message}`;
+  let message = `Protocol error (${method}): ${protocolError.message}`;
-  if ('data' in object.error)
+  if ('data' in protocolError)
-    message += ` ${JSON.stringify(object.error.data)}`;
+    message += ` ${JSON.stringify(protocolError.data)}`;
   return rewriteError(error, message);
 }
 
@@ -179,9 +179,10 @@ export function isSwappedOutError(e: Error) {
   return e.message.includes('Target was swapped out.');
 }
 
-function rewriteInjectedScriptEvaluationLog(message: any): string | undefined {
+function rewriteInjectedScriptEvaluationLog(message: any): string {
   // Injected script is very long and clutters protocol logs.
   // To increase development velocity, we skip replace it with short description in the log.
   if (message.params && message.params.message && message.params.message.includes('Runtime.evaluate') && message.params.message.includes('src/injected/injected.ts'))
     return `{"id":${message.id},"method":"${message.method}","params":{"message":[evaluate injected script],"targetId":"${message.params.targetId}"},"pageProxyId":${message.pageProxyId}}`;
+  return JSON.stringify(message);
 }