fix: avoid unhandled promise rejection in WKSession.send (#770)

src/webkit/wkConnection.ts

@@ -119,20 +119,19 @@ export class WKSession extends platform.EventEmitter {
     this.once = super.once;
   }
 
-  send<T extends keyof Protocol.CommandParameters>(
+  async send<T extends keyof Protocol.CommandParameters>(
     method: T,
     params?: Protocol.CommandParameters[T]
   ): Promise<Protocol.CommandReturnValues[T]> {
     if (this._disposed)
-      return Promise.reject(new Error(`Protocol error (${method}): ${this.errorText}`));
+      throw new Error(`Protocol error (${method}): ${this.errorText}`);
     const id = this.connection.nextMessageId();
     const messageObj = { id, method, params };
     platform.debug('pw:wrapped:' + this.sessionId)('SEND ► ' + JSON.stringify(messageObj, null, 2));
-    const result = new Promise<Protocol.CommandReturnValues[T]>((resolve, reject) => {
+    this._rawSend(messageObj);
+    return new Promise<Protocol.CommandReturnValues[T]>((resolve, reject) => {
       this._callbacks.set(id, {resolve, reject, error: new Error(), method});
     });
-    this._rawSend(messageObj);
-    return result;
   }
 
   isDisposed(): boolean {

src/webkit/wkExecutionContext.ts

@@ -120,21 +120,17 @@ export class WKExecutionContext implements js.ExecutionContextDelegate {
       throw error;
     }
 
-    let callFunctionOnPromise;
-    try {
-      callFunctionOnPromise = this._session.send('Runtime.callFunctionOn', {
-        functionDeclaration: functionText + '\n' + suffix + '\n',
-        objectId: thisObjectId,
-        arguments: serializableArgs.map((arg: any) => this._convertArgument(arg)),
-        returnByValue: false,
-        emulateUserGesture: true
-      });
-    } catch (err) {
+    return this._session.send('Runtime.callFunctionOn', {
+      functionDeclaration: functionText + '\n' + suffix + '\n',
+      objectId: thisObjectId,
+      arguments: serializableArgs.map((arg: any) => this._convertArgument(arg)),
+      returnByValue: false,
+      emulateUserGesture: true
+    }).catch(err => {
       if (err instanceof TypeError && err.message.startsWith('Converting circular structure to JSON'))
         err.message += ' Are you passing a nested JSHandle?';
       throw err;
-    }
-    return callFunctionOnPromise.then(response => {
+    }).then(response => {
       if (response.result.type === 'object' && response.result.className === 'Promise') {
         return Promise.race([
           this._executionContextDestroyedPromise.then(() => contextDestroyedResult),

src/webkit/wkPage.ts

@@ -95,10 +95,24 @@ export class WKPage implements PageDelegate {
   // This method is called for provisional targets as well. The session passed as the parameter
   // may be different from the current session and may be destroyed without becoming current.
   async _initializeSession(session: WKSession, resourceTreeHandler: (r: Protocol.Page.getResourceTreeReturnValue) => void) {
-    const promises : Promise<any>[] = [
+    await this._initializeSessionMayThrow(session, resourceTreeHandler).catch(e => {
+      if (session.isDisposed())
+        return;
+      // Swallow initialization errors due to newer target swap in,
+      // since we will reinitialize again.
+      if (this._session === session)
+        throw e;
+    });
+  }
+
+  private async _initializeSessionMayThrow(session: WKSession, resourceTreeHandler: (r: Protocol.Page.getResourceTreeReturnValue) => void) {
+    const [, frameTree] = await Promise.all([
       // Page agent must be enabled before Runtime.
       session.send('Page.enable'),
-      session.send('Page.getResourceTree').then(resourceTreeHandler),
+      session.send('Page.getResourceTree'),
+    ]);
+    resourceTreeHandler(frameTree);
+    const promises : Promise<any>[] = [
       // Resource tree should be received before first execution context.
       session.send('Runtime.enable'),
       session.send('Page.createUserWorld', { name: UTILITY_WORLD_NAME }).catch(_ => {}),  // Worlds are per-process
@@ -129,19 +143,13 @@ export class WKPage implements PageDelegate {
       promises.push(session.send('Network.setExtraHTTPHeaders', { headers: this._page._state.extraHTTPHeaders }));
     if (this._page._state.hasTouch)
       promises.push(session.send('Page.setTouchEmulationEnabled', { enabled: true }));
-    await Promise.all(promises).catch(e => {
-      if (session.isDisposed())
-        return;
-      // Swallow initialization errors due to newer target swap in,
-      // since we will reinitialize again.
-      if (this._session === session)
-        throw e;
-    });
+    await Promise.all(promises);
   }
 
-  onProvisionalLoadStarted(provisionalSession: WKSession) {
+  initializeProvisionalPage(provisionalSession: WKSession) : Promise<void> {
     assert(!this._provisionalPage);
     this._provisionalPage = new WKProvisionalPage(provisionalSession, this);
+    return this._provisionalPage.initializationPromise;
   }
 
   onProvisionalLoadCommitted(session: WKSession) {

src/webkit/wkPageProxy.ts

@@ -139,10 +139,13 @@ export class WKPageProxy {
     }
     if (targetInfo.isProvisional) {
       (session as any)[isPovisionalSymbol] = true;
-      if (this._wkPage)
-        this._wkPage.onProvisionalLoadStarted(session);
-      if (targetInfo.isPaused)
+      if (this._wkPage) {
+        const provisionalPageInitialized = this._wkPage.initializeProvisionalPage(session);
+        if (targetInfo.isPaused)
+          provisionalPageInitialized.then(() => this._resumeTarget(targetInfo.targetId));
+      } else if (targetInfo.isPaused) {
         this._resumeTarget(targetInfo.targetId);
+      }
     } else if (this._pagePromise) {
       assert(!this._pagePausedOnStart);
       // This is the first time page target is created, will resume

src/webkit/wkProvisionalPage.ts

@@ -24,6 +24,7 @@ export class WKProvisionalPage {
   private readonly _wkPage: WKPage;
   private _sessionListeners: RegisteredListener[] = [];
   private _mainFrameId: string | null = null;
+  readonly initializationPromise: Promise<void>;
 
   constructor(session: WKSession, page: WKPage) {
     this._session = session;
@@ -47,7 +48,7 @@ export class WKProvisionalPage {
       helper.addEventListener(session, 'Network.loadingFailed', overrideFrameId(e => wkPage._onLoadingFailed(e))),
     ];
 
-    this._wkPage._initializeSession(session, ({frameTree}) => this._handleFrameTree(frameTree));
+    this.initializationPromise = this._wkPage._initializeSession(session, ({frameTree}) => this._handleFrameTree(frameTree));
   }
 
   dispose() {