api(websocket): do not send websocket frames without a listener (#4361)

Once user adds 'websocket' listener, we start sending the frames
for all websockets on the page.

src/client/page.ts

@@ -577,19 +577,19 @@ export class Page extends ChannelOwner<channels.PageChannel, channels.PageInitia
   }
 
   on(event: string | symbol, listener: Listener): this {
-    if (event === Events.Page.FileChooser) {
+    if (event === Events.Page.FileChooser && !this.listenerCount(event))
-      if (!this.listenerCount(event))
       this._channel.setFileChooserInterceptedNoReply({ intercepted: true });
-    }
+    if (event === Events.Page.WebSocket && !this.listenerCount(event))
+      this._channel.setWebSocketFramesReportingEnabledNoReply({ enabled: true });
     super.on(event, listener);
     return this;
   }
 
   addListener(event: string | symbol, listener: Listener): this {
-    if (event === Events.Page.FileChooser) {
+    if (event === Events.Page.FileChooser && !this.listenerCount(event))
-      if (!this.listenerCount(event))
       this._channel.setFileChooserInterceptedNoReply({ intercepted: true });
-    }
+    if (event === Events.Page.WebSocket && !this.listenerCount(event))
+      this._channel.setWebSocketFramesReportingEnabledNoReply({ enabled: true });
     super.addListener(event, listener);
     return this;
   }
@@ -598,6 +598,9 @@ export class Page extends ChannelOwner<channels.PageChannel, channels.PageInitia
     super.off(event, listener);
     if (event === Events.Page.FileChooser && !this.listenerCount(event))
       this._channel.setFileChooserInterceptedNoReply({ intercepted: false });
+    // Note: we do not stop reporting web socket frames, since
+    // user might not listen to 'websocket' anymore, but still have
+    // a functioning WebSocket object.
     return this;
   }
 
@@ -605,6 +608,9 @@ export class Page extends ChannelOwner<channels.PageChannel, channels.PageInitia
     super.removeListener(event, listener);
     if (event === Events.Page.FileChooser && !this.listenerCount(event))
       this._channel.setFileChooserInterceptedNoReply({ intercepted: false });
+    // Note: we do not stop reporting web socket frames, since
+    // user might not listen to 'websocket' anymore, but still have
+    // a functioning WebSocket object.
     return this;
   }
 

src/dispatchers/pageDispatcher.ts

@@ -158,6 +158,10 @@ export class PageDispatcher extends Dispatcher<Page, channels.PageInitializer> i
     await this._page._setFileChooserIntercepted(params.intercepted);
   }
 
+  async setWebSocketFramesReportingEnabledNoReply(params: channels.PageSetWebSocketFramesReportingEnabledNoReplyParams): Promise<void> {
+    this._page._setWebSocketFramesReportingEnabled(params.enabled);
+  }
+
   async keyboardDown(params: channels.PageKeyboardDownParams): Promise<void> {
     await this._page.keyboard.down(params.key);
   }

src/protocol/channels.ts

@@ -727,6 +727,7 @@ export interface PageChannel extends Channel {
   setDefaultNavigationTimeoutNoReply(params: PageSetDefaultNavigationTimeoutNoReplyParams, metadata?: Metadata): Promise<PageSetDefaultNavigationTimeoutNoReplyResult>;
   setDefaultTimeoutNoReply(params: PageSetDefaultTimeoutNoReplyParams, metadata?: Metadata): Promise<PageSetDefaultTimeoutNoReplyResult>;
   setFileChooserInterceptedNoReply(params: PageSetFileChooserInterceptedNoReplyParams, metadata?: Metadata): Promise<PageSetFileChooserInterceptedNoReplyResult>;
+  setWebSocketFramesReportingEnabledNoReply(params: PageSetWebSocketFramesReportingEnabledNoReplyParams, metadata?: Metadata): Promise<PageSetWebSocketFramesReportingEnabledNoReplyResult>;
   addInitScript(params: PageAddInitScriptParams, metadata?: Metadata): Promise<PageAddInitScriptResult>;
   close(params: PageCloseParams, metadata?: Metadata): Promise<PageCloseResult>;
   emulateMedia(params: PageEmulateMediaParams, metadata?: Metadata): Promise<PageEmulateMediaResult>;
@@ -838,6 +839,13 @@ export type PageSetFileChooserInterceptedNoReplyOptions = {
 
 };
 export type PageSetFileChooserInterceptedNoReplyResult = void;
+export type PageSetWebSocketFramesReportingEnabledNoReplyParams = {
+  enabled: boolean,
+};
+export type PageSetWebSocketFramesReportingEnabledNoReplyOptions = {
+
+};
+export type PageSetWebSocketFramesReportingEnabledNoReplyResult = void;
 export type PageAddInitScriptParams = {
   source: string,
 };

src/protocol/protocol.yml

@@ -624,6 +624,10 @@ Page:
       parameters:
         intercepted: boolean
 
+    setWebSocketFramesReportingEnabledNoReply:
+      parameters:
+        enabled: boolean
+
     addInitScript:
       parameters:
         source: string

src/protocol/validator.ts

@@ -330,6 +330,9 @@ export function createScheme(tChannel: (name: string) => Validator): Scheme {
   scheme.PageSetFileChooserInterceptedNoReplyParams = tObject({
     intercepted: tBoolean,
   });
+  scheme.PageSetWebSocketFramesReportingEnabledNoReplyParams = tObject({
+    enabled: tBoolean,
+  });
   scheme.PageAddInitScriptParams = tObject({
     source: tString,
   });

src/server/frames.ts

@@ -359,12 +359,16 @@ export class FrameManager {
   }
 
   onWebSocketFrameSent(requestId: string, opcode: number, data: string) {
+    if (!this._page._webSocketFramesReportingEnabled)
+      return;
     const ws = this._webSockets.get(requestId);
     if (ws)
       ws.frameSent(opcode, data);
   }
 
   webSocketFrameReceived(requestId: string, opcode: number, data: string) {
+    if (!this._page._webSocketFramesReportingEnabled)
+      return;
     const ws = this._webSockets.get(requestId);
     if (ws)
       ws.frameReceived(opcode, data);

src/server/page.ts

@@ -145,6 +145,7 @@ export class Page extends EventEmitter {
   _ownedContext: BrowserContext | undefined;
   readonly selectors: Selectors;
   _video: Video | null = null;
+  _webSocketFramesReportingEnabled = false;
 
   constructor(delegate: PageDelegate, browserContext: BrowserContext) {
     super();
@@ -419,6 +420,10 @@ export class Page extends EventEmitter {
     await this._delegate.setFileChooserIntercepted(enabled);
   }
 
+  _setWebSocketFramesReportingEnabled(enabled: boolean) {
+    this._webSocketFramesReportingEnabled = enabled;
+  }
+
   videoStarted(video: Video) {
     this._video = video;
     this.emit(Page.Events.VideoStarted, video);