refactor: add TargetEventEmitter abstraction for Browser/BrowserContext

Extract a TargetEventEmitter interface and asTargetEmitter() helper to
unify Browser and BrowserContext target event handling. This enables
PageCollector and UniverseManager to work with both types without
type-specific branching.

Author: RobertWsp

package-lock.json

@@ -6,6 +6,7 @@
 
 import {PuppeteerDevToolsConnection} from './DevToolsConnectionAdapter.js';
 import {Mutex} from './Mutex.js';
+import type {TargetEventEmitter} from './PageCollector.js';
 import {DevTools} from './third_party/index.js';
 import type {
   Browser,
@@ -108,15 +109,15 @@ export interface TargetUniverse {
 export type TargetUniverseFactoryFn = (page: Page) => Promise<TargetUniverse>;
 
 export class UniverseManager {
-  readonly #browser: Browser;
+  readonly #browser: TargetEventEmitter;
   readonly #createUniverseFor: TargetUniverseFactoryFn;
   readonly #universes = new WeakMap<Page, TargetUniverse>();
 
   /** Guard access to #universes so we don't create unnecessary universes */
   readonly #mutex = new Mutex();
 
   constructor(
-    browser: Browser,
+    browser: TargetEventEmitter,
     factory: TargetUniverseFactoryFn = DEFAULT_FACTORY,
   ) {
     this.#browser = browser;

src/DevtoolsUtils.ts

@@ -15,13 +15,32 @@ import type {
 import {DevTools} from './third_party/index.js';
 import {
   type Browser,
+  type BrowserContext,
   type Frame,
   type Handler,
   type HTTPRequest,
   type Page,
   type PageEvents as PuppeteerPageEvents,
 } from './third_party/index.js';
 
+/**
+ * Common interface for Browser and BrowserContext target events.
+ * Both Browser and BrowserContext structurally satisfy this interface,
+ * enabling PageCollector and UniverseManager to work with either.
+ */
+export interface TargetEventEmitter {
+  on(type: 'targetcreated', handler: (target: Target) => void): unknown;
+  on(type: 'targetdestroyed', handler: (target: Target) => void): unknown;
+  off(type: 'targetcreated', handler: (target: Target) => void): unknown;
+  off(type: 'targetdestroyed', handler: (target: Target) => void): unknown;
+}
+
+export function asTargetEmitter(
+  source: Browser | BrowserContext | TargetEventEmitter,
+): TargetEventEmitter {
+  return source as unknown as TargetEventEmitter;
+}
+
 export class UncaughtError {
   readonly details: Protocol.Runtime.ExceptionDetails;
   readonly targetId: string;
@@ -57,7 +76,7 @@ type WithSymbolId<T> = T & {
 };
 
 export class PageCollector<T> {
-  #browser: Browser;
+  #browser: TargetEventEmitter;
   #listenersInitializer: (
     collector: (item: T) => void,
   ) => ListenerMap<PageEvents>;
@@ -72,7 +91,7 @@ export class PageCollector<T> {
   protected storage = new WeakMap<Page, Array<Array<WithSymbolId<T>>>>();
 
   constructor(
-    browser: Browser,
+    browser: TargetEventEmitter,
     listeners: (collector: (item: T) => void) => ListenerMap<PageEvents>,
   ) {
     this.#browser = browser;
@@ -373,7 +392,7 @@ class PageEventSubscriber {
 
 export class NetworkCollector extends PageCollector<HTTPRequest> {
   constructor(
-    browser: Browser,
+    browser: TargetEventEmitter,
     listeners: (
       collector: (item: HTTPRequest) => void,
     ) => ListenerMap<PageEvents> = collect => {

src/PageCollector.ts

@@ -14,6 +14,7 @@ import {
   urlsEqual,
   UniverseManager,
 } from '../src/DevtoolsUtils.js';
+import {asTargetEmitter} from '../src/PageCollector.js';
 import {DevTools} from '../src/third_party/index.js';
 import type {Browser, Target} from '../src/third_party/index.js';
 
@@ -102,7 +103,7 @@ describe('UniverseManager', () => {
   it('calls the factory for existing pages', async () => {
     const browser = getMockBrowser();
     const factory = sinon.stub().resolves({});
-    const manager = new UniverseManager(browser, factory);
+    const manager = new UniverseManager(asTargetEmitter(browser), factory);
     await manager.init(await browser.pages());
 
     const page = (await browser.pages())[0];
@@ -115,7 +116,7 @@ describe('UniverseManager', () => {
     } as unknown as Browser;
     // eslint-disable-next-line @typescript-eslint/no-empty-function
     const factory = sinon.stub().returns(new Promise(() => {})); // Don't resolve.
-    const manager = new UniverseManager(browser, factory);
+    const manager = new UniverseManager(asTargetEmitter(browser), factory);
     await manager.init([]);
 
     sinon.assert.notCalled(factory);
@@ -135,7 +136,7 @@ describe('UniverseManager', () => {
 
   it('works with a real browser', async () => {
     await withBrowser(async (browser, page) => {
-      const manager = new UniverseManager(browser);
+      const manager = new UniverseManager(asTargetEmitter(browser));
       await manager.init([page]);
 
       assert.notStrictEqual(manager.get(page), null);
@@ -144,7 +145,7 @@ describe('UniverseManager', () => {
 
   it('ignores pauses', async () => {
     await withBrowser(async (browser, page) => {
-      const manager = new UniverseManager(browser);
+      const manager = new UniverseManager(asTargetEmitter(browser));
       await manager.init([page]);
       const targetUniverse = manager.get(page);
       assert.ok(targetUniverse);