chore: make TestWatcher extend emittery

packages/jest-core/package.json

@@ -13,6 +13,7 @@
     "@types/node": "*",
     "ansi-escapes": "^4.2.1",
     "chalk": "^4.0.0",
+    "emittery": "^0.7.1",
     "exit": "^0.1.2",
     "graceful-fs": "^4.2.4",
     "jest-changed-files": "^26.1.0",

packages/jest-core/src/TestScheduler.ts

@@ -426,15 +426,15 @@ export default class TestScheduler {
       aggregatedResults.numFailedTests >= this._globalConfig.bail
     ) {
       if (watcher.isWatchMode()) {
-        watcher.setState({interrupted: true});
-      } else {
-        const failureExit = () => exit(1);
-
-        return this._dispatcher
-          .onRunComplete(contexts, aggregatedResults)
-          .then(failureExit)
-          .catch(failureExit);
+        return watcher.setState({interrupted: true});
       }
+
+      const failureExit = () => exit(1);
+
+      return this._dispatcher
+        .onRunComplete(contexts, aggregatedResults)
+        .then(failureExit)
+        .catch(failureExit);
     }
     return Promise.resolve();
   }

packages/jest-core/src/TestWatcher.ts

@@ -5,13 +5,13 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import {EventEmitter} from 'events';
+import emittery = require('emittery');
 
 type State = {
   interrupted: boolean;
 };
 
-export default class TestWatcher extends EventEmitter {
+export default class TestWatcher extends emittery.Typed<{change: State}> {
   state: State;
   private _isWatchMode: boolean;
 
@@ -21,9 +21,9 @@ export default class TestWatcher extends EventEmitter {
     this._isWatchMode = isWatchMode;
   }
 
-  setState(state: State): void {
+  async setState(state: State): Promise<void> {
     Object.assign(this.state, state);
-    this.emit('change', this.state);
+    await this.emit('change', this.state);
   }
 
   isInterrupted(): boolean {

packages/jest-runner/src/index.ts

@@ -25,7 +25,6 @@ import type {
   TestRunnerContext as JestTestRunnerContext,
   TestRunnerOptions as JestTestRunnerOptions,
   TestWatcher as JestTestWatcher,
-  WatcherState,
 } from './types';
 
 const TEST_WORKER_PATH = require.resolve('./testWorker');
@@ -243,7 +242,7 @@ class TestRunner {
     };
 
     const onInterrupt = new Promise((_, reject) => {
-      watcher.on('change', (state: WatcherState) => {
+      watcher.on('change', state => {
         if (state.interrupted) {
           reject(new CancelRun());
         }

packages/jest-runner/src/types.ts

@@ -5,7 +5,7 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import type {EventEmitter} from 'events';
+import type {Typed as EmitteryTyped} from 'emittery';
 import type {Config} from '@jest/types';
 import type {
   AssertionResult,
@@ -79,10 +79,8 @@ export type TestRunnerSerializedContext = {
 };
 
 // TODO: Should live in `@jest/core` or `jest-watcher`
-export type WatcherState = {
-  interrupted: boolean;
-};
-export interface TestWatcher extends EventEmitter {
+type WatcherState = {interrupted: boolean};
+export interface TestWatcher extends EmitteryTyped<{change: WatcherState}> {
   state: WatcherState;
   setState(state: WatcherState): void;
   isInterrupted(): boolean;

yarn.lock

@@ -1708,6 +1708,7 @@ __metadata:
     "@types/rimraf": ^3.0.0
     ansi-escapes: ^4.2.1
     chalk: ^4.0.0
+    emittery: ^0.7.1
     exit: ^0.1.2
     graceful-fs: ^4.2.4
     jest-changed-files: ^26.1.0