fix: use WeakRef for tracked handles

CHANGELOG.md

@@ -48,6 +48,7 @@
 - `[jest-config]` [**BREAKING**] Change default file extension order by moving json behind ts and tsx ([10572](https://github.com/facebook/jest/pull/10572))
 - `[jest-console]` `console.dir` now respects the second argument correctly ([#10638](https://github.com/facebook/jest/pull/10638))
 - `[jest-core]` Don't report PerformanceObserver as open handle ([#11123](https://github.com/facebook/jest/pull/11123))
+- `[jest-core]` Use `WeakRef` to hold timers when detecting open handles ([#11277](https://github.com/facebook/jest/pull/11277))
 - `[jest-each]` [**BREAKING**] Ignore excess words in headings ([#8766](https://github.com/facebook/jest/pull/8766))
 - `[jest-environment]` [**BREAKING**] Drop support for `runScript` for test environments ([#11155](https://github.com/facebook/jest/pull/11155))
 - `[jest-environment-jsdom]` Use inner realm’s `ArrayBuffer` constructor ([#10885](https://github.com/facebook/jest/pull/10885))

packages/jest-core/src/cli/index.ts

@@ -32,7 +32,7 @@ import watch from '../watch';
 
 const {print: preRunMessagePrint} = preRunMessage;
 
-type OnCompleteCallback = (results: AggregatedResult) => void;
+type OnCompleteCallback = (results: AggregatedResult) => void | undefined;
 
 export async function runCLI(
   argv: Config.Argv,
@@ -89,7 +89,9 @@ export async function runCLI(
     configsOfProjectsToRun,
     hasDeprecationWarnings,
     outputStream,
-    r => (results = r),
+    r => {
+      results = r;
+    },
   );
 
   if (argv.watch || argv.watchAll) {

packages/jest-core/src/collectHandles.ts

@@ -13,6 +13,8 @@ import type {Config} from '@jest/types';
 import {formatExecError} from 'jest-message-util';
 import {ErrorWithStack} from 'jest-util';
 
+export type HandleCollectionResult = () => Array<Error>;
+
 function stackIsFromUser(stack: string) {
   // Either the test file, or something required by it
   if (stack.includes('Runtime.requireModule')) {
@@ -37,13 +39,15 @@ function stackIsFromUser(stack: string) {
 
 const alwaysActive = () => true;
 
+const hasWeakRef = typeof WeakRef === 'function';
+
 // Inspired by https://github.com/mafintosh/why-is-node-running/blob/master/index.js
 // Extracted as we want to format the result ourselves
-export default function collectHandles(): () => Array<Error> {
-  const activeHandles: Map<
+export default function collectHandles(): HandleCollectionResult {
+  const activeHandles = new Map<
     number,
     {error: Error; isActive: () => boolean}
-  > = new Map();
+  >();
   const hook = asyncHooks.createHook({
     destroy(asyncId) {
       activeHandles.delete(asyncId);
@@ -68,10 +72,18 @@ export default function collectHandles(): () => Array<Error> {
         let isActive: () => boolean;
 
         if (type === 'Timeout' || type === 'Immediate') {
+          // Timer that supports hasRef (Node v11+)
           if ('hasRef' in resource) {
-            // Timer that supports hasRef (Node v11+)
-            // @ts-expect-error: doesn't exist in v10 typings
-            isActive = resource.hasRef.bind(resource);
+            if (hasWeakRef) {
+              const ref = new WeakRef(resource);
+              isActive = () => {
+                // @ts-expect-error: doesn't exist in v10 typings
+                return ref.deref()?.hasRef() ?? false;
+              };
+            } else {
+              // @ts-expect-error: doesn't exist in v10 typings
+              isActive = resource.hasRef.bind(resource);
+            }
           } else {
             // Timer that doesn't support hasRef
             isActive = alwaysActive;
@@ -88,7 +100,7 @@ export default function collectHandles(): () => Array<Error> {
 
   hook.enable();
 
-  return (): Array<Error> => {
+  return () => {
     hook.disable();
 
     // Get errors for every async resource still referenced at this moment

packages/jest-core/src/runJest.ts

@@ -26,7 +26,7 @@ import type FailedTestsCache from './FailedTestsCache';
 import SearchSource from './SearchSource';
 import TestScheduler, {TestSchedulerContext} from './TestScheduler';
 import type TestWatcher from './TestWatcher';
-import collectNodeHandles from './collectHandles';
+import collectNodeHandles, {HandleCollectionResult} from './collectHandles';
 import getNoTestsFoundMessage from './getNoTestsFoundMessage';
 import runGlobalHook from './runGlobalHook';
 import type {Filter, TestRunData} from './types';
@@ -70,7 +70,7 @@ type ProcessResultOptions = Pick<
   Config.GlobalConfig,
   'json' | 'outputFile' | 'testResultsProcessor'
 > & {
-  collectHandles?: () => Array<Error>;
+  collectHandles?: HandleCollectionResult;
   onComplete?: (result: AggregatedResult) => void;
   outputStream: NodeJS.WriteStream;
 };
@@ -111,7 +111,7 @@ const processResults = (
     }
   }
 
-  return onComplete && onComplete(runResults);
+  onComplete?.(runResults);
 };
 
 const testSchedulerContext: TestSchedulerContext = {
@@ -278,7 +278,7 @@ export default async function runJest({
     await runGlobalHook({allTests, globalConfig, moduleName: 'globalTeardown'});
   }
 
-  await processResults(results, {
+  processResults(results, {
     collectHandles,
     json: globalConfig.json,
     onComplete,