Ignore DNSCHANNEL when using --detectOpenHandles (#11470)

Author: Mr0grog

CHANGELOG.md

@@ -9,6 +9,7 @@
 ### Fixes
 
 - `[jest-circus, @jest/test-sequencer]` Remove dependency on `jest-runner` ([#11466](https://github.com/facebook/jest/pull/11466))
+- `[jest-core]` Do not warn about `DNSCHANNEL` handles when using the `--detectOpenHandles` option ([#11470](https://github.com/facebook/jest/pull/11470))
 - `[jest-runner]` Remove dependency on `jest-config` ([#11466](https://github.com/facebook/jest/pull/11466))
 - `[jest-worker]` Loosen engine requirement to `>= 10.13.0` ([#11451](https://github.com/facebook/jest/pull/11451))
 

e2e/__tests__/__snapshots__/detectOpenHandles.ts.snap

@@ -13,7 +13,7 @@ This usually means that there are asynchronous operations that weren't stopped i
 exports[`prints out info about open handlers 1`] = `
 Jest has detected the following 1 open handle potentially keeping Jest from exiting:
 
-  ●  DNSCHANNEL
+  ●  TCPSERVERWRAP
 
       12 | const app = new Server();
       13 |

packages/jest-core/src/__tests__/collectHandles.test.js

@@ -6,6 +6,7 @@
  *
  */
 
+import {promises as dns} from 'dns';
 import http from 'http';
 import {PerformanceObserver} from 'perf_hooks';
 import collectHandles from '../collectHandles';
@@ -38,6 +39,19 @@ describe('collectHandles', () => {
     obs.disconnect();
   });
 
+  it('should not collect the DNSCHANNEL open handle', async () => {
+    const handleCollector = collectHandles();
+
+    const resolver = new dns.Resolver();
+    resolver.getServers();
+
+    const openHandles = await handleCollector();
+
+    expect(openHandles).not.toContainEqual(
+      expect.objectContaining({message: 'DNSCHANNEL'}),
+    );
+  });
+
   it('should collect handles opened in test functions with `done` callbacks', done => {
     const handleCollector = collectHandles();
     const server = http.createServer((_, response) => response.end('ok'));

packages/jest-core/src/collectHandles.ts

@@ -62,12 +62,16 @@ export default function collectHandles(): HandleCollectionResult {
       triggerAsyncId,
       resource: {} | NodeJS.Timeout,
     ) {
+      // Skip resources that should not generally prevent the process from
+      // exiting, not last a meaningfully long time, or otherwise shouldn't be
+      // tracked.
       if (
         type === 'PROMISE' ||
         type === 'TIMERWRAP' ||
         type === 'ELDHISTOGRAM' ||
         type === 'PerformanceObserver' ||
-        type === 'RANDOMBYTESREQUEST'
+        type === 'RANDOMBYTESREQUEST' ||
+        type === 'DNSCHANNEL'
       ) {
         return;
       }