[I am sorry about this] Jest bug when using `MockScope.delay`

Bug Description

I want to preface that using Jest was not my choice.

Reproducible By

import { MockAgent, setGlobalDispatcher, request } from 'undici'

const mockAgent = new MockAgent();
mockAgent.disableNetConnect();
setGlobalDispatcher(mockAgent);

const mockPool = mockAgent.get('http://localhost:3333');

mockPool.intercept({
	path: '/jest-bugs',
	method: 'GET'
}).reply(200, 'Hello').delay(100).times(2);

test('I wish this codebase used tap', async () => {
	const ac = new AbortController();
	setTimeout(() => ac.abort(), 5);
	const promise = request('http://localhost:3333/jest-bugs', {
		signal: ac.signal
	});

	await expect(promise).rejects.toThrowError('Request aborted');
}, 1000);

Expected Behavior

Logs & Screenshots

 PASS  __tests__/Jest.test.ts
  √ I wish this codebase used tap (16 ms)

----------|---------|----------|---------|---------|-------------------
File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
----------|---------|----------|---------|---------|-------------------
All files |       0 |        0 |       0 |       0 | 
----------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        1.187 s, estimated 2 s
Ran all test suites matching /__tests__\\Jest.test.ts/i.
node:async_hooks:202
        ReflectApply(fn, thisArg, args);
        ^

TypeError: Function.prototype.apply was called on null, which is a object and not a function
    at RequestHandler.runInAsyncScope (node:async_hooks:202:9)
    at RequestHandler.onHeaders (\node_modules\undici\lib\api\api-request.js:91:10)
    at handleReply (\node_modules\undici\lib\mock\mock-utils.js:200:13)
    at Timeout._onTimeout (\node_modules\undici\lib\mock\mock-utils.js:189:7)
    at listOnTimeout (node:internal/timers:559:17)
    at processTimers (node:internal/timers:502:7)

Node.js v17.8.0

Environment

Windows 10 Nodejs v17.8.0

Additional context

Even though the test passes, the CI still exits with exit code 1 and the workflow fails 😢

[KhafraDev]

Not that bad to debug really… much easier than I expected.

Somewhere an error occurs, triggering the onError callback; https://github.com/nodejs/undici/blob/f5d9a94e8771708a2d3654e412cb82404bf7cf4f/lib/api/api-request.js#L116 where err is

RequestAbortedError [AbortError]: Request aborted
          at abort (\undici\lib\api\abort-signal.js:12:18)
          at AbortSignal.self.<computed> (\undici\lib\api\abort-signal.js:32:5)
          at AbortSignal.[nodejs.internal.kHybridDispatch] (node:internal/event_target:643:20)
          at AbortSignal.dispatchEvent (node:internal/event_target:585:26)
          at abortSignal (node:internal/abort_controller:291:10)
          at AbortController.abort (node:internal/abort_controller:322:5)
          at Timeout._onTimeout (\undici\test\jest\jest.test.js:17:22)
          at listOnTimeout (node:internal/timers:559:17)
          at processTimers (node:internal/timers:502:7) {
        code: 'UND_ERR_ABORTED'
      }

      at RequestHandler.onError (lib/api/api-request.js:119:13)

The stack trace itself doesn’t mean much, it just shows that the request was successfully aborted (yay!).

Since callback exists, the statement runs, and sets the callback to null here; https://github.com/nodejs/undici/blob/f5d9a94e8771708a2d3654e412cb82404bf7cf4f/lib/api/api-request.js#L123

If the fix is just to add an if (callback !== null) { ... } then I am glad to make a PR, but I’m not really familiar with this section of the code and what [in]correct behavior looks like.

[mcollina]

My reading of this bug is that is a jest bug. It seems they are modifying the timers lists from the outside, causing this error in the async_hooks machinery.

I likely don’t have the time to debug this 😦.