Detect hanging async operations

[cyco130]

Clear and concise description of the problem

As a developer using Vitest I want to be able to detect if an async operation that was started during a test case hasn't completed at the end of that test so that I can catch hanging promise bugs. I am willing to contribute a PR if there is interest.

Suggested solution

We could provide a --detect-async-leaks flag to turn on this type of detection. Node.js's builtin async_hooks module provides the necessary functionality

Alternative

Alternatively, we could make this the default and provide an option to turn it off.

Additional context

For example in Deno the following test fails with the message "Test case is leaking async ops":

Deno.test("hanging interval", () => {
  setInterval(() => {}, 1000);
});

This helped me catch a few particularly hard to find bugs in a streaming form data parser I was working on. Web streams are particularly prone to this type of error but there are many other cases where such detection would be useful.

Validations

• [X] Follow our Code of Conduct
• [X] Read the Contributing Guidelines.
• [X] Read the docs.
• [X] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[dsumac]

Do you have some feedbacks on this issue ?

[sheremet-va]

Sounds like a nice feature. We can probably extend runner somewhere here:

https://github.com/vitest-dev/vitest/blob/7006bb367494536e2ecf762a5636e509734e43e5/packages/vitest/src/runtime/runners/test.ts#L54

Since this is Node.js-only feature, we would need to extend this class in a separate file so as not to break browser runner which also relies on this class.

In Node.js it is imported here:

https://github.com/vitest-dev/vitest/blob/7006bb367494536e2ecf762a5636e509734e43e5/packages/vitest/src/runtime/runners/index.ts#L15

[tkrotoff]

Here a comparison with Jest (no CLI option or special config required):

import { test } from "vitest";

// Jest output: "ELIFECYCLE Test failed. See above for more details."
test("error after tests are done", () => {
  setTimeout(() => {
    throw new Error("after tests are done");
  }, 100);
});

// Jest output:
// "Jest did not exit one second after the test run has completed.
//  This usually means that there are asynchronous operations that weren't stopped in your tests.
//  Consider running Jest with `--detectOpenHandles` to troubleshoot this issue."
// "Jest has detected the following 1 open handle potentially keeping Jest from exiting: [...]"
test("open handles", () => {
  setInterval(() => {}, 100);
});

// Jest output: "Cannot log after tests are done. Did you forget to wait for something async in your test?"
test("console usage after tests are done", () => {
  setTimeout(() => {
    console.info("after tests are done");
  }, 100);
});

Vitest won't report any issue while all these tests fail with Jest (modulo this issue)

node:test & Mocha also detect those cases (without any particular CLI option or config)

[sheremet-va]

node:test & Mocha also detect those cases (without any particular CLI option or config)

Cannot confirm that this is true. In mocha I get the error "after tests are done" which does change processExit, but doesn't print any information about leaking. node:test just hangs for me (probably because of setInterval).

mocha

node:test (Node 20.11.0)