valid-expect-in-promise doesn't work with Promise.all

[realityking]

I have a test case that relies on multiple promises being tested with Promise.all:

test('Resource loader: client usage', function () {
  expect.assertions(2);

  const quxLoader = ResourceLoader.create(['qux']);
  let promiseResolve;
  fetchResult = new Promise(resolve => promiseResolve = resolve);

  const promise1 = quxLoader.load();
  promise1.then(([x]) => expect(x.test).toBeTruthy());
  const promise2 = quxLoader.load();
  promise2.then(([x])  => expect(x.test).toBeTruthy());
  promiseResolve({test: true});

  return Promise.all([promise1, promise2]);
});

This causes the following eslint errors:

  68:3  error  Promise should be returned to test its fulfillment or rejection  jest/valid-expect-in-promise
  70:3  error  Promise should be returned to test its fulfillment or rejection  jest/valid-expect-in-promise

It'd be great if the rule would recognize Promise.all and considered it valid.

[SimenB]

You don't wait for them though - when you do .then you return a new promise (from promise1 and promise2) which you don't wait for.

const somePromise = Promise.resolve();

somePromise.then(() => Promise.reject('oh no'));

Promise.all([somePromise]).then(() => {
  console.log('this resolves');
});

// logs
// this resolves
// "Uncaught (in promise) oh no"

[realityking]

🤦‍♂️ Good catch!

But if I change things to consider the new promises, it still fails:

New code:

test('Resource loader: client usage', function () {
  expect.assertions(2);

  const quxLoader = ResourceLoader.create(['qux']);
  let promiseResolve;
  fetchResult = new Promise(resolve => promiseResolve = resolve);

  const promise1 = quxLoader.load()
    .then(([x]) => expect(x.test).toBeTruthy());
  const promise2 = quxLoader.load()
    .then(([x]) => expect(x.test).toBeTruthy());
  promiseResolve({test: true});

  return Promise.all([promise1, promise2]);
});

eslint report:

  67:9  error  Promise should be returned to test its fulfillment or rejection  jest/valid-expect-in-promise
  69:9  error  Promise should be returned to test its fulfillment or rejection  jest/valid-expect-in-promise

[SimenB]

Yeah, that's a bug 🙂 Doesn't seem like the rule handles Promise.all at all. PR welcome! 😀

[G-Rath]

For now I've decided that actually Promise.all shouldn't be allowed because it rejects as soon as one of the promises reject, which'll always happen if you've got expect since it throws, meaning at best you're creating a conditional expectation which is something we don't recommend anyway.

Instead, Promise.allSettled should be used to ensure all promises are fulfilled.

[github-actions]

🎉 This issue has been resolved in version 24.6.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[github-actions]

🎉 This issue has been resolved in version 25.0.0-next.6 🎉

The release is available on:

• npm package (@next dist-tag)
• GitHub release

Your semantic-release bot 📦🚀