feat(jest-circus): Fail tests if a test takes a done callback and have return values

[SimenB]

Summary

Using both promises and the callback is confusing as we don't actually wait for the promise at all. People should prefer promises (async functions) for all async work anyways as propagation is handled for them.

Not sure of we wanna land this for 25 or not. It's potentially a pain to fix, although using https://github.com/jest-community/eslint-plugin-jest/blob/master/docs/rules/no-test-callback.md makes it somewhat easier.

Didn't bother adding this to jasmine as it has some internal Spec and our promisifying thing that confused me.

This also fixes the case where

test('foo', () => {
  return 'bar';
});

would fail due to the returned string, but

test('foo', cb => {
  cb();

  return 'bar';
});

would not

Test plan

e2e test added. Haven't ran this locally in case

[jeysal]

Nice

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.
Please note this issue tracker is not a help forum. We recommend using StackOverflow or our discord channel for questions.