Provide more context on infinite recursion in jest.runAllTimers

[ForbesLindesay]

Do you want to request a feature or report a bug?

Feature

What is the current behavior?

If you have an infinite loop of timers and run jest.runAllTimers(), you get the following error:

Ran 100000 timers, and there are still more! Assuming we've hit an infinite recursion and bailing out...

This doesn't really give me any context as to where these timers are. It's fine if the mistake was running jest.runAllTimers() but not if the mistake was having an infinite loop of timers.

What is the expected behavior?

What I would like to see is an error message that looks like the following:

Ran 100000 timers, and there are still more! Assuming we've hit an infinite recursion and bailing out.  The following timers are still pending:

setTimeout
  at someFn (some-file.js:15)
  at someOtherFn (some-other-file.js:17)

setImmediate
  at someFn (some-file.js:16)

i.e. for each pending timer, show what created the timer, and the stack trace at the time the tiemrs were created. This shouldn't affect existing performance too badly because the stack traces would only need to be gathered on the final run whenw e know we're about to report the infinite loop. Because we've already run it 1000 times, any legitimate timers should also already have finished running, which is convenient.

[thymikee]

I like the idea. Would you be willing to send a PR with the implementation?

[gagyibenedek]

I am willing to look into it, if this is still relevant. Is it? :)

[thymikee]

Yup, up for grabs!

[SimenB]

It would make more sense to provide this to Lolex as we will (at least most likely) migrate to it (see #5171). If you really want to, go ahead of course, it'll be useful either way :)

[SimenB]

I've opened up sinonjs/fake-timers#230

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