Pushing an empty task onto the queue in q.drain results in an infinite loop.

[hargasinski]

What version of async are you using? v3.2.3

Which environment did the issue occur in (Node/browser/Babel/Typescript version) node & browser

What did you do? Please include a minimal reproducible case illustrating issue.

const q = async.queue(() => {})
q.drain(() => { q.push([]) })
q.push([])

What did you expect to happen?
The queue doesn't schedule another drain call if one is running.

What was the actual result?
The queue goes into an infinite loop.

I'm not sure this is necessarily a bug as queue is working as specified - if an empty task is pushed and it's idle, it drains. I only noticed it because in the priorityQueue tests, we have a test for this case, see tests/priorityQueue#L52. With the changes in #1790, the priorityQueuebehaves the same way as queue and goes into an infinite loop. We could add a check that if a drain call is running, not to schedule another one similar to what we do with q._process. Thoughts?

[aearly]

Yes, lets add the extra check to avoid an infinite loop. There are cases where you could accidentally get into this state and crash your app.

[hargasinski]

Sounds good, I'll create a PR for it this week.