eachSeries with a nested async call results in maximum call stack size exceeded

[brainthinks]

What version of async are you using?

2.0.1

Which environment did the issue occur in (Node version/browser version)

Node 6.2.1
NPM 3.9.3

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

let counter = 2000;

async.eachSeries(
  new Array(counter),
  (item, cb) => {
    async.parallel([
      (pCb) => {
        console.log(counter--);
        pCb();
      },
    ], cb);
  },
  () => console.log('done')
);

What did you expect to happen?

I expected each of the iterations to occur, which would result in the last two console.log's being '1' and 'done'.

What was the actual result?

After fewer than 1000 iterations, I would receive this error:

RangeError: Maximum call stack size exceeded

When I reverted back to async 1.5.2, the above code worked as expected.

[clickclickonsal]

+1

[jhyman2]

+1

[megawac]

The reason this worked in async 1.5.2 is we ensured the callback was always called asynchronously in that version. In version 2 we removed this guard (see https://github.com/caolan/async/blob/master/intro.md#synchronous-iteration-functions)

So in your case to fix the script you can either use async.ensureAsync(cb) or async.setImmediate(cb) to work around the recursion issue:

var counter = 2000;

async.eachSeries(
  new Array(counter),
  (item, cb) => {
    async.parallel([
      (pCb) => {
        console.log(counter--);
        async.setImmediate(pCb);
      },
    ], cb);
  },
  () => console.log('done')
);