Making async.forever run... forever =)

[rdegges]

Previously, if async.forever was called, since it wasn't using setImmediate --
the max call stack size would be exceeded rather quickly.

This fix introduces setImmediate behavior to prevent user-generated tasks from
starving the event loop of resources.

Fixes #437.

[aearly]

That will happen if the function you pass to forever isn't async. Have you tried adding a async.nextTick(callback); in that function?

[rdegges]

Hey @aearly -- unfortunately that doesn't work :( take this code snippet for instance:

var async = require('async');

var i = 0;
async.forever(
  function(next) {
    console.log('hi', i);
    i++;
    async.nextTick(next);
  }, function() { }
);

If you run that you'll get:

(node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.
(node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.
(node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.
(node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.
(node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.
(node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.
(node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.
(node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.
(node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.
(node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.
(node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.
(node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.
(node) warning: Recursive process.nextTick detected. This will break in the next version of node. Please use setImmediate for recursive deferral.

RangeError: Maximum call stack size exceeded

[aearly]

Then do what it says -- try setImmediate instead.

[rdegges]

That's what I did -- that's also what the PR changes ^^

It makes sense to me to merge this in -- this way the behavior is guaranteed to run as expected for developers.

If you think it shouldn't -- feel free to close. Sorry for the confusion.