Keeps resubmitting inputs to transformer until the corresponding outputs test successfully. May not preserve the input order.

Expectation on Transformer:

• Outputs a single value per input

Example Usage

var pull = require('pull-stream')
var stubborn = require('pull-stubborn')

pull(
  pull.count(3),
  stubborn(
    pull.map(function (x) { 
      return { 
        status: Math.random() * 10,
        input: x,
        result: x*x
      } 
    }),
    function tester (x, cb) {
      var success = x.status >= 5 // 50% chance of success
      if (success) 
        cb(true, x.result) // Return result
      else 
        cb(false, x.input) // Resubmit input
    }
  ),
  pull.collect(function (err, arr) {
    if (err) return console.error(err)
    arr.sort()       // Results may be out of order
    console.log(arr) // Prints 0,1,4,9
  })
)

stubborn(transformer/duplex, tester(x, cb)) returns another transformer/duplex

cb has the following signature cb(success, value). If success===true then value is passed downstream. Otherwise, value is submitted to transformer/duplex again as input. Each case may use a different value.