Looks like Promise.mapSeries will iterate all items before return

According to the documentation:

The iterator won’t be called for an item until its previous item, and the promise returned by the iterator for that item are fulfilled.

But in my test, the given Iteratable will be called unconditional even there’s promise be rejected. This’s my test script (Bluebird v3.1.1):

var bluebird = require('bluebird');

var myIterable = {};
myIterable[Symbol.iterator] = function* () {
  console.log('Yield first item');
  yield bluebird.reject(new Error('first item rejected'));
  console.log('Yield second item');
  yield bluebird.resolve('some value');
};

bluebird.mapSeries(myIterable, i => i)
  .then(items => {
    console.log('Items:', items);
  })
  .catch(err => {
    console.log('Some error: %s', err.message);
  });

Expect output:

Yield first item
Some error: first item rejected

Actual output:

Yield first item
Yield second item
Some error: first item rejected

Point out me if I have any misunderstanding, thanks.

[petkaantonov]

var bluebird = require('bluebird');

var iterator = bluebird.coroutine(function* () {
  console.log('Yield first item');
  var a = yield bluebird.reject(new Error('first item rejected'));
  console.log('Yield second item');
  var b = yield bluebird.resolve('some value');
  return [a, b];
});

iterator().then(function(items) {

});

[xiaogaozi]

Very thankful for this example!