Evaluate how different ES6 generator runners (Q, Bluebird and Co) behaves with buggy code

nodejs_generator_runners.md

Evaluate how different ES6 generator runners (Q, Bluebird and Co) behaves with buggy code

• NodeJS v5.6.0
• q@1.4.1
• bluebird@3.3.1
• co@4.6.0

var Q = require('q');
var bluebird = require('bluebird');
var co = require('co');

// Offtopic. Generator fn as a solution to lazy collection as iterables
function* items() {
  yield 1;
  yield 2;
  yield 3;
}

// Generator fn as a solution to async function composition
function* sum() {
  var x = yield Promise.resolve(1);
  var y = yield Promise.resolve(2);
  var z = yield Promise.resolve(3);
  return x + y + z;
}

function* f() {
  var x = yield* sum();
  console.log('x ==', x);
}

Q.spawn(f);
bluebird.coroutine(f)();
co(f);

Buggy code #1

-function* f() {
+function f() {

bluebird, q

  var x = yield* sum();
          ^
ReferenceError: yield is not defined

co

Runs but nothing is printed

Buggy code #2

-function* sum() {
+function sum() {

bluebird, co, q

  var x = yield Promise.resolve(1);
                ^^^^^^^
SyntaxError: Unexpected identifier

Buggy code #3

- var x = yield* sum();
+ var x = yield sum();

bluebird

Unhandled rejection TypeError: A value [object Generator] was yielded that could not be treated as a promise

 See http://goo.gl/MqrFmX

co

TODO Check why buggy code works - by accident or it's intentional behavior 
x == 6

q

Invalid result: x is {} but 6 is expected