`Error: Generator is already running` when no callback provided about co

[jonathanong]

HAHAHA i figured it out. basically, we've got

try {
  ret.value.call(ctx, next);
} catch (e) {
  setImmediate(function(){
    next(e);
  })
}

but because next(e) itself throws if there's no done defined, it'll be recaught and re-thrown at gen.next(throw). the solution is that we always have to do setImmediate(function() {next(e)}).

try {
  ret.value.call(ctx, function(){
    var args = arguments;
    setImmediate(function(){
      next.apply(ctx, args);
    })
  })
} catch (err) {
  setImmediate(function(){
    next(err);
  })
}

however, i feel like this will still fail on the following case since we don't check that next is called twice:

co(function* () {
  yield function (done) {
    done(new Error())
    throw new Error()
  }
})

@visionmedia are you okay with adding setImmediate usage? it's either that or tell people never to yield synchronous functions, which isn't always obvious like yielding a generator. we could also use process.nextTick when available for performance.

[jonathanong]

hi, can you check that this branch works? maybe add a few test cases: #50

[vkurchatkin]

Yep, everything looks ok. Good job!

[jonathanong]

okay the PRs are merged. can you check that it works properly in master?

[vkurchatkin]

Everything seems to work.

[yyrdl]

you can check if it is necessary to setImmediate. In other words ，you can check if the func after yield is
asynchronous.