Process yield undefined about co HOT 7 CLOSED

maybe try this

yield x() || 'whoops'

from co.

Could you tell me why you need yield undefined instead of Promise.resolve(undefined)?
Frequently used? It would be nice if there're an example.

I'm curios about this case.

from co.

I'm going to vote no on this suggestion. yield undefined is usually an error, and I would want this to throw.

from co.

@ifsnow

function asyncFn(user) {
  if(!user) return;
  const userName = user.name + ' ' + user.lastname;
  if(userName != 'Alex Wolf') return;
  user.fullname = userName;

  return use(user); // returning promise
}

function* main() {
  const user = yield asyncFn(); // error!
}

from co.

@JWo1F I think you can solve it by fixing your code without co's help.

Here is the code I tested.

function use(user) {
    return new Promise(function (resolve, reject) {
        return resolve(user);
    });
};

function asyncFn(user) {
    if(!user || user.name !== 'Alex' || user.lastname !== 'Wolf') {
        return Promise.resolve(undefined);
    }

    user.fullname = user.name + ' ' + user.lastname;

    return use(user);
};

co(function *() {
    const user = {
        name : 'Alex',
        lastname : 'Wolf'
    };

    const processedUser = yield asyncFn(user);
});

I hope this helps.

from co.

@ifsnow Last I checked that's more code. I just hit the need for this tonight. I have an entire module abstraction that was not originally built for yielding. I'd like to start introducing the concept of generators into some of those modules.

Without being able to yield undefined I need to restructure/refactor the entire module abstraction across all modules because some modules manipulate data structures but don't actually return anything. Whereas if yield undefined was supported I could very easily introduce generators without restructuring the entire code base.

from co.

@clearly It seems like co doesn't be maintained well. so, I added the way to skip errors for unsupported objects to co-booster that I made. co-booster is a performance tuning version of co. If you're already using co, you can make it work more faster by changing only the module. It's fully compatible with co.

Here is co-booster

If you set skipUnsupportError, co will no longer throw errors for unsupported objects.

co.skipUnsupportError = true;

co(function* () {
  yield undefined;
});

I hope this helps.

from co.