Add onFirstPause utility method

[nicolo-ribaudo]

See babel/babel#10507 (comment)

[loganfsmyth]

I think you can do what you want with something like this?

  async: function([item, cb], resolve, reject) {
    let completed = false;

    evaluateAsync(item, value => {
      completed = true;
      resolve(value);
    }, err => {
      completed = true;
      reject(value);
    });

    if (!completed) {
      cb();
    }
  },

or alternatively using the existing public API:

const runGenerator = gensync(function* (item) {
  return yield* item;
});

const onFirstPause = gensync({
  name: "onFirstPause",
  arity: 2,
  sync: function([item]) {
    return runGenerator.sync(item);
  },
  errback: function([item, firstPause], cb) {
    let completed = false;

    // Gensync calls `errback` callbacks synchronously if it can, even in the async case, if I remember right
    runGenerator.errback(item, (err, value) => {
      completed = true;
      cb(value);
    });

    if (!completed) {
      firstPause();
    }
  },
})

[nicolo-ribaudo]

Ok, I will try the second approach 👍

[nicolo-ribaudo]

babel/babel@cc2cfd7