Loopback support for async/await

Question

I'm using loopback 3 to build a REST service, and I want to use the async/await instead of having to use the callbacks. So instead of doing that:

MyModel.myFunction = (callback) => {
  MyModel.find({where: {id: 2}}, (e, data) => {
    if (e) return callback(e);
    callback(null, data);
  });
};

I would greatly prefer to do:

MyModel.myFunction = async (callback) => {
  try {
    const data = await MyModel.find({where: {id: 2}});
    callback(null, data);
  } catch (e) {
    console.error(e);
    callback(e);
  }
};

The callback approach works perfectly - async/await however gives numerous errors:

• UnhandledPromiseRejectionWarning: Error: Callback was already called.
• UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch().

What's wrong? I cannot get through this issue.

Answer 1

Looks like I was simply mixing two concepts, this is the solution:

MyModel.myFunction = async (callback) => {
  try {
    const data = await MyModel.find({where: {id: 2}});
    return Promise.resolve(data);
  } catch (e) {
    console.error(e);
    return Promise.reject(e);
  }
};

Answer 2

Some refactoring:

MyModel.myFunction = async () => {
  try {
    const data = await MyModel.find({where: {id: 2}});
    return data; // it's enough as the async means it returns a promise
  } catch (e) {
    console.error(e);
    throw e;
  }
};

This one in case if you don't need to log an error (loopback error handler logs it instead of you):

MyModel.myFunction = async () => {
  return MyModel.find({where: {id: 2}});
};