Unable to resolve promise when using async await with babel and ES6 promise

Question

I have the following node app containing an async function, awaiting an ES6 promise.

async function test(id){
    try {
        let val = await Promise.resolve(id);
        console.log("val: " + val);
    } catch (error) {
        console.log("error: " + error);
    }
}

test(1);

Result = val: undefined

Expected result: val: 1

I use gulp-babel to compile this to ES5.

I have the following set within the gulp task:

.pipe(babel({ optional: ["es7.asyncFunctions"] }))

I am also requiring in 'babel/polyfill' after npm installing babel.

Transpiled code:

function test(id) {
var val;
return regeneratorRuntime.async(function test$(context$1$0) {
    while (1) switch (context$1$0.prev = context$1$0.next) {
        case 0:
            context$1$0.prev = 0;
            context$1$0.next = 3;
            return Promise.resolve(id);

        case 3:
            val = context$1$0.sent;

            console.log('val: ' + val);
            context$1$0.next = 10;
            break;

        case 7:
            context$1$0.prev = 7;
            context$1$0.t0 = context$1$0['catch'](0);

            console.log('error: ' + context$1$0.t0);

        case 10:
        case 'end':
            return context$1$0.stop();
    }
}, null, this, [[0, 7]]);
}

test(1);

Answer 1

You appear to be using a version of Babel prior to Babel version 5.5.0. Before this version, it was possible to have regenerator (a dependency of Babel) installed at a version less than 0.8.28, which is the first version where regenerator started supporting await Promise.resolve(value) (the code in your example).

Support was added in this commit on the regenerator side, and Babel upgraded to require at least the 0.8.28 release of regenerator with this commit.