source: frontend/node_modules/execa/lib/promise.js

'use strict';

const nativePromisePrototype = (async () => {})().constructor.prototype;
const descriptors = ['then', 'catch', 'finally'].map(property => [
        property,
        Reflect.getOwnPropertyDescriptor(nativePromisePrototype, property)
]);

// The return value is a mixin of `childProcess` and `Promise`
const mergePromise = (spawned, promise) => {
        for (const [property, descriptor] of descriptors) {
                // Starting the main `promise` is deferred to avoid consuming streams
                const value = typeof promise === 'function' ?
                        (...args) => Reflect.apply(descriptor.value, promise(), args) :
                        descriptor.value.bind(promise);

                Reflect.defineProperty(spawned, property, {...descriptor, value});
        }

        return spawned;
};

// Use promises instead of `child_process` events
const getSpawnedPromise = spawned => {
        return new Promise((resolve, reject) => {
                spawned.on('exit', (exitCode, signal) => {
                        resolve({exitCode, signal});
                });

                spawned.on('error', error => {
                        reject(error);
                });

                if (spawned.stdin) {
                        spawned.stdin.on('error', error => {
                                reject(error);
                        });
                }
        });
};

module.exports = {
        mergePromise,
        getSpawnedPromise
};