peter/src/utils/defer-promise.js

Peter Test Framework

/**
 *  @file       src/utils/defer-promise.js
 *  @author     Ryan Rossiter, ryan@kingsds.network
 *  @date       July 2020
 *
 *  This utility function will wrap a promise to prevent it from
 *  throwing an UnhandledPromiseRejectionWarning, and return a function
 *  so that the promise can be handled later.
 */

/**
 * @template T
 * @callback DeferPromiseCallback
 * @returns {Promise<T>}
 */

/**
 * @template T
 * @param {Promise<T>} promise 
 * @returns {DeferPromiseCallback<T>}
 */
module.exports = function deferPromise(promise) { 
  let threw = false;
  let result = undefined;

  let handledPromise = promise.then(
    (res) => (result = res),
    (err) => {
      threw = true;
      result = err;
    }
  );

  return async () => {
    await handledPromise;

    if (threw) throw result;
    else return result;
  }
}