test-util-promisify.js

'use strict';
// Flags: --expose-internals
const common = require('../common');
const assert = require('assert');
const fs = require('fs');
const vm = require('vm');
const { promisify } = require('util');
const { customPromisifyArgs } = require('internal/util');

common.crashOnUnhandledRejection();

const stat = promisify(fs.stat);

{
  const promise = stat(__filename);
  assert(promise instanceof Promise);
  promise.then(common.mustCall((value) => {
    assert.deepStrictEqual(value, fs.statSync(__filename));
  }));
}

{
  const promise = stat('/dontexist');
  promise.catch(common.mustCall((error) => {
    assert(error.message.includes('ENOENT: no such file or directory, stat'));
  }));
}

{
  function fn() {}
  function promisifedFn() {}
  fn[promisify.custom] = promisifedFn;
  assert.strictEqual(promisify(fn), promisifedFn);
  assert.strictEqual(promisify(promisify(fn)), promisifedFn);
}

{
  function fn() {}
  fn[promisify.custom] = 42;
  assert.throws(
      () => promisify(fn),
      (err) => err instanceof TypeError &&
                err.message === 'The [util.promisify.custom] property must ' +
                                'be a function');
}

{
  const firstValue = 5;
  const secondValue = 17;

  function fn(callback) {
    callback(null, firstValue, secondValue);
  }

  fn[customPromisifyArgs] = ['first', 'second'];

  promisify(fn)().then(common.mustCall((obj) => {
    assert.deepStrictEqual(obj, {first: firstValue, second: secondValue});
  }));
}

{
  const fn = vm.runInNewContext('(function() {})');
  assert.notStrictEqual(Object.getPrototypeOf(promisify(fn)),
                        Function.prototype);
}

{
  function fn(callback) {
    callback(null, 'foo', 'bar');
  }
  promisify(fn)().then(common.mustCall((value) => {
    assert.deepStrictEqual(value, 'foo');
  }));
}

{
  function fn(callback) {
    callback(null);
  }
  promisify(fn)().then(common.mustCall((value) => {
    assert.strictEqual(value, undefined);
  }));
}

{
  function fn(callback) {
    callback();
  }
  promisify(fn)().then(common.mustCall((value) => {
    assert.strictEqual(value, undefined);
  }));
}

{
  function fn(err, val, callback) {
    callback(err, val);
  }
  promisify(fn)(null, 42).then(common.mustCall((value) => {
    assert.strictEqual(value, 42);
  }));
}

{
  function fn(err, val, callback) {
    callback(err, val);
  }
  promisify(fn)(new Error('oops'), null).catch(common.mustCall((err) => {
    assert.strictEqual(err.message, 'oops');
  }));
}

{
  function fn(err, val, callback) {
    callback(err, val);
  }

  (async () => {
    const value = await promisify(fn)(null, 42);
    assert.strictEqual(value, 42);
  })();
}

{
  const o = {};
  const fn = promisify(function(cb) {

    cb(null, this === o);
  });

  o.fn = fn;

  o.fn().then(common.mustCall(function(val) {
    assert(val);
  }));
}

{
  const err = new Error('Should not have called the callback with the error.');
  const stack = err.stack;

  const fn = promisify(function(cb) {
    cb(null);
    cb(err);
  });

  (async () => {
    await fn();
    await Promise.resolve();
    return assert.strictEqual(stack, err.stack);
  })();
}

{
  function c() { }
  const a = promisify(function() { });
  const b = promisify(a);
  assert.notStrictEqual(c, a);
  assert.strictEqual(a, b);
}

{
  let errToThrow;
  const thrower = promisify(function(a, b, c, cb) {
    errToThrow = new Error();
    throw errToThrow;
  });
  thrower(1, 2, 3)
    .then(assert.fail)
    .then(assert.fail, (e) => assert.strictEqual(e, errToThrow));
}

{
  const err = new Error();

  const a = promisify((cb) => cb(err))();
  const b = promisify(() => { throw err; })();

  Promise.all([
    a.then(assert.fail, function(e) {
      assert.strictEqual(err, e);
    }),
    b.then(assert.fail, function(e) {
      assert.strictEqual(err, e);
    })
  ]);
}