fs.promises API is not working as in node

[fxdave]

Introduction

The fs library of node provides an experimental feature: the fs/promises which has the same functionality but with promises.

The bug

import {promises as fsp} from 'fs'
fsp.readFile(SOME_VALID_URL, { encoding: 'utf8' })

Considering the code above, the readFile has 2 parameters: the url and the options.
In theory, the parameter options is default to {encoding:null, flag:'r'}.
The problem is that the flag won't be default if I run this with electron-webpack. But working if I run the code with node (and with babel of course). So with electron-webpack I get an exception:

NodeError: The value "undefined" is invalid for option "flags"
    at stringToFlags (internal/fs/utils.js:253:9)
    at open (internal/fs/promises.js:198:34)
    at Object.readFile (internal/fs/promises.js:466:20)
   ...

The stack trace doesn't tell so much but there's a function in promises.js:

async function readFile(path, options) {
  options = getOptions(options, { flag: 'r' });

  if (path instanceof FileHandle)
    return readFileHandle(path, options);

  const fd = await open(path, options.flag, 0o666);
  return readFileHandle(fd, options).finally(fd.close.bind(fd));
}

I tested and the getOptions(options, { flag: 'r' }) is giving back the options without modifications. Which is right because of the definition of getOptions:

function getOptions(options, defaultOptions) {
  if (options === null || options === undefined ||
      typeof options === 'function') {
    return defaultOptions;
  }

  if (typeof options === 'string') {
    defaultOptions = util._extend({}, defaultOptions);
    defaultOptions.encoding = options;
    options = defaultOptions;
  } else if (typeof options !== 'object') {
    throw new ERR_INVALID_ARG_TYPE('options', ['string', 'Object'], options);
  }

  if (options.encoding !== 'buffer')
    assertEncoding(options.encoding);
  return options;
}

By then, I don't really understand why is it working without electron-webpack. But the node documentation says it is correct to give object into the options.
https://nodejs.org/api/fs.html#fs_fspromises_readfile_path_options

Possible workaround

import {promises as fsp} from 'fs'
fsp.readFile(SOME_VALID_URL, { encoding: 'utf8' , flag: 'r'})

[fxdave]

I think the problem is the webpack because the source is outdated, I got this from the debugger:

async function readFile(path, options) {
  options = getOptions(options, { flag: 'r' });

  if (path instanceof FileHandle)
    return readFileHandle(path, options);

  const fd = await open(path, options.flag, 0o666);
  return readFileHandle(fd, options).finally(fd.close.bind(fd));
}

This should be:

async function readFile(path, options) {
  options = getOptions(options, { flag: 'r' });
  const flag = options.flag || 'r';

  if (path instanceof FileHandle)
    return readFileHandle(path, options);

  const fd = await open(path, flag, 0o666);
  return readFileHandle(fd, options).finally(fd.close.bind(fd));
}

Is it possible?