Nuxt/packages/webpack/src/utils/async-mfs.js

import MFS from 'memory-fs'
export default class AsyncMFS extends MFS {}

const syncRegex = /Sync$/

const propsToPromisify = Object.getOwnPropertyNames(MFS.prototype).filter(n => syncRegex.test(n))

for (const prop of propsToPromisify) {
  const asyncProp = prop.replace(syncRegex, '')
  const origAsync = AsyncMFS.prototype[asyncProp]

  AsyncMFS.prototype[asyncProp] = function (...args) {
    // Callback support for webpack
    if (origAsync && args.length && typeof args[args.length - 1] === 'function') {
      return origAsync.call(this, ...args)
    }

    try {
      return Promise.resolve(MFS.prototype[prop].call(this, ...args))
    } catch (error) {
      return Promise.reject(error)
    }
  }
}