source: node_modules/fs-extra/lib/fs/index.js

'use strict'
// This is adapted from https://github.com/normalize/mz
// Copyright (c) 2014-2016 Jonathan Ong me@jongleberry.com and Contributors
const u = require('universalify').fromCallback
const fs = require('graceful-fs')

const api = [
  'access',
  'appendFile',
  'chmod',
  'chown',
  'close',
  'copyFile',
  'fchmod',
  'fchown',
  'fdatasync',
  'fstat',
  'fsync',
  'ftruncate',
  'futimes',
  'lchmod',
  'lchown',
  'link',
  'lstat',
  'mkdir',
  'mkdtemp',
  'open',
  'opendir',
  'readdir',
  'readFile',
  'readlink',
  'realpath',
  'rename',
  'rm',
  'rmdir',
  'stat',
  'symlink',
  'truncate',
  'unlink',
  'utimes',
  'writeFile'
].filter(key => {
  // Some commands are not available on some systems. Ex:
  // fs.opendir was added in Node.js v12.12.0
  // fs.rm was added in Node.js v14.14.0
  // fs.lchown is not available on at least some Linux
  return typeof fs[key] === 'function'
})

// Export all keys:
Object.keys(fs).forEach(key => {
  if (key === 'promises') {
    // fs.promises is a getter property that triggers ExperimentalWarning
    // Don't re-export it here, the getter is defined in "lib/index.js"
    return
  }
  exports[key] = fs[key]
})

// Universalify async methods:
api.forEach(method => {
  exports[method] = u(fs[method])
})

// We differ from mz/fs in that we still ship the old, broken, fs.exists()
// since we are a drop-in replacement for the native module
exports.exists = function (filename, callback) {
  if (typeof callback === 'function') {
    return fs.exists(filename, callback)
  }
  return new Promise(resolve => {
    return fs.exists(filename, resolve)
  })
}

// fs.read(), fs.write(), & fs.writev() need special treatment due to multiple callback args

exports.read = function (fd, buffer, offset, length, position, callback) {
  if (typeof callback === 'function') {
    return fs.read(fd, buffer, offset, length, position, callback)
  }
  return new Promise((resolve, reject) => {
    fs.read(fd, buffer, offset, length, position, (err, bytesRead, buffer) => {
      if (err) return reject(err)
      resolve({ bytesRead, buffer })
    })
  })
}

// Function signature can be
// fs.write(fd, buffer[, offset[, length[, position]]], callback)
// OR
// fs.write(fd, string[, position[, encoding]], callback)
// We need to handle both cases, so we use ...args
exports.write = function (fd, buffer, ...args) {
  if (typeof args[args.length - 1] === 'function') {
    return fs.write(fd, buffer, ...args)
  }

  return new Promise((resolve, reject) => {
    fs.write(fd, buffer, ...args, (err, bytesWritten, buffer) => {
      if (err) return reject(err)
      resolve({ bytesWritten, buffer })
    })
  })
}

// fs.writev only available in Node v12.9.0+
if (typeof fs.writev === 'function') {
  // Function signature is
  // s.writev(fd, buffers[, position], callback)
  // We need to handle the optional arg, so we use ...args
  exports.writev = function (fd, buffers, ...args) {
    if (typeof args[args.length - 1] === 'function') {
      return fs.writev(fd, buffers, ...args)
    }

    return new Promise((resolve, reject) => {
      fs.writev(fd, buffers, ...args, (err, bytesWritten, buffers) => {
        if (err) return reject(err)
        resolve({ bytesWritten, buffers })
      })
    })
  }
}

// fs.realpath.native only available in Node v9.2+
if (typeof fs.realpath.native === 'function') {
  exports.realpath.native = u(fs.realpath.native)
}