next.js/packages/next/build/is-writeable.ts

import fs from 'fs'
import {promisify} from 'util'

const access = promisify(fs.access)

export async function isWriteable (directory: string): Promise<boolean> {
  try {
    await access(directory, (fs.constants || fs).W_OK)
    return true
  } catch (err) {
    return false
  }
}