serverless/lib/utils/fs/write-file.js

import { promises as fsp } from 'fs'
import fse from 'fs-extra'
import path from 'path'
import jc from 'json-cycle'
import yaml from 'js-yaml'

async function writeFile(filePath, conts, cycles) {
  let contents = conts || ''

  return fse.mkdirs(path.dirname(filePath)).then(() => {
    if (filePath.indexOf('.json') !== -1 && typeof contents !== 'string') {
      if (cycles) {
        contents = jc.stringify(contents, null, 2)
      } else {
        contents = JSON.stringify(contents, null, 2)
      }
    }

    const yamlFileExists = filePath.indexOf('.yaml') !== -1
    const ymlFileExists = filePath.indexOf('.yml') !== -1

    if ((yamlFileExists || ymlFileExists) && typeof contents !== 'string') {
      contents = yaml.dump(contents)
    }

    return fsp.writeFile(filePath, contents)
  })
}

export default writeFile