cypress/packages/server/lib/files.js

const Bluebird = require('bluebird')
const path = require('path')
const { fs } = require('./util/fs')

module.exports = {
  readFile (projectRoot, options = {}) {
    const filePath = path.resolve(projectRoot, options.file)
    const readFn = (path.extname(filePath) === '.json' && options.encoding !== null) ? fs.readJsonAsync : fs.readFileAsync

    // https://github.com/cypress-io/cypress/issues/1558
    // If no encoding is specified, then Cypress has historically defaulted
    // to `utf8`, because of it's focus on text files. This is in contrast to
    // NodeJs, which defaults to binary. We allow users to pass in `null`
    // to restore the default node behavior.
    return readFn(filePath, options.encoding === undefined ? 'utf8' : options.encoding)
    .then((contents) => {
      return {
        contents,
        filePath,
      }
    })
    .catch((err) => {
      err.originalFilePath = options.file
      err.filePath = filePath
      throw err
    })
  },

  readFiles (projectRoot, options = {}) {
    return Bluebird.map(options.files, (file) => {
      return this.readFile(projectRoot, {
        file: file.path,
        encoding: file.encoding,
      })
      .then(({ contents, filePath }) => {
        return {
          ...file,
          filePath,
          contents,
        }
      })
    })
  },

  writeFile (projectRoot, options = {}) {
    const filePath = path.resolve(projectRoot, options.fileName)
    const writeOptions = {
      encoding: options.encoding === undefined ? 'utf8' : options.encoding,
      flag: options.flag || 'w',
    }

    return fs.outputFile(filePath, options.contents, writeOptions)
    .then(() => {
      return {
        contents: options.contents,
        filePath,
      }
    })
    .catch((err) => {
      err.filePath = filePath
      throw err
    })
  },
}