create-new-app/modules/keepOldFileContent.js

Easily generate a new React application, optionally with Express & MongoDB.

/*
  This module will create CONTENTS for a given source path, including existing
  content the target file exists already.

  It looks to see if the file exists, comments out all that content, prepends
  a message at the top of the file saying it did so, then writes the new
  content below the prepended message.

  All this kicks in if the user used the `--force` option.
  We don't want to overwrite user data.
*/

const fs = require('fs-extra')
const createBorderedCenteredComment = require('./createBorderedCenteredComment')

function keepOldFileContent({sourcePath, destinationPath, newContent}) {
  const isJsFile = destinationPath.endsWith('.js')
  const commentChar = isJsFile ? '//' : '#'
  const comments = [
    'The contents of this file have been modified by',
    'create-new-app (https://github.com/qodesmith/create-new-app).',
    'The original contents have been commented out below.',
  ]
  const cautionMessage = createBorderedCenteredComment(comments, commentChar)

  // Check for the original file & comment out existing content.
  let originalContent = null
  try {
    originalContent = fs
      .readFileSync(destinationPath, 'utf8')
      .split('\n')
      .map((lineContent, i, arr) => {
        if (i === arr.length - 1 && !lineContent.trim()) return '' // Avoid commenting out a blank last line.
        return `${commentChar} ${lineContent}`
      })
      .join('\n')
  } catch (e) {}

  const finalContent = newContent || fs.readFileSync(sourcePath, 'utf8')

  if (originalContent) {
    return [
      cautionMessage,
      '\n',
      finalContent,
      '\n\n',
      createBorderedCenteredComment(['ORIGINAL CONTENTS BELOW'], commentChar),
      '\n',
      originalContent,
    ].join('\n')
  }

  return finalContent
}

module.exports = keepOldFileContent