text: // Do this as the first thing so that any code reading it knows the right env.
  process.env.BABEL_ENV = 'production';
  process.env.NODE_ENV = 'production';
  
  // Makes the script crash on unhandled rejections instead of silently
  // ignoring them. In the future, promise rejections that are not handled will
  // terminate the Node.js process with a non-zero exit code.
  process.on('unhandledRejection', err => {
    throw err;
  });
  
  // Ensure environment variables are read.
  require('../config/env');
  
  
  const path = require('path');
  const chalk = require('chalk');
  const fs = require('fs-extra');
  const webpack = require('webpack');
  const bfj = require('bfj');
  const checkRequiredFiles = require('react-dev-utils/checkRequiredFiles');
  const formatWebpackMessages = require('react-dev-utils/formatWebpackMessages');
  const printHostingInstructions = require('react-dev-utils/printHostingInstructions');
  const FileSizeReporter = require('react-dev-utils/FileSizeReporter');
  const printBuildError = require('react-dev-utils/printBuildError');
  
  const measureFileSizesBeforeBuild = FileSizeReporter.measureFileSizesBeforeBuild;
  const printFileSizesAfterBuild = FileSizeReporter.printFileSizesAfterBuild;
  const useYarn = fs.existsSync(paths.yarnLockFile);
  
  // These sizes are pretty large. We'll warn for bundles exceeding them.
  const WARN_AFTER_BUNDLE_GZIP_SIZE = 512 * 1024;
  const WARN_AFTER_CHUNK_GZIP_SIZE = 1024 * 1024;
  
  const isInteractive = process.stdout.isTTY;
  
  // Warn and crash if required files are missing
  if (!checkRequiredFiles([paths.appHtml, paths.appIndexJs])) {
    process.exit(1);
  }
  
  // Process CLI arguments
  const argv = process.argv.slice(2);
  const writeStatsJson = argv.indexOf('--stats') !== -1;
  
  // We require that you explictly set browsers and do not fall back to
  // browserslist defaults.
  const { checkBrowsers } = require('react-dev-utils/browsersHelper');
  const paths = require('../config/paths');
  const config = require('../config/webpack.config.prod');
  
  checkBrowsers(paths.appPath, isInteractive)
    .then(() => measureFileSizesBeforeBuild(paths.appBuild),
    )
    .then(previousFileSizes => {
      // Remove all content but keep the directory so that
      // if you're in it, you don't end up in Trash
      fs.emptyDirSync(paths.appBuild);
      // Merge with the public folder
      copyPublicFolder();
      // Start the webpack build
      return build(previousFileSizes);
    })
    .then(
      ({ stats, previousFileSizes, warnings }) => {
        if (warnings.length) {
          console.log(chalk.yellow('Compiled with warnings.\n'));
          console.log(warnings.join('\n\n'));
          console.log(
            `\nSearch for the ${
              chalk.underline(chalk.yellow('keywords'))
            } to learn more about each warning.`,
          );
          console.log(
            `To ignore, add ${
              chalk.cyan('// eslint-disable-next-line')
            } to the line before.\n`,
          );
        } else {
          console.log(chalk.green('Compiled successfully.\n'));
        }
  
        console.log('File sizes after gzip:\n');
        printFileSizesAfterBuild(
          stats,
          previousFileSizes,
          paths.appBuild,
          WARN_AFTER_BUNDLE_GZIP_SIZE,
          WARN_AFTER_CHUNK_GZIP_SIZE,
        );
        console.log();
  
        const appPackage = require(paths.appPackageJson);
        const publicUrl = paths.publicUrl;
        const publicPath = config.output.publicPath;
        const buildFolder = path.relative(process.cwd(), paths.appBuild);
        printHostingInstructions(
          appPackage,
          publicUrl,
          publicPath,
          buildFolder,
          useYarn,
        );
      },
      err => {
        console.log(chalk.red('Failed to compile.\n'));
        printBuildError(err);
        process.exit(1);
      },
    )
    .catch(err => {
      if (err && err.message) {
        console.log(err.message);
      }
      process.exit(1);
    });
  
  // Create the production build and print the deployment instructions.
  function build(previousFileSizes) {
    console.log('Creating an optimized production build...');
  
    const compiler = webpack(config);
    return new Promise((resolve, reject) => {
      compiler.run((err, stats) => {
        let messages;
        if (err) {
          if (!err.message) {
            return reject(err);
          }
          messages = formatWebpackMessages({
            errors: [err.message],
            warnings: [],
          });
        } else {
          messages = formatWebpackMessages(
            stats.toJson({ all: false, warnings: true, errors: true }),
          );
        }
        if (messages.errors.length) {
          // Only keep the first error. Others are often indicative
          // of the same problem, but confuse the reader with noise.
          if (messages.errors.length > 1) {
            messages.errors.length = 1;
          }
          return reject(new Error(messages.errors.join('\n\n')));
        }
        if (
          process.env.CI
          && (typeof process.env.CI !== 'string'
            || process.env.CI.toLowerCase() !== 'false')
          && messages.warnings.length
        ) {
          console.log(
            chalk.yellow(
              '\nTreating warnings as errors because process.env.CI = true.\n'
                + 'Most CI servers set it automatically.\n',
            ),
          );
          return reject(new Error(messages.warnings.join('\n\n')));
        }
  
        const resolveArgs = {
          stats,
          previousFileSizes,
          warnings: messages.warnings,
        };
        if (writeStatsJson) {
          return bfj
            .write(`${paths.appBuild}/bundle-stats.json`, stats.toJson())
            .then(() => resolve(resolveArgs))
            .catch(error => reject(new Error(error)));
        }
  
        return resolve(resolveArgs);
      });
    });
  }
  
  function copyPublicFolder() {
    fs.copySync(paths.appPublic, paths.appBuild, {
      dereference: true,
      filter: file => file !== paths.appHtml,
    });
  }
  