build.js

/* eslint-disable no-magic-numbers, unicorn/no-process-exit, no-console, prefer-template */
// 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("react-dev-utils/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 { checkBrowsers } = require("react-dev-utils/browsersHelper")

const configFactory = require("../config/webpack.config")
const paths = require("../config/paths")

const {
  measureFileSizesBeforeBuild,
  printFileSizesAfterBuild,
} = FileSizeReporter
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

// Generate configuration
const config = configFactory("production")

// We require that you explicitly set browsers and do not fall back to
// browserslist defaults.
checkBrowsers(paths.appPath, isInteractive)
  .then(() => {
    // First, read the current file sizes in build directory.
    // This lets us display how much they changed later.
    return 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 !== 0) {
        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()

      // eslint-disable-next-line global-require, import/no-dynamic-require
      const appPackage = require(paths.appPackageJson)
      const { publicUrl } = paths
      const { publicPath } = config.output
      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((error) => {
    if (error && error.message) {
      console.log(error.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 !== 0) {
        // 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 !== 0
      // ) {
      //   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,
  })
}