metu.life/config/webpack/generateLocalePacks.js

// A message from upstream:
// ========================
// To avoid adding a lot of boilerplate, locale packs are
// automatically generated here. These are written into the tmp/
// directory and then used to generate locale_en.js, locale_fr.js, etc.

// Glitch note:
// ============
// This code has been entirely rewritten to support glitch flavours.
// However, the underlying process is exactly the same.

const { existsSync, readdirSync, writeFileSync } = require('fs');
const { join, resolve } = require('path');
const rimraf = require('rimraf');
const mkdirp = require('mkdirp');
const { flavours } = require('./configuration.js');

module.exports = Object.keys(flavours).reduce(function (map, entry) {
  const flavour = flavours[entry];
  if (!flavour.locales) {
    return map;
  }
  const locales = readdirSync(flavour.locales).filter(
    filename => /\.js(?:on)?$/.test(filename) && !/defaultMessages|whitelist|index/.test(filename)
  );
  const outPath = resolve('tmp', 'locales', entry);

  rimraf.sync(outPath);
  mkdirp.sync(outPath);

  locales.forEach(function (locale) {
    const localeName = locale.replace(/\.js(?:on)?$/, '');
    const localePath = join(outPath, `${localeName}.js`);
    const baseLocale = localeName.split('-')[0]; // e.g. 'zh-TW' -> 'zh'
    const localeDataPath = [
      // first try react-intl
      `node_modules/react-intl/locale-data/${baseLocale}.js`,
      // then check locales/locale-data
      `app/javascript/locales/locale-data/${baseLocale}.js`,
      // fall back to English (this is what react-intl does anyway)
      'node_modules/react-intl/locale-data/en.js',
    ].filter(
      filename => existsSync(filename)
    ).map(
      filename => filename.replace(/(?:node_modules|app\/javascript)\//, '')
    )[0];
    const localeContent = `//
// locales/${entry}/${localeName}.js
// automatically generated by generateLocalePacks.js
//

import messages from '../../../${flavour.locales}/${locale.replace(/\.js$/, '')}';
import localeData from '${localeDataPath}';
import { setLocale } from 'locales';

setLocale({
  localeData,
  messages,
});
`;
    writeFileSync(localePath, localeContent, 'utf8');
    map[`locales/${entry}/${localeName}`] = localePath;
  });

  return map;
}, {});