Use npm XCode to add localization metadata to an iOS project generated by GameMaker.

xcode-loc.ts

import { dirname, basename, join } from 'path';
import fs from 'fs-extra';
//@ts-ignore
import xcode from 'xcode';

export async function addLocalizationWithXCode(
  projectPath: string,
  languages: L10nLang[],
) {
  const languageFileRootDir = getLanguageFileRootDir(projectPath);
  // No types available. See https://www.npmjs.com/package/xcode for API
  const parsedProj = xcode.project(projectPath);
  const gameLanguages = languages;
  const englishFileName = join(
    languageFileRootDir,
    'en.lproj',
    'InfoPlist.strings',
  );

  return new Promise((resolve, reject) => {
    parsedProj.parse(function (err: any) {
      if (err) {
        return reject(err);
      } else {
        gameLanguages.forEach((language) => {
          if (language != 'en-US') {
            //GMS's xcodeproj has en-us by default
            //For example, adding "zh-Hans" requires the presence of the file ".../demo/zh-Hans.lproj/InfoPlist.strings"
            const xcodeLang = l10nToXcode(language);
            const languageFileDir = `${xcodeLang.replace(
              /"/g,
              '',
            )}.lproj/InfoPlist.strings`;
            const languageFileDirAbsolute = join(
              languageFileRootDir,
              languageFileDir,
            );
            fs.ensureFileSync(languageFileDirAbsolute);
            fs.copyFileSync(englishFileName, languageFileDirAbsolute);

            const groupKey = parsedProj.findPBXVariantGroupKey({
              name: 'InfoPlist.strings',
            });
            /**
             *
             * @param path {String}
             * @param group {String} group key
             * @param opt {Object} see pbxFile for avail options
             * @returns {Object} file; see pbxFile
             */
            parsedProj.addFile(languageFileDir, groupKey);
            parsedProj.addKnownRegion(xcodeLang);
          }
        });
        fs.writeFileSync(projectPath, parsedProj.writeSync());
        return resolve(
          `Successfully added localization for ${languages.join(',')}`,
        );
      }
    });
  });
}

const l10nToXcodeDic = {
  'zh-CN': '"zh-Hans"',
  'ru-RU': 'ru',
  'es-XL': 'es',
  'es-ES': '"es-419"',
  'pt-BR': '"pt-BR"',
  'de-DE': 'de',
  'it-IT': 'it',
  'fr-FR': 'fr',
  'ja-JP': 'ja',
  'ko-KR': 'ko',
  'zh-TW': '"zh-Hant"',
  'en-US': 'en',
};

export type L10nLang = keyof typeof l10nToXcodeDic;

function l10nToXcode(l10nLang: L10nLang) {
  const xcodeLang = l10nToXcodeDic[l10nLang];
  if (xcodeLang) {
    return xcodeLang;
  } else {
    throw new Error(`${l10nLang} does not exist in the l10nToXcodeDic!`);
  }
}

/**
 * @desc ".../demo.xcodeproj/project.pbxproj" should return ".../demo/"
 * @param projectPath
 */
function getLanguageFileRootDir(projectPath: string) {
  const projectDir = dirname(projectPath);
  const projectName = basename(projectDir, '.xcodeproj');
  const languageFileRootDir = join(dirname(projectDir), projectName);
  return languageFileRootDir;
}