nodejs unreal plugin build script (macOS)

build.mjs

import { readFile, readdir } from 'fs/promises'
import { existsSync } from 'fs';
import { resolve, join, sep } from 'path'
import { argv } from 'process';
import { spawn } from 'child_process';

const exec = (
  cmd,
  args,
) => new Promise((resolve, reject) => {
  const cp = spawn(cmd, args, { stdio: ['ignore', 'inherit', 'inherit'] });
  cp.on('exit', (code) => (code && code !== 0) ? reject(code) : resolve(0));
});

const getEngineVersion = async (uprojectPath) => {
  const uproject = await readFile(uprojectPath, 'utf-8');
  const project = JSON.parse(uproject);
  const engineVersion = project.EngineAssociation;
  if (!engineVersion) throw new Error(`Could not find engine version in ${uprojectPath}`);
  return engineVersion;
}

const getInstallLocation = async (engineVersion) => {
  const installIniPath = join(process.env.HOME, 'Library/Application Support/Epic/UnrealEngine/Install.ini');
  const installIni = await readFile(installIniPath, 'utf-8');
  const matches = installIni.match(new RegExp(`^{${engineVersion}}=(.*)`, 'gm'));
  let installLocation = matches ? matches[1] : "";
  
  if (!installLocation) {
    const dirListing = await readdir(join(process.env.HOME, 'Library/Application Support/Epic/UnrealEngine'));
    const configCacheFiles = dirListing.filter(file => file.startsWith('XmlConfigCache'));
    const configCache = configCacheFiles.find(file => file.includes(`UE_${engineVersion}`));
    if (!configCache) throw new Error(`Could not find Unreal Engine ${engineVersion} installation location`);

    const encodedPath = configCache.match(/XmlConfigCache-(.*)\.bin/)[1] ?? "";
    if (encodedPath) installLocation = encodedPath.replace(/\+/g, sep);
  }

  if (!installLocation) throw new Error(`Could not find Unreal Engine ${engineVersion} installation location`);
  return installLocation;
}

const getRunUATPath = async (engineVersion) => {
  const installLocation = await getInstallLocation(engineVersion);
  const runUATPath = join(installLocation, `Engine/Build/BatchFiles/RunUAT.${process.platform === 'win32' ? 'bat' : 'sh'}`);
  if (!existsSync(runUATPath)) throw new Error(`Could not find RunUAT script in ${installLocation}`);
  return runUATPath;
}

const getPluginPath = async (uprojectPath, pluginName) => {
  const uprojectDir = resolve(uprojectPath, '..');
  const pluginDir = join(uprojectDir, 'Plugins', pluginName);
  const pluginFile = join(pluginDir, `${pluginName}.uplugin`);
  if (!existsSync(pluginFile)) throw new Error(`Could not find plugin ${pluginName} in ${pluginDir}`);
  return pluginFile;
}

const buildPlugin = async (engineVersion, pluginPath) => {
  const runUATPath = await getRunUATPath(engineVersion);  
  const exitCode = await exec(runUATPath, ["BuildPlugin", `-Plugin=${pluginPath}`, `-Package=${process.cwd()}/Packages/Mac`, "-Rocket", "-TargetPlatforms=Mac"]);
  if (exitCode !== 0) throw new Error(`Failed to build plugin ${pluginPath}`);
}

const main = async () => {
  if (argv.length < 4) throw new Error('Usage: build.mjs <uproject path> <plugin name>');
  if (process.platform !== 'darwin') throw new Error('TODO: Need to modify this script to work on windows and linux');

  const uprojectPath = resolve(argv[2]);
  const plugin = await getPluginPath(uprojectPath, argv[3]);
  const engineVersion = await getEngineVersion(uprojectPath);
  await buildPlugin(engineVersion, plugin);
}

await main();