index.ts

import { spawn } from '@malept/cross-spawn-promise';
import * as asar from 'asar';
import * as crypto from 'crypto';
import * as fs from 'fs-extra';
import * as os from 'os';
import * as path from 'path';

const MACHO_PREFIX = 'Mach-O ';
const macho = require('macho');

const machoParse = async (
  p: string,
): Promise<{
  bits: number;
  cpu: {
    type: 'x86_64' | 'arm64';
    subtype: string;
  };
}> => {
  return macho.parse(await fs.readFile(p));
};

type MakeUniversalOpts = {
  /**
   * Absolute file system path to the x64 version of your application.  E.g. /Foo/bar/MyApp_x64.app
   */
  x64AppPath: string;
  /**
   * Absolute file system path to the arm64 version of your application.  E.g. /Foo/bar/MyApp_arm64.app
   */
  arm64AppPath: string;
  /**
   * Absolute file system path you want the universal app to be written to.  E.g. /Foo/var/MyApp_universal.app
   *
   * If this file exists it will be overwritten ONLY if "force" is set to true
   */
  outAppPath: string;
  /**
   * Forcefully overwrite any existing files that are in the way of generating the universal application
   */
  force: boolean;
};

enum AsarMode {
  NO_ASAR,
  HAS_ASAR,
}

const detectAsarMode = async (appPath: string) => {
  const asarPath = path.resolve(appPath, 'Contents', 'Resources', 'app.asar');
  const asarUnpackedPath = path.resolve(appPath, 'Contents', 'Resources', 'app.asar.unpacked');

  if (!(await fs.pathExists(asarPath))) return AsarMode.NO_ASAR;
  
  return AsarMode.HAS_ASAR;
};

enum AppFileType {
  MACHO,
  PLAIN,
  SNAPSHOT,
  APP_CODE,
}

type AppFile = {
  relativePath: string;
  type: AppFileType;
}

const getAllFiles = async (appPath: string): Promise<AppFile[]> => {
  const files: AppFile[] = [];

  const visited = new Set<string>();
  const traverse = async (p: string) => {
    p = await fs.realpath(p);
    if (visited.has(p)) return;
    visited.add(p);

    const info = await fs.stat(p);
    if (info.isSymbolicLink()) return;
    if (info.isFile()) {
      let fileType = AppFileType.PLAIN;

      const fileOutput = await spawn('file', ['--brief', '--no-pad', p]);
      if (p.includes('app.asar')) {
        fileType = AppFileType.APP_CODE;
      } else if (fileOutput.startsWith(MACHO_PREFIX)) {
        fileType = AppFileType.MACHO;
      } else if (p.endsWith('.bin')) {
        fileType = AppFileType.SNAPSHOT;
      }

      files.push({
        relativePath: path.relative(appPath, p),
        type: fileType,
      });
    }

    if (info.isDirectory()) {
      for (const child of await fs.readdir(p)) {
        await traverse(path.resolve(p, child));
      }
    }
  };
  await traverse(appPath);

  return files;
};

const dupedFiles = (files: AppFile[]) => files.filter(f => f.type !== AppFileType.SNAPSHOT && f.type !== AppFileType.APP_CODE);

const sha = async (filePath: string) => {
  return crypto.createHash('sha256').update(fs.readFileSync(filePath)).digest('hex');
}

export const makeUniversalApp = async (opts: MakeUniversalOpts): Promise<void> => {
  if (process.platform !== 'darwin')
    throw new Error('@electron/universal is only supported on darwin platforms');
  if (!opts.x64AppPath || !path.isAbsolute(opts.x64AppPath))
    throw new Error('Expected opts.x64AppPath to be an absolute path but it was not');
  if (!opts.arm64AppPath || !path.isAbsolute(opts.arm64AppPath))
    throw new Error('Expected opts.arm64AppPath to be an absolute path but it was not');
  if (!opts.outAppPath || !path.isAbsolute(opts.outAppPath))
    throw new Error('Expected opts.outAppPath to be an absolute path but it was not');

  if (await fs.pathExists(opts.outAppPath)) {
    if (!opts.force) {
      throw new Error(
        `The out path "${opts.outAppPath}" already exists and force is not set to true`,
      );
    } else {
      await fs.remove(opts.outAppPath);
    }
  }

  const x64AsarMode = await detectAsarMode(opts.x64AppPath);
  const arm64AsarMode = await detectAsarMode(opts.arm64AppPath);

  if (x64AsarMode !== arm64AsarMode)
    throw new Error(
      'Both the x64 and arm64 versions of your application need to have been built with the same asar settings (enabled vs disabled)',
    );

  const tmpDir = await fs.mkdtemp(path.resolve(os.tmpdir(), 'electron-universal-'));

  try {
    const tmpApp = path.resolve(tmpDir, 'Tmp.app');
    await spawn('cp', ['-R', opts.x64AppPath, tmpApp]);

    const uniqueToX64: string[] = [];
    const uniqueToArm64: string[] = [];
    const x64Files = await getAllFiles(await fs.realpath(tmpApp));
    const arm64Files = await getAllFiles(opts.arm64AppPath);

    for (const file of dupedFiles(x64Files)) {
      if (!arm64Files.some(f => f.relativePath === file.relativePath)) uniqueToX64.push(file.relativePath);
    }
    for (const file of dupedFiles(arm64Files)) {
      if (!x64Files.some(f => f.relativePath === file.relativePath)) uniqueToArm64.push(file.relativePath);
    }
    if (uniqueToX64.length !== 0 || uniqueToArm64.length !== 0) {
      console.error({
        uniqueToX64,
        uniqueToArm64,
      });
      throw new Error(
        'While trying to merge mach-o files across your apps we found a mismatch, the number of mach-o files is not the same between the arm64 and x64 builds',
      );
    }

    for (const file of x64Files.filter(f => f.type === AppFileType.PLAIN)) {
      const x64Sha = await sha(path.resolve(opts.x64AppPath, file.relativePath));
      const arm64Sha = await sha(path.resolve(opts.arm64AppPath, file.relativePath));
      if (x64Sha !== arm64Sha) {
        console.error(`${x64Sha} !== ${arm64Sha}`);
        throw new Error(`Expected all non-binary files to have identical SHAs when creating a universal build but "${file.relativePath}" did not`);
      }
    }

    for (const machOFile of x64Files.filter(f => f.type === AppFileType.MACHO)) {
      await spawn('lipo', [
        await fs.realpath(path.resolve(tmpApp, machOFile.relativePath)),
        await fs.realpath(path.resolve(opts.arm64AppPath, machOFile.relativePath)),
        '-create',
        '-output',
        await fs.realpath(path.resolve(tmpApp, machOFile.relativePath)),
      ]);
    }

    if (x64AsarMode === AsarMode.NO_ASAR) {
      await fs.move(path.resolve(tmpApp, 'Contents', 'Resources', 'app'), path.resolve(tmpApp, 'Contents', 'Resources', 'x64.app'));
      await fs.copy(path.resolve(opts.arm64AppPath, 'Contents', 'Resources', 'app'), path.resolve(tmpApp, 'Contents', 'Resources', 'arm64.app'));
    } else {
      await fs.move(path.resolve(tmpApp, 'Contents', 'Resources', 'app.asar'), path.resolve(tmpApp, 'Contents', 'Resources', 'x64.app.asar'));
      const x64Unpacked = path.resolve(tmpApp, 'Contents', 'Resources', 'app.asar.unpacked');
      if (await fs.pathExists(x64Unpacked)) {
        await fs.move(x64Unpacked, path.resolve(tmpApp, 'Contents', 'Resources', 'x64.app.asar.unpacked'));
      }

      await fs.copy(path.resolve(opts.arm64AppPath, 'Contents', 'Resources', 'app.asar'), path.resolve(tmpApp, 'Contents', 'Resources', 'arm64.app.asar'));
      const arm64Unpacked = path.resolve(opts.arm64AppPath, 'Contents', 'Resources', 'app.asar.unpacked');
      if (await fs.pathExists(arm64Unpacked)) {
        await fs.copy(arm64Unpacked, path.resolve(tmpApp, 'Contents', 'Resources', 'arm64.app.asar.unpacked'));
      }
    }

    const entryAsar = path.resolve(tmpDir, 'entry-asar');
    await fs.mkdir(entryAsar);
    await fs.copy(path.resolve(__dirname, '..', '..', 'entry-asar', 'index.js'), path.resolve(entryAsar, 'index.js'));
    let pj: any;
    if (x64AsarMode === AsarMode.NO_ASAR) {
      pj = await fs.readJson(path.resolve(opts.x64AppPath, 'Contents', 'Resources', 'app', 'package.json'));
    } else {
      pj = JSON.parse((await asar.extractFile(path.resolve(opts.x64AppPath, 'Contents', 'Resources', 'app.asar'), 'package.json')).toString('utf8'));
    }
    pj.main = 'index.js';
    await fs.writeJson(path.resolve(entryAsar, 'package.json'), pj);
    await asar.createPackage(entryAsar, path.resolve(tmpApp, 'Contents', 'Resources', 'app.asar'));

    for (const snapshotsFile of arm64Files.filter(f => f.type === AppFileType.SNAPSHOT)) {
      await fs.copy(path.resolve(opts.arm64AppPath, snapshotsFile.relativePath), path.resolve(tmpApp, snapshotsFile.relativePath));
    }

    await spawn('mv', [tmpApp, opts.outAppPath]);
  } catch (err) {
    throw err;
  } finally {
    await fs.remove(tmpDir);
  }
};