fix: Skip lipo if native module is already universal. Add native module fixtures for lipo tests

jest.setup.ts

@@ -1,10 +1,34 @@
+import { execFileSync } from 'child_process';
 import * as fs from 'fs-extra';
 import * as path from 'path';
-import { appsDir, asarsDir, templateApp } from './test/util';
+import { appsDir, asarsDir, fixtureDir, templateApp } from './test/util';
+
+// generates binaries from hello-world.c
+// hello-world-universal, hello-world-x86_64, hello-world-arm64
+const generateMachO = () => {
+  const src = path.resolve(fixtureDir, 'hello-world.c');
+
+  const outputFiles = ['x86_64', 'arm64'].map((arch) => {
+    const machO = path.resolve(appsDir, `hello-world-${arch === 'x86_64' ? 'x64' : arch}`);
+    execFileSync('clang', ['-arch', arch, '-o', machO, src]);
+    return machO;
+  });
+
+  execFileSync('lipo', [
+    ...outputFiles,
+    '-create',
+    '-output',
+    path.resolve(appsDir, 'hello-world-universal'),
+  ]);
+};
 
 export default async () => {
   await fs.remove(appsDir);
   await fs.mkdirp(appsDir);
+
+  // generate mach-o binaries to be leveraged in lipo tests
+  generateMachO();
+
   await templateApp('Arm64Asar.app', 'arm64', async (appPath) => {
     await fs.copy(
       path.resolve(asarsDir, 'app.asar'),

src/asar-utils.ts

@@ -148,14 +148,13 @@ export const mergeASARs = async ({
     const x64Content = asar.extractFile(x64AsarPath, file);
     const arm64Content = asar.extractFile(arm64AsarPath, file);
 
+    // Skip file if the same content
     if (x64Content.compare(arm64Content) === 0) {
       continue;
     }
 
-    if (
-      MACHO_UNIVERSAL_MAGIC.has(x64Content.readUInt32LE(0)) &&
-      MACHO_UNIVERSAL_MAGIC.has(arm64Content.readUInt32LE(0))
-    ) {
+    // Skip universal Mach-O files.
+    if (isUniversalMachO(x64Content)) {
       continue;
     }
 
@@ -223,3 +222,7 @@ export const mergeASARs = async ({
     await Promise.all([fs.remove(x64Dir), fs.remove(arm64Dir)]);
   }
 };
+
+export const isUniversalMachO = (fileContent: Buffer) => {
+  return MACHO_UNIVERSAL_MAGIC.has(fileContent.readUInt32LE(0));
+};

src/file-utils.ts

@@ -1,6 +1,7 @@
 import { spawn, ExitCodeError } from '@malept/cross-spawn-promise';
 import * as fs from 'fs-extra';
 import * as path from 'path';
+import { promises as stream } from 'node:stream';
 
 const MACHO_PREFIX = 'Mach-O ';
 
@@ -71,3 +72,14 @@ export const getAllAppFiles = async (appPath: string): Promise<AppFile[]> => {
 
   return files;
 };
+
+export const readMachOHeader = async (path: string) => {
+  const chunks: Buffer[] = [];
+  // no need to read the entire file, we only need the first 4 bytes of the file to determine the header
+  await stream.pipeline(fs.createReadStream(path, { start: 0, end: 3 }), async function* (source) {
+    for await (const chunk of source) {
+      chunks.push(chunk);
+    }
+  });
+  return Buffer.concat(chunks);
+};

src/index.ts

@@ -1,14 +1,14 @@
-import { spawn } from '@malept/cross-spawn-promise';
 import * as asar from '@electron/asar';
+import { spawn } from '@malept/cross-spawn-promise';
+import * as dircompare from 'dir-compare';
 import * as fs from 'fs-extra';
 import { minimatch } from 'minimatch';
 import * as os from 'os';
 import * as path from 'path';
 import * as plist from 'plist';
-import * as dircompare from 'dir-compare';
 
-import { AppFile, AppFileType, getAllAppFiles } from './file-utils';
-import { AsarMode, detectAsarMode, mergeASARs } from './asar-utils';
+import { AsarMode, detectAsarMode, isUniversalMachO, mergeASARs } from './asar-utils';
+import { AppFile, AppFileType, getAllAppFiles, readMachOHeader } from './file-utils';
 import { sha } from './sha';
 import { d } from './debug';
 import { computeIntegrityData } from './integrity';
@@ -162,6 +162,15 @@ export const makeUniversalApp = async (opts: MakeUniversalOpts): Promise<void> =
       const first = await fs.realpath(path.resolve(tmpApp, machOFile.relativePath));
       const second = await fs.realpath(path.resolve(opts.arm64AppPath, machOFile.relativePath));
 
+      if (
+        isUniversalMachO(await readMachOHeader(first)) &&
+        isUniversalMachO(await readMachOHeader(second))
+      ) {
+        d(machOFile.relativePath, `is already universal across builds, skipping lipo`);
+        knownMergedMachOFiles.add(machOFile.relativePath);
+        continue;
+      }
+
       const x64Sha = await sha(path.resolve(opts.x64AppPath, machOFile.relativePath));
       const arm64Sha = await sha(path.resolve(opts.arm64AppPath, machOFile.relativePath));
       if (x64Sha === arm64Sha) {