fix: hermes-compiler path for RN 0.82+ in the hermes bytecode plugin (#1332)

Author: ismarbesic

.changeset/cuddly-months-think.md

@@ -0,0 +1,5 @@
+---
+"@callstack/repack": patch
+---
+
+Fix hermes-compiler path for RN 0.82+ in the hermes bytecode plugin

packages/repack/src/plugins/HermesBytecodePlugin/utils/getHermesCLIPath.ts

@@ -1,3 +1,4 @@
+import fs from 'node:fs';
 import os from 'node:os';
 import path from 'node:path';
 
@@ -20,7 +21,7 @@ const getHermesOSBin = (): string | null => {
 /**
  * Determines the path to the Hermes compiler binary.
  *
- * Defaults to './node_modules/react-native/sdks/hermesc/{os-bin}/hermesc'
+ * Defaults to './node_modules/hermes-compiler/hermesc/{os-bin}/hermesc'
  */
 export const getHermesCLIPath = (reactNativePath: string): string => {
   const osBin = getHermesOSBin();
@@ -32,5 +33,19 @@ export const getHermesCLIPath = (reactNativePath: string): string => {
     );
   }
 
+  const hermesCompilerPath = path.join(
+    reactNativePath,
+    '..',
+    'hermes-compiler',
+    'hermesc',
+    osBin,
+    'hermesc'
+  );
+
+  if (fs.existsSync(hermesCompilerPath)) {
+    return hermesCompilerPath;
+  }
+
+  // Fallback to the previous hermesc path in older react native versions, <0.82.
   return path.join(reactNativePath, 'sdks', 'hermesc', osBin, 'hermesc');
 };

packages/repack/src/plugins/__tests__/HermesBytecodePlugin.test.ts

@@ -1,11 +1,14 @@
 import fs from 'node:fs';
+import os from 'node:os';
 import { type Compiler, ModuleFilenameHelpers } from '@rspack/core';
 import execa from 'execa';
 import { HermesBytecodePlugin } from '../HermesBytecodePlugin/index.js';
+import { getHermesCLIPath } from '../HermesBytecodePlugin/utils/getHermesCLIPath.js';
 
 jest.mock('node:fs', () => ({
   __esModule: true,
   default: {
+    existsSync: jest.fn(),
     promises: {
       access: jest.fn(),
       rename: jest.fn(),
@@ -142,4 +145,30 @@ describe('HermesBytecodePlugin', () => {
       expect(execaMock.mock.calls[0][0]).toEqual('path/to/hermesc');
     });
   });
+
+  describe('getHermesCLIPath', () => {
+    const reactNativePath = 'path/to/react-native';
+
+    it('returns new hermes-compiler path when it exists', () => {
+      jest.spyOn(os, 'platform').mockReturnValue('darwin');
+      jest.mocked(fs.existsSync).mockReturnValue(true);
+
+      const hermesPath = getHermesCLIPath(reactNativePath);
+
+      expect(hermesPath).toBe(
+        'path/to/hermes-compiler/hermesc/osx-bin/hermesc'
+      );
+    });
+
+    it('falls back to legacy hermesc path when hermes-compiler does not exist', () => {
+      jest.spyOn(os, 'platform').mockReturnValue('darwin');
+      jest.mocked(fs.existsSync).mockReturnValue(false);
+
+      const hermesPath = getHermesCLIPath(reactNativePath);
+
+      expect(hermesPath).toBe(
+        'path/to/react-native/sdks/hermesc/osx-bin/hermesc'
+      );
+    });
+  });
 });