@callstack/repack/babel-swc-loader make some lib not working

[npcv1999]

Describe the bug

I used the new config in rspack.config.mjs:

module: {
  rules: [
    {
      test: /.[cm]?[jt]sx?$/,
      type: "javascript/auto",
      use: {
        loader: "@callstack/repack/babel-swc-loader",
        parallel: true,
        options: {},
      },
    },
    ...Repack.getAssetTransformRules(),
  ],
}

However, I got an error where react-native-mmkv couldn’t retrieve data saved in storage, and when use @hot-updater/react-native that crash after receive new updater
When I switched back to the old config:

...Repack.getJsTransformRules(),
...Repack.getAssetTransformRules()

everything worked fine.
I’d like to know why this happens.

System Info

System:
  OS: macOS 15.6.1
  CPU: (12) arm64 Apple M4 Pro
  Memory: 103.22 MB / 24.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 20.18.1
    path: /Users/ving/.nvm/versions/node/v20.18.1/bin/node
  Yarn: Not Found
  npm:
    version: 10.8.2
    path: /Users/ving/.nvm/versions/node/v20.18.1/bin/npm
  Watchman:
    version: 2024.12.02.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.16.2
    path: /Users/ving/.rbenv/shims/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 25.0
      - iOS 26.0
      - macOS 26.0
      - tvOS 26.0
      - visionOS 26.0
      - watchOS 26.0
  Android SDK: Not Found
IDEs:
  Android Studio: 2025.1 AI-251.26094.121.2513.14007798
  Xcode:
    version: 26.0.1/17A400
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.13
    path: /usr/bin/javac
  Ruby:
    version: 3.2.6
    path: /Users/ving/.rbenv/shims/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 18.0.0
    wanted: 18.0.0
  react:
    installed: 19.0.0
    wanted: 19.0.0
  react-native:
    installed: 0.79.2
    wanted: 0.79.2
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

Re.Pack Version

5.2.1

Reproduction

none

Steps to reproduce

none

[jbroma]

Hi @npcv1999

babel-swc-loader utilizes both babel & swc and should have the most compatible output, could you please show your babel.config.js if it contains any additional stuff that might be influencing the build?

[npcv1999]

Hi @jbroma , here is my babel.config.js

const fs = require("fs");
const path = require("path");

function getDynamicAliases(srcPath) {
  const folders = fs
    .readdirSync(srcPath, { withFileTypes: true })
    .filter((dirent) => dirent.isDirectory())
    .map((dirent) => dirent.name);

  // Tạo object paths
  const paths = folders.reduce((acc, folder) => {
    acc[`@${folder}`] = `./src/${folder}`;
    return acc;
  }, {});
  return paths;
}

const ReactCompilerConfig = {
  target: "19",
};

module.exports = {
  presets: ["module:@react-native/babel-preset"],
  env: {
    production: {
      plugins: ["transform-remove-console"],
    },
  },
  plugins: [
    ["babel-plugin-react-compiler", ReactCompilerConfig],
    '@babel/plugin-syntax-jsx',
    ["transform-inline-environment-variables"],
    ["module:react-native-dotenv"],
    [
      "module-resolver",
      {
        extensions: [".tsx", ".ts", ".js", ".json"],
        alias: {
          ...getDynamicAliases(path.resolve(__dirname, "src")),
        },
      },
    ],
    "react-native-reanimated/plugin",
  ],
};

[npcv1999]

hi @jbroma , can you help me this ?

[jbroma]

@npcv1999 without reproduction I won't be able to diagnose this kind of issue - it's most likely some sort of edge case with babel / swc interop and without this exact setup I'm not able to deduce what could be the issue here.

[jbroma]

this PR makes babel-swc-loader slightly more compatible:
#1364

please see if this canary release fixes the issue you were having:
npmjs.com/package/@callstack/repack/v/5.2.5-canary-20260305211900

[swrobel]

@jbroma I'm not the OP, but was having a similar issue, and the canary version fixed it for me