Metro bundle extremely slow and gets stuck with babel v7.17.x

Description

I had a huge issue bundling the app for development and production as soon as I updated the following packages to the latest version:

"@babel/core": "7.16.12",
"@babel/plugin-proposal-decorators": "7.16.7",
"@babel/runtime": "7.16.7",
"babel-jest": "27.5.1",
"metro-react-native-babel-preset": "0.67.0",

Basically, one of the mentioned packages is causing metro to bundle extremely slow and finally get stuck at approximately 90%. After I reverted the package.json back to an older version, it still didn’t help because of the ^. I had to remove ^ from the packages I mentioned, and it was back to normal.

I’m guessing it’s a babel issue (I also updated React Native to 0.67.3), but I think you guys should know, I spent all day yesterday trying to resolve this (I also looked on here) without any luck.

Also, after all of that I was required to install 2 additional packages:

"@babel/plugin-transform-arrow-functions": "7.16.7",
"@babel/plugin-transform-shorthand-properties": "7.16.7",

Version

0.67.3

Output of npx react-native info

System:
    OS: macOS 12.2.1
    CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
    Memory: 606.40 MB / 16.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 16.14.0 - /usr/local/bin/node
    Yarn: 1.22.17 - /usr/local/bin/yarn
    npm: 8.5.2 - /usr/local/bin/npm
    Watchman: 2022.02.21.00 - /usr/local/bin/watchman
  Managers:
    CocoaPods: 1.11.2 - /usr/local/bin/pod
  SDKs:
    iOS SDK:
      Platforms: DriverKit 21.2, iOS 15.2, macOS 12.1, tvOS 15.2, watchOS 8.3
    Android SDK:
      API Levels: 30, 31
      Build Tools: 30.0.2, 31.0.0, 32.0.0
      System Images: android-30 | Google Play Intel x86 Atom
      Android NDK: Not Found
  IDEs:
    Android Studio: Bumblebee 2021.1.1 Patch 2 Bumblebee 2021.1.1 Patch 2
    Xcode: 13.2.1/13C100 - /usr/bin/xcodebuild
  Languages:
    Java: 1.8.0_292 - /usr/bin/javac
  npmPackages:
    @react-native-community/cli: Not Found
    react: 17.0.2 => 17.0.2
    react-native: 0.67.3 => 0.67.3
    react-native-macos: Not Found
  npmGlobalPackages:
    *react-native*: Not Found

Steps to reproduce

Running npx react-native start after updating all the packages to the latest version.

Snack, code example, screenshot, or link to a repository

No response

[renchap]

This seems to only happen for iOS release builds for me, which seems weird.

Metro takes about 40 seconds to build the bundle for Android release builds, but takes about 10 minutes for the iOS release builds. Development build times are normal.

Can this help to narrow the possible cause?

[efstathiosntonas]

Thanks @milos201, it took us 2 days to find out what was going on, hopefully this gets fixed soon as it’s extremely hard to spot the issue.