Unable to run react-native app in Debug mode from Xcode

Current Behavior

When triggering a react-native app from within Xcode in Debug build configuration I get the error: Error: Unable to resolve module ./src/main from /Users/nathanjulianomeibergen/Documents/development/happynrwl/.

Expected Behavior

I’d expect the app simply to start successfully.
I believe however that this did used to work. I recently migrated to the latest NX version - 14.7.5 -, but I am not 100% sure that it used to. My approach is mostly to run the Release version in Xcode for Archiving purposes.

Why I want this?

In my real-world application I stumble upon an error when running nx run-ios myapp. For better debugging purposes the error even suggest to try running from Xcode. The Release version starts up fine, that’s why I wanted to know what is happening in Debug mode.

Steps to Reproduce

In order to reproduce simply run (as described here):

npx create-nx-workspace happynrwl \
--preset=react-native \
--appName=mobile

Now head to apps/mobile/ios/ and open Mobile.xcworkspace. Then in Xcode ‘Edit Scheme’ and make sure that the ‘Build Configuration’ is set to ‘Debug’.

Environment

Info from npx react-native info:

System:
    OS: macOS 12.6
    CPU: (8) arm64 Apple M1
    Memory: 201.17 MB / 16.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 18.9.0 - /opt/homebrew/bin/node
    Yarn: 1.22.19 - /opt/homebrew/bin/yarn
    npm: 8.19.1 - /opt/homebrew/bin/npm
    Watchman: 2022.09.05.00 - /opt/homebrew/bin/watchman
  Managers:
    CocoaPods: 1.11.3 - /opt/homebrew/bin/pod
  SDKs:
    iOS SDK:
      Platforms: iOS 14.5, DriverKit 20.4, macOS 11.3, tvOS 14.5, watchOS 7.4
    Android SDK: Not Found
  IDEs:
    Android Studio: Not Found
    Xcode: 12.5.1/12E507 - /usr/bin/xcodebuild
  Languages:
    Java: 11.0.10 - /usr/bin/javac
  npmPackages:
    @react-native-community/cli: 9.0.0 => 9.0.0
    react: 18.2.0 => 18.2.0
    react-native: 0.69.4 => 0.69.4
    react-native-macos: Not Found
  npmGlobalPackages:
    *react-native*: Not Found

[curthipster]

I just tested with 14.7.6, which includes https://github.com/nrwl/nx/pull/11971. I was able to build and run in XCode.

Edit: it worked at first, and now it’s not. I can’t tell what’s changed. Argh.

I figured out what the difference is. If metro is already running when launching the app from within XCode, then it runs. If XCode launches metro, then it results in Error: Unable to resolve module ./src/main...

[chrismcleod]

I think this happens bc of this

if you echo $THIS_PATH in launchPackager.command, it’s the root of the monorepo, not the apps/appName directory. This is probably bc of the symlinked node_modules folder.

I added/used a custom launch command file in the root of the app folder and it works.

apps/MyCoolApp/launch.command

cd "$(dirname "$0")" && yarn nx start "MyCoolApp"

Update the Xcode launch script: open "$SRCROOT/../launch.command" || echo "Can't start packager automatically"

Probably not the best long-term solution.