UIManagerModule.addUIBlock not working in New Architecture

[joemun]

Someone had filed this issue over in the RN repo here: facebook/react-native#34764
I'm picking up where that left off, as I'm also experiencing this issue.

It looks like UIManagerModule.addUIBlock() doesn't work when New Arch is enabled. The callback is not called.

Is this expected? For New Architecture, was addUIBlock() replaced with another API? (I did find UiThreadUtil.runOnUiThread(), but I'm not sure if that's meant to be a suitable replacement...)

I've created a repro based on the RN Reproducer app here: https://github.com/joemun/uimanagermodule-adduiblock-test
The client calls the Turbo Module function, which is then supposed to resolve the promise in the addUIBlock() callback, but the callback is not called. If newArchEnabled is then set to false, the callback is called.

[arushikesarwani94]

Apologies for the delayed response. Yes, that's correct for New Arch UIManagerModule.addUIBlock() returns null on Bridgeless.

The replacement API added for Backwards Compatibility in Bridgeless is
https://github.com/facebook/react-native/blob/2483c63017b0d47c377bf67cb7c597e2d7e57897/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/FabricUIManager.java#L104

Sample fix PRs : expo/expo#29500 react-native-maps/react-native-maps#5061