[Android] Release build fails with R8: duplicate TurboModule spec classes (e.g. NativeCalendarEventModuleSpec) when New Architecture + app codegenConfig

[isinuyk]

Environment
@appzung/react-native-code-push: 11.0.3 (adjust if different)
react-native: 0.84.x (New Architecture enabled)
Android Gradle Plugin / Gradle: (your versions)
Repro: assembleDevRelease (or any release variant with minifyEnabled true / R8)

Symptom
Release build fails at :app:minify*ReleaseWithR8 with an error similar to:

R8: Type com..NativeCalendarEventModuleSpec is defined multiple times:
.../transforms/.../classes.jar:com//NativeCalendarEventModuleSpec.class
.../app/build/intermediates/.../com//NativeCalendarEventModuleSpec.class
Debug builds without R8/ProGuard often succeed.

Expected behavior
The host app should be able to use CodePush, New Architecture, app-level codegenConfig / Turbo Modules, and R8 in release without duplicate classes.

Actual behavior
R8 reports duplicate definitions of app-generated TurboModule spec classes (same package as codegenConfig.android.javaPackageName), because those classes appear both in the app compile output and in a dependency produced from this library.

Root cause (analysis)
react-native.config.js sets android.sourceDir to ./android/app.

android/app/build.gradle applies com.facebook.react when New Architecture is enabled.

React Native’s Gradle plugin registers codegen for library projects (configureCodegen(..., isLibrary = true) in ReactPlugin.kt).

For this module, findPackageJsonFile does not find android/package.json, so it resolves the host app’s package.json (with codegenConfig).

The codegen task’s onlyIf includes isLibrary, so the app’s TurboModule Java specs are generated under this library’s build/generated/source/codegen/java/... and compiled into the CodePush AAR, duplicating the same classes generated in :app.

CodePush’s own src does not appear to need these generated specs.

Suggested direction (for maintainers)
Preferred: Stop applying com.facebook.react on the CodePush library if it is not required for JNI/codegen, or restrict codegen so the library does not run host app TurboModule codegen (e.g. align with how other RN libraries avoid duplicating app specs).

Optional doc: Warn that apply plugin: "com.facebook.react" on a library under the app’s monorepo can duplicate app codegen when sourceDir is android/app and there is no intervening package.json without codegenConfig.

Minimal repro
RN 0.7x+ with New Arch on, newArchEnabled=true.
App package.json with codegenConfig (Turbo Modules) and android.javaPackageName set (e.g. com.example.app).
Install @appzung/react-native-code-push, release build with minifyEnabled true.
Observe R8 duplicate class on Native*ModuleSpec for that package.

[isinuyk]

diff --git a/android/app/build.gradle b/android/app/build.gradle
index b2eadafbb7c8dbf3fb2a6b55c8d1116843b0f2fa..9793215a15d45711be9912f1d42ca376051e6293 100644
--- a/android/app/build.gradle
+++ b/android/app/build.gradle
@@ -4,9 +4,9 @@ def isNewArchitectureEnabled() {
 
 apply plugin: "com.android.library"
 
-if (isNewArchitectureEnabled()) {
-  apply plugin: "com.facebook.react"
-}
 
 def getExtOrDefault(name) {
   return rootProject.ext.has(name) ? rootProject.ext.get(name) : project.properties["CodePush_" + name]

I was able to fix it by applying it, I'm not sure if it break anything, can you confirm it's safe?

[Minishlink]

Hello, thanks for the feedback. Will test this more thoroughly later but yes if you have no problem compiling and no crash with basic usage the rest should be safe