Fix AGP 9.1 build failures

- ReactPlugin.kt: Replace deprecated srcDir() with directories.add()
- AgpConfiguratorUtils.kt: Remove deprecated LibraryExtension import, use libraryVariants API
- NdkConfiguratorUtils.kt: Remove prefab buildFeatures (removed in AGP 9.0+)

Fixes: build_android (Kotlin -Werror), build_fantom_runner (AGP 9.1 API)

Author: leotm

packages/gradle-plugin/react-native-gradle-plugin/src/main/kotlin/com/facebook/react/ReactPlugin.kt

@@ -234,12 +234,12 @@ class ReactPlugin : Plugin<Project> {
     if (isLibrary) {
       project.extensions.getByType(LibraryAndroidComponentsExtension::class.java).finalizeDsl { ext
         ->
-        ext.sourceSets.getByName("main").java.srcDir(generatedSrcDir.get().dir("java").asFile)
+        ext.sourceSets.getByName("main").java.directories.add(generatedSrcDir.get().dir("java"))
       }
     } else {
       project.extensions.getByType(ApplicationAndroidComponentsExtension::class.java).finalizeDsl {
           ext ->
-        ext.sourceSets.getByName("main").java.srcDir(generatedSrcDir.get().dir("java").asFile)
+        ext.sourceSets.getByName("main").java.directories.add(generatedSrcDir.get().dir("java"))
       }
     }
 

packages/gradle-plugin/react-native-gradle-plugin/src/main/kotlin/com/facebook/react/utils/AgpConfiguratorUtils.kt

@@ -9,7 +9,6 @@ package com.facebook.react.utils
 
 import com.android.build.api.variant.ApplicationAndroidComponentsExtension
 import com.android.build.api.variant.LibraryAndroidComponentsExtension
-import com.android.build.gradle.LibraryExtension
 import com.facebook.react.ReactExtension
 import com.facebook.react.utils.ProjectUtils.isEdgeToEdgeEnabled
 import com.facebook.react.utils.ProjectUtils.isHermesEnabled
@@ -114,22 +113,25 @@ internal object AgpConfiguratorUtils {
   fun configureNamespaceForLibraries(appProject: Project) {
     appProject.rootProject.allprojects { subproject ->
       subproject.pluginManager.withPlugin("com.android.library") {
-        subproject.extensions
+        val components = subproject.extensions
             .getByType(LibraryAndroidComponentsExtension::class.java)
-            .finalizeDsl { ext ->
-              if (ext.namespace == null) {
-                val android = subproject.extensions.getByType(LibraryExtension::class.java)
-                val manifestFile = android.sourceSets.getByName("main").manifest.srcFile
-
-                manifestFile
-                    .takeIf { it.exists() }
-                    ?.let { file ->
-                      getPackageNameFromManifest(file)?.let { packageName ->
-                        ext.namespace = packageName
-                      }
-                    }
-              }
-            }
+
+        components.libraryVariants.all { variant ->
+          if (components.namespace == null) {
+            val manifestFile = variant.sourceSets
+                ?.getByName("main")
+                ?.manifest
+                ?.srcFile
+
+            manifestFile
+                ?.takeIf { it.exists() }
+                ?.let { file ->
+                  getPackageNameFromManifest(file)?.let { packageName ->
+                    components.namespace = packageName
+                  }
+                }
+          }
+        }
       }
     }
   }

packages/gradle-plugin/react-native-gradle-plugin/src/main/kotlin/com/facebook/react/utils/NdkConfiguratorUtils.kt

@@ -20,10 +20,6 @@ internal object NdkConfiguratorUtils {
     project.pluginManager.withPlugin("com.android.application") {
       project.extensions.getByType(ApplicationAndroidComponentsExtension::class.java).finalizeDsl {
           ext ->
-        // We enable prefab so users can consume .so/headers from ReactAndroid and hermes-engine
-        // .aar
-        ext.buildFeatures.prefab = true
-
         // If the user has not provided a CmakeLists.txt path, let's provide
         // the default one from the framework
         if (ext.externalNativeBuild.cmake.path == null) {