fix: update JS bundle loading for OTA reload to prevent app loop

Author: vadymv-mendix

android/src/main/java/com/mendix/mendixnative/MendixReactApplication.kt

@@ -4,7 +4,16 @@ import android.app.Application
 import com.facebook.react.ReactHost
 import com.facebook.react.ReactNativeHost
 import com.facebook.react.ReactPackage
+import com.facebook.react.bridge.JSBundleLoader
+import com.facebook.react.bridge.JSBundleLoaderDelegate
+import com.facebook.react.common.annotations.UnstableReactNativeAPI
+import com.facebook.react.defaults.DefaultComponentsRegistry
+import com.facebook.react.defaults.DefaultReactHostDelegate
+import com.facebook.react.defaults.DefaultTurboModuleManagerDelegate
 import com.facebook.react.devsupport.interfaces.RedBoxHandler
+import com.facebook.react.fabric.ComponentFactory
+import com.facebook.react.runtime.ReactHostImpl
+import com.facebook.react.runtime.hermes.HermesInstance
 import com.facebook.react.soloader.OpenSourceMergedSoMapping
 import com.facebook.soloader.SoLoader
 import com.mendix.mendixnative.error.ErrorHandler
@@ -16,7 +25,6 @@ import com.mendix.mendixnative.react.splash.MendixSplashScreenPresenter
 import com.mendixnative.MendixNativePackage
 import java.util.*
 import com.facebook.react.defaults.DefaultNewArchitectureEntryPoint.load
-import com.facebook.react.defaults.DefaultReactHost.getDefaultReactHost
 
 import com.facebook.react.defaults.DefaultReactNativeHost
 
@@ -56,8 +64,51 @@ abstract class MendixReactApplication : Application(), MendixApplication, ErrorH
     override val isHermesEnabled: Boolean = true
   }
 
-  override val reactHost: ReactHost
-    get() = getDefaultReactHost(applicationContext, reactNativeHost)
+  // Build the bridgeless ReactHost ourselves (instead of DefaultReactHost.getDefaultReactHost)
+  // so we can supply a *dynamic* JSBundleLoader. reactHost.reload() destroys and recreates the
+  // React instance, re-invoking this loader's loadScript() on every reload. By resolving
+  // getJSBundleFile() inside loadScript() each time, a freshly-deployed OTA bundle is picked up
+  // automatically — without this the loader is fixed at construction time and the app loops:
+  // download -> deploy -> reload -> same old bundle. `by lazy` keeps it a single host instance.
+  @OptIn(UnstableReactNativeAPI::class)
+  override val reactHost: ReactHost by lazy {
+    val dynamicBundleLoader = object : JSBundleLoader() {
+      override fun loadScript(delegate: JSBundleLoaderDelegate): String {
+        val bundle = jsBundleFile
+        if (bundle != null) {
+          if (bundle.startsWith("assets://")) {
+            delegate.loadScriptFromAssets(assets, bundle, true)
+          } else {
+            delegate.loadScriptFromFile(bundle, bundle, false)
+          }
+          return bundle
+        }
+        val defaultBundle = "assets://index.android.bundle"
+        delegate.loadScriptFromAssets(assets, defaultBundle, true)
+        return defaultBundle
+      }
+    }
+
+    val hostPackages: MutableList<ReactPackage> = ArrayList(this@MendixReactApplication.packages)
+    applyInternalPackageAugmentations(hostPackages)
+
+    val delegate = DefaultReactHostDelegate(
+      jsMainModulePath = "index",
+      jsBundleLoader = dynamicBundleLoader,
+      reactPackages = hostPackages,
+      jsRuntimeFactory = HermesInstance(),
+      turboModuleManagerDelegateBuilder = DefaultTurboModuleManagerDelegate.Builder(),
+    )
+    val componentFactory = ComponentFactory()
+    DefaultComponentsRegistry.register(componentFactory)
+    ReactHostImpl(
+      applicationContext,
+      delegate,
+      componentFactory,
+      true /* allowPackagerServerAccess */,
+      useDeveloperSupport,
+    )
+  }
 
   /**
    * Apply internal augmentations to packages (e.g., attach presenters) without instantiating

android/src/main/java/com/mendix/mendixnative/react/NativeReloadHandler.kt

@@ -4,12 +4,8 @@ import android.os.Handler
 import android.os.Looper
 import com.facebook.common.logging.FLog
 import com.facebook.react.ReactApplication
-import com.facebook.react.bridge.JSBundleLoader
 import com.facebook.react.bridge.ReactApplicationContext
-import com.mendix.mendixnative.MendixApplication
 import com.mendix.mendixnative.activity.LaunchScreenHandler
-import com.mendix.mendixnative.util.ReflectionUtils
-import com.op.sqlite.OPSQLiteModule
 
 class NativeReloadHandler(val context: ReactApplicationContext) {
 
@@ -24,14 +20,18 @@ class NativeReloadHandler(val context: ReactApplicationContext) {
                 javaClass,
                 "Activity does not implement LaunchScreenHandler, skipping showing launch screen"
             )
-        handleJSBundleLoading()
         reloadWithoutState()
     }
 
     fun exitApp() {
         context.currentActivity?.finishAffinity()
     }
 
+    // In the New Architecture (Bridgeless), reactHost.reload() destroys and recreates the
+    // React instance, which re-invokes the JSBundleLoader provided to ReactHostImpl at
+    // construction time. MendixReactApplication supplies a *dynamic* JSBundleLoader whose
+    // loadScript() calls MendixReactApplication.getJSBundleFile() on every reload, so OTA
+    // bundle changes are picked up automatically — no manual bundle swapping is needed.
     private fun reloadWithoutState() {
         val reactHost = (context.applicationContext as? ReactApplication)?.reactHost
         postOnMainThread {
@@ -48,39 +48,4 @@ class NativeReloadHandler(val context: ReactApplicationContext) {
             cb.invoke()
         }
     }
-
-    private fun handleJSBundleLoading() {
-        val bundle = (context.applicationContext as MendixApplication).jsBundleFile
-
-        val latestJSBundleLoader = if (bundle != null) {
-            getAssetLoader(bundle)
-        } else {
-            getAssetLoader("assets://index.android.bundle")
-        } ?: return
-
-        // New Architecture (Bridgeless): on reload, ReactHostImpl loads the bundle from
-        // its ReactHostDelegate.jsBundleLoader, which is captured once at host-creation
-        // time and never re-consults getJSBundleFile(). Without updating it here, a warm
-        // reload keeps loading the original bundle, so a freshly-deployed OTA bundle is
-        // never picked up and the app loops: download -> deploy -> reload -> same bundle.
-        val reactHost = (context.applicationContext as? ReactApplication)?.reactHost ?: return
-        try {
-            val delegate = ReflectionUtils.getField<Any>(reactHost, "mReactHostDelegate")
-            ReflectionUtils.setField(delegate, "jsBundleLoader", latestJSBundleLoader)
-        } catch (e: Exception) {
-            FLog.e(javaClass, "Failed to update JS bundle loader for OTA reload", e)
-        }
-    }
-
-    private fun getAssetLoader(bundle: String): JSBundleLoader? {
-        return when {
-            bundle.startsWith("assets://") -> JSBundleLoader.createAssetLoader(
-                context,
-                bundle,
-                false
-            )
-
-            else -> JSBundleLoader.createFileLoader(bundle)
-        }
-    }
 }