build backwards compat API for runtime pointer

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/runtime/BridgelessReactContext.java

@@ -12,6 +12,7 @@
 import com.facebook.react.bridge.Arguments;
 import com.facebook.react.bridge.Callback;
 import com.facebook.react.bridge.CatalystInstance;
+import com.facebook.react.bridge.JavaScriptContextHolder;
 import com.facebook.react.bridge.JavaScriptModule;
 import com.facebook.react.bridge.JavaScriptModuleRegistry;
 import com.facebook.react.bridge.NativeArray;
@@ -163,6 +164,13 @@ public Collection<NativeModule> getNativeModules() {
     return mReactHost.getRuntimeExecutor();
   }
 
+  @Override
+  @FrameworkAPI
+  @UnstableReactNativeAPI
+  public @Nullable JavaScriptContextHolder getJavaScriptContextHolder() {
+    return mReactHost.getJavaScriptContextHolder();
+  }
+
   @Override
   public void handleException(Exception e) {
     mReactHost.handleHostException(e);

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/runtime/ReactHostImpl.java

@@ -29,6 +29,7 @@
 import com.facebook.react.ReactInstanceEventListener;
 import com.facebook.react.bridge.Callback;
 import com.facebook.react.bridge.JSBundleLoader;
+import com.facebook.react.bridge.JavaScriptContextHolder;
 import com.facebook.react.bridge.MemoryPressureListener;
 import com.facebook.react.bridge.NativeArray;
 import com.facebook.react.bridge.NativeModule;
@@ -599,6 +600,15 @@ RuntimeExecutor getRuntimeExecutor() {
     return null;
   }
 
+  @Nullable
+  JavaScriptContextHolder getJavaScriptContextHolder() {
+    final ReactInstance reactInstance = mReactInstanceTaskRef.get().getResult();
+    if (reactInstance != null) {
+      return reactInstance.getJavaScriptContextHolder();
+    }
+    return null;
+  }
+
   /* package */
   DefaultHardwareBackBtnHandler getDefaultBackButtonHandler() {
     return () -> {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/runtime/ReactInstance.java

@@ -20,6 +20,7 @@
 import com.facebook.react.bridge.Arguments;
 import com.facebook.react.bridge.JSBundleLoader;
 import com.facebook.react.bridge.JSBundleLoaderDelegate;
+import com.facebook.react.bridge.JavaScriptContextHolder;
 import com.facebook.react.bridge.LifecycleEventListener;
 import com.facebook.react.bridge.NativeArray;
 import com.facebook.react.bridge.NativeMap;
@@ -95,6 +96,8 @@ final class ReactInstance {
   private final JavaTimerManager mJavaTimerManager;
   private final BridgelessViewManagerResolver mViewManagerResolver;
 
+  private JavaScriptContextHolder mJavaScriptContextHolder;
+
   @DoNotStrip @Nullable private ComponentNameResolverManager mComponentNameResolverManager;
   @DoNotStrip @Nullable private UIConstantsProviderManager mUIConstantsProviderManager;
 
@@ -181,6 +184,8 @@ public void onHostDestroy() {
             bindingsInstaller,
             isProfiling);
 
+    mJavaScriptContextHolder = new JavaScriptContextHolder(getJavaScriptContext());
+
     // Set up TurboModules
     Systrace.beginSection(
         Systrace.TRACE_TAG_REACT_JAVA_BRIDGE, "ReactInstance.initialize#initTurboModules");
@@ -430,6 +435,10 @@ public Collection<NativeModule> getNativeModules() {
     mFabricUIManager.stopSurface(surface.getSurfaceHandler());
   }
 
+  /* package */ JavaScriptContextHolder getJavaScriptContextHolder() {
+    return mJavaScriptContextHolder;
+  }
+
   /* --- Lifecycle methods --- */
   @ThreadConfined("ReactHost")
   /* package */ void destroy() {
@@ -440,6 +449,7 @@ public Collection<NativeModule> getNativeModules() {
     mHybridData.resetNative();
     mComponentNameResolverManager = null;
     mUIConstantsProviderManager = null;
+    mJavaScriptContextHolder.clear();
   }
 
   /* --- Native methods --- */
@@ -475,6 +485,8 @@ private native HybridData initHybrid(
 
   private native RuntimeScheduler getRuntimeScheduler();
 
+  private native long getJavaScriptContext();
+
   /* package */ native void callFunctionOnModule(
       String moduleName, String methodName, NativeArray args);
 

packages/react-native/ReactAndroid/src/main/jni/react/runtime/jni/JReactInstance.cpp

@@ -201,6 +201,10 @@ void JReactInstance::handleMemoryPressureJs(jint level) {
   instance_->handleMemoryPressureJs(level);
 }
 
+jlong JReactInstance::getJavaScriptContext() {
+  return (jlong)(intptr_t)instance_->getJavaScriptContext();
+}
+
 void JReactInstance::registerNatives() {
   registerHybrid({
       makeNativeMethod("initHybrid", JReactInstance::initHybrid),
@@ -230,6 +234,8 @@ void JReactInstance::registerNatives() {
           "registerSegmentNative", JReactInstance::registerSegment),
       makeNativeMethod(
           "handleMemoryPressureJs", JReactInstance::handleMemoryPressureJs),
+      makeNativeMethod(
+          "getJavaScriptContext", JReactInstance::getJavaScriptContext),
   });
 }
 

packages/react-native/ReactAndroid/src/main/jni/react/runtime/jni/JReactInstance.h

@@ -105,6 +105,8 @@ class JReactInstance : public jni::HybridClass<JReactInstance> {
       nativeMethodCallInvokerHolder_;
   jni::global_ref<JReactExceptionManager::javaobject> jReactExceptionManager_;
   jni::global_ref<JBindingsInstaller::javaobject> jBindingsInstaller_;
+
+  jlong getJavaScriptContext();
 };
 
 } // namespace facebook::react

packages/react-native/ReactCommon/react/runtime/ReactInstance.cpp

@@ -465,4 +465,8 @@ void ReactInstance::handleMemoryPressureJs(int pressureLevel) {
   }
 }
 
+void* ReactInstance::getJavaScriptContext() {
+  return &runtime_->getRuntime();
+}
+
 } // namespace facebook::react

packages/react-native/ReactCommon/react/runtime/ReactInstance.h

@@ -71,6 +71,8 @@ class ReactInstance final : private jsinspector_modern::InstanceTargetDelegate {
    */
   void unregisterFromInspector();
 
+  void* getJavaScriptContext();
+
  private:
   std::shared_ptr<JSRuntime> runtime_;
   std::shared_ptr<MessageQueueThread> jsMessageQueueThread_;