Fix ConcurrentModificationException in InteropUIBlockListener (#51631)

Summary:
This React Native Android fix hardens the Fabric `InteropUiBlockListener` against `ConcurrentModificationException` crashes in `willMountItems` and `didMountItems`. By iterating over a shallow copy of the UI‐block lists and catching any mid‐iteration mutations, we ensure the listener never throws during a UI frame and always clears its pending blocks.

The issue was first reported in [React Native Issue https://github.com/facebook/react-native/issues/49783](https://github.com/facebook/react-native/issues/49783), and although [React Native PR#50091](#50091) was closed and not merged, the work in that PR did make it to React Native in [commit 17da3cb](17da3cb). However, the fix didn't go far enough. We saw intermittent examples of this exception being thrown when swiping through a carousel from `react-native-reanimated-carousel`. This fix goes right to the exception site itself.

## Changelog:

[ANDROID] [FIXED] -  Hardened the Fabric `InteropUiBlockListener` against `ConcurrentModificationException` crashes in `willMountItems` and `didMountItems`

Pull Request resolved: #51631

Test Plan:
The only way to test this is to develop a standalone app that emulates what we've been seeing in our commercially available RN app. We have done extensive testing of before (intermittent crashes) and after the fix (no crashes) and things have been standing up very well for us.

Here is a the Red Box we see right at the time of the crash, before this fix:

<img width="414" alt="image" src="https://github.com/user-attachments/assets/8d1b6c6d-42f7-48a0-9574-2f05436547d4" />

And here is the beginning of the logcat crash log:

```
2025-05-07 16:01:49.212 unknown:BridgelessReact com.aura.suite                       W  ReactHost{0}.handleHostException(message = "null")
2025-05-07 16:01:49.212 unknown:ReactNative     com.aura.suite                       E  Exception in native call
                                                                                        java.util.ConcurrentModificationException
                                                                                        	at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:1111)
                                                                                        	at java.util.ArrayList$Itr.next(ArrayList.java:1064)
                                                                                        	at com.facebook.react.fabric.internal.interop.InteropUIBlockListener.willMountItems(InteropUiBlockListener.kt:72)
                                                                                        	at com.facebook.react.fabric.FabricUIManager$MountItemDispatchListener.willMountItems(FabricUIManager.java:1235)
                                                                                        	at com.facebook.react.fabric.mounting.MountItemDispatcher.dispatchMountItems(MountItemDispatcher.java:184)
                                                                                        	at com.facebook.react.fabric.mounting.MountItemDispatcher.tryDispatchMountItems(MountItemDispatcher.java:122)
                                                                                        	at com.facebook.react.fabric.FabricUIManager$3.runGuarded(FabricUIManager.java:820)
                                                                                        	at com.facebook.react.bridge.GuardedRunnable.run(GuardedRunnable.java:29)
                                                                                        	at com.facebook.react.fabric.FabricUIManager.scheduleMountItem(FabricUIManager.java:824)
                                                                                        	at com.facebook.react.fabric.FabricUIManagerBinding.reportMount(Native Method)
                                                                                        	at com.facebook.react.fabric.FabricUIManager$MountItemDispatchListener$1.run(FabricUIManager.java:1282)
                                                                                        	at android.os.Handler.handleCallback(Handler.java:959)
                                                                                        	at android.os.Handler.dispatchMessage(Handler.java:100)
                                                                                        	at android.os.Looper.loopOnce(Looper.java:232)
                                                                                        	at android.os.Looper.loop(Looper.java:317)
                                                                                        	at android.app.ActivityThread.main(ActivityThread.java:8592)
                                                                                        	at java.lang.reflect.Method.invoke(Native Method)
                                                                                        	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:580)
                                                                                        	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:878)
```

All of this goes away with this fix. We're using React Native 0.79.2 and this is the first time we've open a PR for react-native. I hope this is enough info as far as testing goes.

Can we see a 0.79.x release with this fix, please?

Reviewed By: Abbondanzo, cortinico

Differential Revision: D75594791

Pulled By: javache

fbshipit-source-id: 982ae27e89756fdb290a24b0bdfa67c2e47c04e3

Author: jkoutavas

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/internal/interop/InteropUiBlockListener.kt

@@ -9,6 +9,7 @@
 
 package com.facebook.react.fabric.internal.interop
 
+import androidx.annotation.VisibleForTesting
 import com.facebook.react.bridge.UIManager
 import com.facebook.react.bridge.UIManagerListener
 import com.facebook.react.common.annotations.UnstableReactNativeAPI
@@ -24,9 +25,9 @@ import com.facebook.react.fabric.interop.UIBlockViewResolver
  */
 @OptIn(UnstableReactNativeAPI::class)
 internal class InteropUIBlockListener : UIManagerListener {
+  @VisibleForTesting internal val beforeUIBlocks: MutableList<UIBlock> = mutableListOf()
 
-  internal val beforeUIBlocks: MutableList<UIBlock> = mutableListOf()
-  internal val afterUIBlocks: MutableList<UIBlock> = mutableListOf()
+  @VisibleForTesting internal val afterUIBlocks: MutableList<UIBlock> = mutableListOf()
 
   @Synchronized
   fun prependUIBlock(block: UIBlock) {
@@ -39,27 +40,37 @@ internal class InteropUIBlockListener : UIManagerListener {
   }
 
   override fun willMountItems(uiManager: UIManager) {
-    if (beforeUIBlocks.isEmpty()) {
+    if (uiManager !is UIBlockViewResolver) {
       return
     }
-    beforeUIBlocks.forEach {
-      if (uiManager is UIBlockViewResolver) {
-        it.execute(uiManager)
-      }
-    }
-    beforeUIBlocks.clear()
+
+    // avoid ConcurrentModificationException by iterating over a copy
+    val blocks =
+        synchronized(this) {
+          if (beforeUIBlocks.isEmpty()) {
+            return
+          }
+          beforeUIBlocks.toList().also { beforeUIBlocks.clear() }
+        }
+
+    blocks.forEach { block -> block.execute(uiManager) }
   }
 
   override fun didMountItems(uiManager: UIManager) {
-    if (afterUIBlocks.isEmpty()) {
+    if (uiManager !is UIBlockViewResolver) {
       return
     }
-    afterUIBlocks.forEach {
-      if (uiManager is UIBlockViewResolver) {
-        it.execute(uiManager)
-      }
-    }
-    afterUIBlocks.clear()
+
+    // avoid ConcurrentModificationException by iterating over a copy
+    val blocks =
+        synchronized(this) {
+          if (afterUIBlocks.isEmpty()) {
+            return
+          }
+          afterUIBlocks.toList().also { afterUIBlocks.clear() }
+        }
+
+    blocks.forEach { block -> block.execute(uiManager) }
   }
 
   override fun didDispatchMountItems(uiManager: UIManager) = didMountItems(uiManager)