Fix Android Fabric Native Animated null prop crash

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/mounting/SurfaceMountingManager.kt

@@ -626,13 +626,14 @@ internal constructor(
   public fun storeSynchronousMountPropsOverride(reactTag: Int, props: ReadableMap): Unit {
     if (ReactNativeFeatureFlags.overrideBySynchronousMountPropsAtMountingAndroid()) {
       val propsMap = getMapFromPropsReadableMap(props)
-      var synchronousMountProps = tagToSynchronousMountProps[reactTag]
-      if (synchronousMountProps != null) {
-        synchronousMountProps.putAll(propsMap)
+      val synchronousMountProps = tagToSynchronousMountProps[reactTag] ?: mutableMapOf()
+      removeNullTransformAndOpacityPropsFromPropsReadableMap(props, synchronousMountProps)
+      synchronousMountProps.putAll(propsMap)
+      if (synchronousMountProps.isEmpty()) {
+        tagToSynchronousMountProps.remove(reactTag)
       } else {
-        synchronousMountProps = propsMap
+        tagToSynchronousMountProps[reactTag] = synchronousMountProps
       }
-      tagToSynchronousMountProps[reactTag] = synchronousMountProps
     }
   }
 
@@ -1332,7 +1333,10 @@ internal constructor(
       for ((propKey, propValue) in patchMap) {
         if (outputReadableMap.hasKey(propKey)) {
           if (propKey == PROP_TRANSFORM) {
-            assert(outputReadableMap.getType(propKey) == ReadableType.Array && propValue is List<*>)
+            val outputType = outputReadableMap.getType(propKey)
+            assert(
+                (outputType == ReadableType.Array || outputType == ReadableType.Null) &&
+                    propValue is List<*>)
             val array = WritableNativeArray()
             for (item in propValue as List<*>) {
               if (item is Map<*, *>) {
@@ -1350,7 +1354,10 @@ internal constructor(
             }
             outputReadableMap.putArray(propKey, array)
           } else if (propKey == PROP_OPACITY) {
-            assert(outputReadableMap.getType(propKey) == ReadableType.Number && propValue is Number)
+            val outputType = outputReadableMap.getType(propKey)
+            assert(
+                (outputType == ReadableType.Number || outputType == ReadableType.Null) &&
+                    propValue is Number)
             outputReadableMap.putDouble(propKey, (propValue as Number).toDouble())
           }
         }
@@ -1387,6 +1394,22 @@ internal constructor(
       return outputMap
     }
 
+    private fun removeNullTransformAndOpacityPropsFromPropsReadableMap(
+        readableMap: ReadableMap,
+        outputMap: MutableMap<String, Any>,
+    ) {
+      // Native Animated uses synchronous null updates to restore animated-managed props.
+      // Keep this scoped to props stored by this override path today.
+      if (readableMap.hasKey(PROP_TRANSFORM) &&
+          readableMap.getType(PROP_TRANSFORM) == ReadableType.Null) {
+        outputMap.remove(PROP_TRANSFORM)
+      }
+      if (readableMap.hasKey(PROP_OPACITY) &&
+          readableMap.getType(PROP_OPACITY) == ReadableType.Null) {
+        outputMap.remove(PROP_OPACITY)
+      }
+    }
+
     // prevents unchecked conversion warn of the <ViewGroup> type
     private fun getViewGroupManager(viewState: ViewState): IViewGroupManager<View> {
       val viewManager =

packages/react-native/ReactAndroid/src/test/java/com/facebook/react/fabric/SurfaceMountingManagerSynchronousMountPropsTest.kt

@@ -10,15 +10,17 @@
 package com.facebook.react.fabric
 
 import com.facebook.react.ReactRootView
+import com.facebook.react.bridge.JavaOnlyArray
 import com.facebook.react.bridge.JavaOnlyMap
+import com.facebook.react.bridge.ReadableArray
 import com.facebook.react.bridge.ReactTestHelper
 import com.facebook.react.fabric.mounting.MountingManager
-import com.facebook.react.fabric.mounting.MountingManager.MountItemExecutor
 import com.facebook.react.fabric.mounting.SurfaceMountingManager
 import com.facebook.react.internal.featureflags.ReactNativeFeatureFlagsForTests
 import com.facebook.react.uimanager.ThemedReactContext
 import com.facebook.react.uimanager.ViewManager
 import com.facebook.react.uimanager.ViewManagerRegistry
+import com.facebook.react.views.view.ReactViewGroup
 import com.facebook.react.views.view.ReactViewManager
 import com.facebook.testutils.shadows.ShadowNativeLoader
 import com.facebook.testutils.shadows.ShadowNativeMap
@@ -67,8 +69,8 @@ class SurfaceMountingManagerSynchronousMountPropsTest {
     themedReactContext = ThemedReactContext(reactContext, reactContext, null, -1)
     mountingManager =
         MountingManager(
-            ViewManagerRegistry(listOf<ViewManager<*, *>>(ReactViewManager())),
-            MountItemExecutor {},
+            ViewManagerRegistry(listOf<ViewManager<*, *>>(TestReactViewManager())),
+            {},
         )
   }
 
@@ -83,6 +85,25 @@ class SurfaceMountingManagerSynchronousMountPropsTest {
     smm.addViewAt(surfaceId, tag, 0)
   }
 
+  private class TestReactViewManager : ReactViewManager() {
+    override fun setTransformProperty(
+        view: ReactViewGroup,
+        transforms: ReadableArray?,
+        transformOrigin: ReadableArray?,
+    ) {
+      view.translationY = 0.0f
+      if (transforms == null) {
+        return
+      }
+      for (i in 0..<transforms.size()) {
+        val transform = transforms.getMap(i) ?: continue
+        if (transform.hasKey("translateY")) {
+          view.translationY = transform.getDouble("translateY").toFloat()
+        }
+      }
+    }
+  }
+
   /** Stored synchronous opacity should override a stale Fabric mount update. */
   @Test
   fun storeSynchronousProps_overridesStaleOpacityInUpdateProps() {
@@ -100,7 +121,7 @@ class SurfaceMountingManagerSynchronousMountPropsTest {
     assertThat(smm.getView(tag).alpha).isEqualTo(0.3f)
   }
 
-  /** Multiple storeSynchronousMountPropsOverride calls should merge — later values win. */
+  /** Multiple storeSynchronousMountPropsOverride calls should merge; later values win. */
   @Test
   fun storeSynchronousProps_mergesMultipleCalls() {
     val smm = startSurface()
@@ -137,6 +158,80 @@ class SurfaceMountingManagerSynchronousMountPropsTest {
     assertThat(smm.getView(tag).alpha).isEqualTo(0.2f)
   }
 
+  /** A null Fabric prop update should not clear the stored synchronous opacity override. */
+  @Test
+  fun updateProps_withNullOpacity_keepsStoredSynchronousProp() {
+    val smm = startSurface()
+    val tag = 42
+    createAndAttachView(smm, tag)
+
+    smm.storeSynchronousMountPropsOverride(tag, JavaOnlyMap.of("opacity", 0.3))
+    smm.updatePropsSynchronously(tag, JavaOnlyMap.of("opacity", 0.3))
+    assertThat(smm.getView(tag).alpha).isEqualTo(0.3f)
+
+    smm.updateProps(tag, JavaOnlyMap.of("opacity", null))
+
+    assertThat(smm.getView(tag).alpha).isEqualTo(0.3f)
+  }
+
+  /** A synchronous null update should clear the stored synchronous opacity override. */
+  @Test
+  fun updatePropsSynchronously_withNullOpacity_removesStoredSynchronousProp() {
+    val smm = startSurface()
+    val tag = 42
+    createAndAttachView(smm, tag)
+
+    smm.storeSynchronousMountPropsOverride(tag, JavaOnlyMap.of("opacity", 0.3))
+    smm.updatePropsSynchronously(tag, JavaOnlyMap.of("opacity", 0.3))
+    assertThat(smm.getView(tag).alpha).isEqualTo(0.3f)
+
+    smm.storeSynchronousMountPropsOverride(tag, JavaOnlyMap.of("opacity", null))
+    smm.updatePropsSynchronously(tag, JavaOnlyMap.of("opacity", null))
+    assertThat(smm.getView(tag).alpha).isEqualTo(1.0f)
+
+    smm.updateProps(tag, JavaOnlyMap.of("opacity", null))
+
+    assertThat(smm.getView(tag).alpha).isEqualTo(1.0f)
+  }
+
+  /** A null Fabric prop update should not clear the stored synchronous transform override. */
+  @Test
+  fun updateProps_withNullTransform_keepsStoredSynchronousProp() {
+    val smm = startSurface()
+    val tag = 42
+    val transform = JavaOnlyArray.of(JavaOnlyMap.of("translateY", 40.0))
+    createAndAttachView(smm, tag)
+
+    smm.storeSynchronousMountPropsOverride(tag, JavaOnlyMap.of("transform", transform))
+    smm.updatePropsSynchronously(tag, JavaOnlyMap.of("transform", transform))
+    assertThat(smm.getView(tag).translationY).isEqualTo(40.0f)
+
+    smm.updateProps(tag, JavaOnlyMap.of("transform", null))
+
+    assertThat(smm.getView(tag).translationY).isEqualTo(40.0f)
+  }
+
+  /** A synchronous null update should clear the stored synchronous transform override. */
+  @Test
+  fun updatePropsSynchronously_withNullTransform_removesStoredSynchronousProp() {
+    val smm = startSurface()
+    val tag = 42
+    val transform = JavaOnlyArray.of(JavaOnlyMap.of("translateY", 40.0))
+    createAndAttachView(smm, tag)
+
+    smm.storeSynchronousMountPropsOverride(tag, JavaOnlyMap.of("transform", transform))
+    smm.updatePropsSynchronously(tag, JavaOnlyMap.of("transform", transform))
+    assertThat(smm.getView(tag).translationY).isEqualTo(40.0f)
+
+    smm.storeSynchronousMountPropsOverride(tag, JavaOnlyMap.of("transform", null))
+    smm.updatePropsSynchronously(tag, JavaOnlyMap.of("transform", null))
+    assertThat(smm.getView(tag).translationY).isEqualTo(0.0f)
+
+    smm.updateProps(tag, JavaOnlyMap.of("transform", null))
+
+    assertThat(smm.getView(tag).translationY).isEqualTo(0.0f)
+  }
+
   /**
    * When a view is deleted, stored synchronous props should be cleaned up. A recreated view with
    * the same tag should not be affected by the old stored props.