Add runtime validation of Props 2.0 output (#54461)

Summary:

Compare the output from Props 1.5 with Props 2.0 to detect any missing props in the output coming from Props 2.0.

The comparison doesn't run for initial mounts due to Props 1.5 not using the default property values to generate a diff, which is obviously leading to more properties being in the Props 1.5 output that aren't necessary.

Changelog: [Internal]

Differential Revision: D86577390

Author: Nick Lefever

packages/react-native/ReactAndroid/src/main/jni/react/fabric/FabricMountingManager.cpp

@@ -54,6 +54,79 @@ void FabricMountingManager::onSurfaceStop(SurfaceId surfaceId) {
 
 namespace {
 
+#ifdef REACT_NATIVE_DEBUG
+// List of layout-only props extracted from ViewProps.kt used to filter out
+// component props from Props 1.5 to validate the Props 2.0 output
+inline bool isLayoutOnlyProp(const std::string& propName) {
+  static const std::unordered_set<std::string> layoutOnlyProps = {
+      // Flexbox Alignment
+      "alignItems",
+      "alignSelf",
+      "alignContent",
+
+      // Flexbox Properties
+      "flex",
+      "flexBasis",
+      "flexDirection",
+      "flexGrow",
+      "flexShrink",
+      "flexWrap",
+      "justifyContent",
+
+      // Gaps
+      "rowGap",
+      "columnGap",
+      "gap",
+
+      // Display & Position
+      "display",
+      "position",
+
+      // Positioning
+      "right",
+      "top",
+      "bottom",
+      "left",
+      "start",
+      "end",
+
+      // Dimensions
+      "width",
+      "height",
+      "minWidth",
+      "maxWidth",
+      "minHeight",
+      "maxHeight",
+
+      // Margins
+      "margin",
+      "marginVertical",
+      "marginHorizontal",
+      "marginLeft",
+      "marginRight",
+      "marginTop",
+      "marginBottom",
+      "marginStart",
+      "marginEnd",
+
+      // Paddings
+      "padding",
+      "paddingVertical",
+      "paddingHorizontal",
+      "paddingLeft",
+      "paddingRight",
+      "paddingTop",
+      "paddingBottom",
+      "paddingStart",
+      "paddingEnd",
+
+      // Other
+      "collapsable",
+  };
+  return layoutOnlyProps.count(propName) > 0;
+}
+#endif
+
 inline int getIntBufferSizeForType(CppMountItem::Type mountItemType) {
   switch (mountItemType) {
     case CppMountItem::Type::Create:
@@ -232,8 +305,29 @@ jni::local_ref<jobject> getProps(
       strcmp(
           newShadowView.componentName,
           newProps->getDiffPropsImplementationTarget()) == 0) {
-    return ReadableNativeMap::newObjectCxxArgs(
-        newProps->getDiffProps(oldProps));
+    auto diff = newProps->getDiffProps(oldProps);
+
+#ifdef REACT_NATIVE_DEBUG
+    if (oldProps != nullptr) {
+      auto controlDiff =
+          diffDynamicProps(oldProps->rawProps, newProps->rawProps);
+
+      for (const auto& [prop, value] : controlDiff.items()) {
+        if (diff.count(prop) == 0) {
+          // Skip layout-only props since they are not included in Props 2.0
+          if (!isLayoutOnlyProp(prop.asString())) {
+            LOG(ERROR) << "Props diff validation failed: Props 1.5 has prop '"
+                       << prop.asString()
+                       << "' = " << (value != nullptr ? value : "NULL")
+                       << " that Props 2.0 doesn't have for component "
+                       << newShadowView.componentName;
+          }
+        }
+      }
+    }
+#endif
+
+    return ReadableNativeMap::newObjectCxxArgs(std::move(diff));
   }
   if (ReactNativeFeatureFlags::enableAccumulatedUpdatesInRawPropsAndroid()) {
     if (oldProps == nullptr) {