HHH-20356 HHH-19020 NPE in ClassPropertyHolder#addPropertyToMappedSuperclass method

Co-authored-by: Marco Belladelli <marcobladel@gmail.com>

Author: dreab8

hibernate-core/src/main/java/org/hibernate/boot/model/internal/EmbeddableBinder.java

@@ -68,6 +68,7 @@
 import static org.hibernate.boot.model.internal.BinderHelper.getRelativePath;
 import static org.hibernate.boot.model.internal.BinderHelper.hasToOneAnnotation;
 import static org.hibernate.boot.model.internal.HCANNHelper.findContainingAnnotations;
+import static org.hibernate.boot.model.internal.InheritanceState.getSuperclassInheritanceState;
 import static org.hibernate.boot.model.internal.PropertyBinder.addElementsOfClass;
 import static org.hibernate.boot.model.internal.PropertyBinder.processElementAnnotations;
 import static org.hibernate.boot.model.internal.PropertyBinder.processId;
@@ -393,6 +394,14 @@ static Component fillEmbeddable(
 					context
 			);
 		}
+		else {
+			// We need to register ancestor @MappedSuperclass metadata even for embedded types of classes
+			// that are not annotated as @Embeddable (i.e. that don't have an inheritance state)
+			final var superState = getSuperclassInheritanceState( returnedClassOrElement, inheritanceStatePerClass );
+			if ( superState != null && superState.isEmbeddableSuperclass() ) {
+				superState.postProcess( component );
+			}
+		}
 
 		final XClass annotatedClass = inferredData.getPropertyClass();
 		final Map<String, String> subclassToSuperclass = component.isPolymorphic() ? new HashMap<>() : null;
@@ -510,19 +519,19 @@ private static void bindDiscriminator(
 			PropertyData propertyData,
 			InheritanceState inheritanceState,
 			MetadataBuildingContext context) {
-		if ( inheritanceState == null ) {
-			return;
-		}
-		final AnnotatedDiscriminatorColumn discriminatorColumn = processEmbeddableDiscriminatorProperties(
-				componentClass,
-				propertyData,
-				parentHolder,
-				holder,
-				inheritanceState,
-				context
-		);
-		if ( discriminatorColumn != null ) {
-			bindDiscriminatorColumnToComponent( component, discriminatorColumn, holder, context );
+		// Discriminated inheritance only applies to explicit @Embeddable types
+		if (  !inheritanceState.isEmbeddableSuperclass()) {
+			final AnnotatedDiscriminatorColumn discriminatorColumn = processEmbeddableDiscriminatorProperties(
+					componentClass,
+					propertyData,
+					parentHolder,
+					holder,
+					inheritanceState,
+					context
+			);
+			if ( discriminatorColumn != null ) {
+				bindDiscriminatorColumnToComponent( component, discriminatorColumn, holder, context );
+			}
 		}
 	}
 

hibernate-core/src/main/java/org/hibernate/boot/model/internal/InheritanceState.java

@@ -332,7 +332,9 @@ private org.hibernate.mapping.MappedSuperclass processMappedSuperclass(Table imp
 				superEntityState != null ?
 						buildingContext.getMetadataCollector().getEntityBinding( superEntityState.getClazz().getName() ) :
 						null;
-		final int lastMappedSuperclass = classesToProcessForMappedSuperclass.size() - 1;
+		final int lastMappedSuperclass = isEmbeddableSuperclass
+				? classesToProcessForMappedSuperclass.size()
+				: classesToProcessForMappedSuperclass.size() - 1;
 		org.hibernate.mapping.MappedSuperclass mappedSuperclass = null;
 		for ( int index = 0; index < lastMappedSuperclass; index++ ) {
 			org.hibernate.mapping.MappedSuperclass parentSuperclass = mappedSuperclass;