HHH-13815 TransientObjectException after merging a bidirectional one-to-many with orphan deletion

Author: dreab8

hibernate-core/src/main/java/org/hibernate/collection/spi/AbstractPersistentCollection.java

@@ -1297,8 +1297,8 @@ protected static <E> Collection<E> getOrphans(
 		// iterate over the *old* list
 		for ( E old : oldElements ) {
 			if ( !currentSaving.contains( old ) ) {
-				final Object oldId = ForeignKeys.getEntityIdentifierIfNotUnsaved( entityName, old, session );
-				if ( !currentIds.contains( useIdDirect ? oldId : new TypedValue( idType, oldId ) ) ) {
+				final Object oldId = ForeignKeys.getEntityIdentifier( entityName, old, session );
+				if ( oldId != null && !currentIds.contains( useIdDirect ? oldId : new TypedValue( idType, oldId ) ) ) {
 					res.add( old );
 				}
 			}

hibernate-core/src/main/java/org/hibernate/engine/internal/ForeignKeys.java

@@ -371,6 +371,21 @@ public static Object getEntityIdentifierIfNotUnsaved(
 		}
 	}
 
+	public static Object getEntityIdentifier(
+			final String entityName,
+			final Object object,
+			final SharedSessionContractImplementor session) {
+		if ( object == null ) {
+			return null;
+		}
+		else {
+			final Object id = session.getContextEntityIdentifier( object );
+			return id == null
+					? session.getEntityPersister( entityName, object ).getIdentifier( object, session )
+					: id;
+		}
+	}
+
 	private static void throwIfTransient(String entityName, Object object, SharedSessionContractImplementor session) {
 		if ( isTransient( entityName, object, Boolean.FALSE, session ) ) {
 			throw new TransientObjectException(