Index inherited compound identity restoration

internal/engine/inheritance_scope.go

@@ -144,18 +144,24 @@ func preserveInheritanceIdentityFields(merged, child *document.Node, fields []st
 	if len(fields) == 0 || merged == nil || merged.Kind != document.Mapping || child == nil || child.Kind != document.Mapping {
 		return
 	}
+	identityFields := make(map[string]struct{}, len(fields))
 	for _, field := range fields {
-		for _, entry := range child.Mapping {
-			if entry.Key != field {
-				continue
-			}
-			for index := range merged.Mapping {
-				if merged.Mapping[index].Key == field {
-					merged.Mapping[index] = document.Entry{Key: field, Value: document.Clone(entry.Value)}
-					break
-				}
-			}
-			break
+		identityFields[field] = struct{}{}
+	}
+	positions := make(map[string]int, len(merged.Mapping))
+	for index, entry := range merged.Mapping {
+		if _, exists := positions[entry.Key]; !exists {
+			positions[entry.Key] = index
+		}
+	}
+	for _, entry := range child.Mapping {
+		if _, identity := identityFields[entry.Key]; !identity {
+			continue
+		}
+		delete(identityFields, entry.Key)
+		if index, exists := positions[entry.Key]; exists {
+			entry.Value = document.Clone(entry.Value)
+			merged.Mapping[index] = entry
 		}
 	}
 }