private ConfigOverlay applyUnsetUserProp(CommandOperation op, ConfigOverlay overlay) { List<String> name = op.getStrs(CommandOperation.ROOT_OBJ); if (op.hasError()) return overlay; for (String o : name) { if (!overlay.getUserProps().containsKey(o)) { op.addError(format("No such property ''{0}''", name)); } else { overlay = overlay.unsetUserProperty(o); } } return overlay; }