For those procedures that return either post_op_attr or wcc_data structures on failure, the discriminated union may contain the pre-operation attributes of the object or object parent directory. This depends on the error encountered and may also depend on the particular server implementation. Implementors are strongly encouraged to return as much attribute data as possible upon failure, but client implementors need to be aware that their implementation must correctly handle the variant return instance where no attributes or consistency data is returned.