lyd_diff_apply_all fails on replace operation for non-existing leaf (RFC compliance question)

[vilkovalexander]

Hello, and thank you for your work on libyang!

According to RFC 7950, section 7.6.7, the replace operation is intended to behave as a combination of delete and create. In the context of a operation, this implies that if a leaf does not exist and is targeted with replace, it should be created.

However, when using lyd_diff_apply_all() with a diff that includes a replace operation on a non-existent leaf, the function returns an error instead of creating the leaf node.

Example:

leaf foo {
  type string;
}

If the current data tree does not contain foo, and the diff contains a replace operation like foo = "bar", the operation fails rather than creating the foo node with the new value.

Question: Is this the intended behavior in libyang, or is this a deviation from RFC 7950?

Thank you in advance for your clarification!

[michalvasko]

Be careful, libyang defines functions for diff, which is something else than edit. The latter should fully conform to edit-config operations and is used in sysrepo/netopeer2. diff is a proprietary format representing "resolved edit" meaning every create operation must actually create data, every remove remove them, and every replace replace them.