Hi,I would just like to include the text that I think restricts this use of the augment-structure. It is in the description of this extension in RFC 8791 <https://datatracker.ietf.org/doc/html/rfc8791>.
The mandatory 'path' parameter value identifies the YANG conceptual data node that is being augmented and is represented as an absolute-schema-nodeid string, where the first node in the absolute-schema-nodeid string identifies the YANG data structure to augment, and the rest of the nodes in the string identifies the node within the YANG structure to augment.It clearly mentions referencing a "conceptual data node", not a 'structure' extension. I think this is the reason we have not supported it in 'libyang'. Note that I do not mind adding support for this in libyang (we have already implemented it) but the wording is definitely misleading if the intention was for 'structure' to be allowed to be augmented directly. Maybe even deserves an errata.
Regards, Michal On 2. 10. 2025 8:38, Phú Liên wrote:
---------- Forwarded message --------- From: *Phú Liên* <[email protected]> Date: Thu, Oct 2, 2025 at 1:36 PMSubject: Re: [netmod] Question about using augment-structure to augment the root node of a Yang data structureTo: Andy Bierman <[email protected]> Hi Andy, Thank you for your confirmation. I can now request a bug fix for Yanglint. Best regards, Phu On Thu, Oct 2, 2025 at 12:02 AM Andy Bierman <[email protected]> wrote: On Wed, Oct 1, 2025 at 12:56 AM Phú Liên <[email protected]> wrote: Hi RFC 8791 authors, I have a question regarding YANG data structure extensions (RFC 8791) and the use of augment-structure. Specifically, is it possible to augment the root of a YANG data structure? For example, with the YANG model below, yanglint validates successfully if the last "sx:augment-structure /foo:mystruct" statement is commented out. However, if that statement is included, yanglint reports an error: * Yang model ``` module foo { namespace "foo"; prefix foo; import ietf-yang-structure-ext { prefix sx; } sx:structure mystruct { container mycontainer { leaf leaf1 { type string; } } } sx:augment-structure /foo:mystruct/foo:mycontainer { leaf leaf2 { type string; } } // Augment to the root of the structure, so `leaf3` will be a sibling of `mycontainer`. sx:augment-structure /foo:mystruct { leaf leaf3 { type string; } } } ``` * Yanglint error ``` libyang err : Augment extension target node "/foo:mystruct" from module "foo" was not found. (/foo:{extension='sx:augment-structure'}/{augment='/foo:mystruct'}) ``` Moreover, if we cannot use augment-structure to add augments to the root of a structure, could you please suggest how to make the following leafref path valid in the YANG model below? I do not see any text in RFC 8791 that prohibits augmenting the structure. A valid path argument is provided to the extension. sx:augment-structure /foo:mystruct The structure 'mystruct' should be treated like a top-level NP container. It shares the same namespace as real data-def-stmts. Andy * a.yang ``` module a { namespace "urn:a"; prefix a; import b { prefix b; } import ietf-yang-structure-ext { prefix sx; } grouping leafrefs { leaf leaf1 { type leafref { path "/a:top/a:leaf2"; } } } grouping leaves { leaf leaf2 { type string; } } container top { config false; uses leaves; } // Augments 'a:leaf1' into '/b:mystruct/b:mycontainer'. This augmented // 'a:leaf1' will be a sibling of 'b:myleaf'. // // XPath within a structure can only reference nodes inside the same // structure. Therefore, '/a:top/a:leaf2' must also be augmented into // 'b:mystruct' to satisfy the leafref path. sx:augment-structure "/b:mystruct/b:mycontainer" { uses leafrefs; } // This 'augment-structure' attempts to satisfy the leafref path by augmenting // '/a:top/a:leaf2' into the root of '/b:mystruct'. However, yanglint reports // an error because we are augmenting to the root of a structure. sx:augment-structure "/b:mystruct" { container top { uses leaves; } } // This 'augment-structure' is valid in yanglint but does not satisfy the // leafref path because it augments '/b:top/a:leaf2', not '/a:top/a:leaf2'. sx:augment-structure "/b:mystruct/b:top" { uses leaves; } } ``` * b.yang ``` module b { namespace "urn:b"; prefix b; import ietf-yang-structure-ext { prefix sx; } sx:structure mystruct { container mycontainer { leaf myleaf { type string; } } container top { } } } ``` Yanglint reports the following error for the second augment-structure statement: ``` libyang err : Augment extension target node "/b:mystruct" from module "a" was not found. (/a:{extension='sx:augment-structure'}/{augment='/b:mystruct'}) ``` And the following error for the third augment-structure statement: ``` libyang err : Not found node "top" in path. (/b:mycontainer/a:leaf1) ``` By the way, we found that this use of augment-structure is claimed to be supported in the following links: * https://docs.yumaworks.com/en/latest/yangauto/define-abstract-yang.html * https://dr2lopez.github.io/yang-provenance/draft-lopez-opsawg-yang-provenance.html BR/Phu _______________________________________________ netmod mailing list -- [email protected] To unsubscribe send an email to [email protected] _______________________________________________ netmod mailing list [email protected] To unsubscribe send an email [email protected]
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