Re: [netmod] Adding a pre-existing leaf into a new 'choice' - NBC change?

[Martin Bjorklund <[e-mail]>]

Hi,

"Sterne, Jason (Nokia - CA/Ottawa)" <[e-mail]> wrote:
> Hi all,
> 
> If we have a YANG model with a leaf:
> 
> MODEL VERSION 1:
> container my-model {
>     leaf a { type string; }
> }
> 
> And then later we produce another version of the model where that leaf
> is placed into a choice construct:
> 
> MODEL VERSION 2:
> container my-model {
>     choice some-choice {
>         case x {
>             leaf a { type string; }
>         }
>     }
> }
> 
> Is that considered a non-backwards-compatible change?

Not accordning to current RFC 7950 rules, since it changes the schema
node path (suppose the leaf was a container, and someone had augment
/my-model/a).

> Does the answer depend on whether the choice contains other cases (or
> other cases that are the default case)?

No.

> MODEL VERSION 3:
> container my-model {
>     choice some-choice {
>         case x {
>             leaf a { type string; }
>         }
>         case y {
>             leaf b { type string; }
>         }
>     }
> }
> 
> A client 'foo' using VERSION 1 would still be able to set & read back
> leaf a in the same way as it always did.
> 
> But if another client 'bar' (using VERSION 3) sets leaf 'b', then leaf
> 'a' would disappear. That could be surprising to client 'foo' although
> perhaps no more surprising than if another client simply deletes leaf
> 'a' (using VERSION 1).



/martin