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

[Andy Bierman <[e-mail]>]

On Mon, Nov 19, 2018 at 12:32 PM 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?
>


yes -- even though the data node /my-model/x did not change,
the schema node /my-model/a changed to /my-model/some-choice/x/a.
Any leafref path pointing at this leaf will break.


Andy


>
> 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).
>
>
>
> Jason
>
>
>
>
>
>
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