Thanks. I forgot that the choice is in the *schema* path (was thinking about
the instance data path which doesn't include the choice or case statements).
> -----Original Message-----
> From: Martin Bjorklund <m...@tail-f.com>
> Sent: Monday, November 19, 2018 3:46 PM
> To: Sterne, Jason (Nokia - CA/Ottawa) <jason.ste...@nokia.com>
> Cc: netmod@ietf.org
> Subject: Re: [netmod] Adding a pre-existing leaf into a new 'choice' - NBC
> change?
>
> Hi,
>
> "Sterne, Jason (Nokia - CA/Ottawa)" <jason.ste...@nokia.com> 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
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