JOEY BOYD <[email protected]> wrote:
> Hello,
>
> Does anyone have thoughts on this?
>
> Regards,
> Joey
>
> -----Original Message-----
> From: JOEY BOYD
> Sent: Wednesday, September 27, 2017 9:06 AM
> To: '[email protected]'
> Subject: Backward Compatibility Question
>
> Hi all,
>
> Suppose I had a published YANG model with the following leaf.
>
>
> leaf thing1 {
> type uint8;
> description
> "Thing 1.";
> }
>
> Later, I realize that I wish I had modeled this in a choice as I now have a
> mutually exclusive option to 'thing1' which I want to add to the model.
>
> leaf thing2 {
> type empty;
> description
> "Thing 2.";
> }
>
> This is a very simplified example but should be sufficient to demonstrate the
> problem.
>
> If I look at the XML representation of 'thing1', it looks like this.
>
> <thing1>123</thing1>
>
> If I were to move 'thing1' into a choice with a single case, it would look
> like this.
>
> choice things {
> case thing1 {
> leaf thing1 {
> type uint8;
> description
> "Thing 1.";
> }
> }
> }
>
> Looking to the XML representation, it looks the same as before.
But it is not backwards compatible, since the schema tree has
changed. Suppose that "thing1" was a container; then some other
module might have augmented that container. If you put the node in a
choice and case, the augment will no longer work.
/martin
>
> <thing1>123</thing1>
>
> To me, this means that taking a single node or set of nodes and moving them
> under a case within a new choice statement is a backward compatible change.
> This assumes, of course, any mandatory or default behavior is preserved. I
> now can add 'thing2' to the existing model as an option to 'thing1'.
>
> choice things {
> case thing1 {
> leaf thing1 {
> type uint8;
> description
> "Thing 1.";
> }
> }
> case thing2 {
> leaf thing2 {
> type empty;
> description
> "Thing 2.";
> }
> }
> }
>
> Do you agree with this analysis or am I missing something?
>
> Best regards,
> Joey
>
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