Re: [netmod] ?==?utf-8?q? mandatory choice with non-presence container case

Michal Vaško <mvasko@cesnet.cz> Mon, 24 June 2019 17:01 UTC

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From: =?utf-8?q?Michal_Va=C5=A1ko?= <mvasko@cesnet.cz>
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Date: Mon, 24 Jun 2019 19:01:29 +0200
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To: =?utf-8?q?Rob_Wilton_=28rwilton=29?= <rwilton@cisco.com>
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Subject: Re: [netmod] =?utf-8?b?Pz09P3V0Zi04P3E/ICBtYW5kYXRvcnkgY2hvaWNlIHdp?= =?utf-8?q?th_non-presence_container_case?=
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Hi Rob,
I think there is a problem in the RFC because using only allowed steps I got invalid data from initially valid data. That cannot be correct.

Regards,
Michal

On Monday, June 24, 2019 18:52 CEST, "Rob Wilton (rwilton)" <rwilton@cisco.com> wrote: 
 
> Hi Michal,
> 
> My thoughts:
> 
> According to 7.5.1:
> 
>    In the first style, the container has no meaning of its own, existing
>    only to contain child nodes.  In particular, the presence of the
>    container node with no child nodes is semantically equivalent to the
>    absence of the container node.  YANG calls this style a "non-presence
>    container".  This is the default style.
> 
> Hence your request (because the NP container does not have any children) is equivalent to:
> 
>  <TOP>
>    <L/>
>  </TOP>
> 
> which fails the "mandatory" check.
> 
> Thanks,
> Rob
> 
> 
> > -----Original Message-----
> > From: netmod <netmod-bounces@ietf.org> On Behalf Of Michal Vaško
> > Sent: 24 June 2019 17:39
> > To: netmod <netmod@ietf.org>
> > Subject: [netmod] mandatory choice with non-presence container case
> > 
> > Hi,
> > I have encountered a situation that I think is not covered by RFC 7950. My
> > specific use-case was as follows.
> > 
> > model:
> > 
> > container TOP {
> >   leaf L {
> >     type empty;
> >   }
> >   choice A {
> >     mandatory true;
> >     container C;
> >   }
> > }
> > 
> > data:
> > 
> > <TOP>
> >   <L/>
> >   <C/>
> > </TOP>
> > 
> > Parsing was successful, but printing these data back to XML produced:
> > 
> > <TOP>
> >   <L/>
> > </TOP>
> > 
> > and parsing this correctly failed with missing mandatory choice. According
> > to section 7.5.7 [1], I think the C container could be omitted but the
> > whole situation does not seem correct. Thank you for any input.
> > 
> > Regards,
> > Michal
> > 
> > [1] https://tools.ietf.org/html/rfc7950#section-7.5.7
> > 
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