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Re: [netmod] Interaction of 'when' and 'default' statements

Martin Bjorklund <mbj@tail-f.com> Wed, 22 March 2017 18:23 UTC

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Date: Wed, 22 Mar 2017 19:23:00 +0100
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Subject: Re: [netmod] Interaction of 'when' and 'default' statements
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William Ivory <wivory@Brocade.com> wrote:
> Hi Martin,
> 
> Thanks.  Can you point me at the part of RFC 6020 that explicitly
> states that 'when' wins over 'default'?

Section 7.6.1 of RFC 7950 says:

   Note that if the leaf or any of its ancestors has a "when" condition
   or "if-feature" expression that evaluates to "false", then the
   default value is not in use.


/martin


> 
> William
> 
> -----Original Message-----
> From: Martin Bjorklund [mailto:mbj@tail-f.com] 
> Sent: 22 March 2017 17:53
> To: William Ivory <wivory@Brocade.com>
> Cc: netmod@ietf.org; Nick Brown <brownn@Brocade.com>
> Subject: Re: [netmod] Interaction of 'when' and 'default' statements
> 
> William Ivory <wivory@Brocade.com> wrote:
> > Hi,
> > 
> > I'm looking for clarification of the 'when' and 'default' statements 
> > on a leaf.  For example, if a leaf has a 'default', can it also have a 
> > 'when' statement that could cause it to disappear if the 'when'
> > condition evaluates to false?
> 
> Yes, and in that case the default doesn't apply.
> 
> > Section 8.3 or RFC 6020 isn't clear on how evaluation of constraints 
> > should be done here, and neither the section on the 'when' statement 
> > nor the 'default' section have any cross-references.
> 
> If the "when" expression evaluates to false, it's like if the whole node doesn't exist.  A client can't set it etc.
> 
> 
> /martin
>

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