Thx. In the case I'm most concerned about, a-list (and all descendants) is
config true and 'entry' is the key leaf. So all a-list entries have a node
called 'entry' by definition.
(I'm regretting using the name 'entry' for my key now in this example 😊
In this case it seems all the following result in the equivalent behavior
(checking that a-list has at least one entry):
must "../a-list";
must "../a-list[entry=*]";
must "../a-list[entry]"; <- this confuses me but I'll take your word
for it
must "../a-list/entry";
must "../a-list[entry=*]/entry";
must "../a-list[entry]/entry"; <- not sure about this one
Rgds,
Jason
> -----Original Message-----
> From: Martin Bjorklund [mailto:[email protected]]
> Sent: Wednesday, March 28, 2018 1:28 PM
> To: Sterne, Jason (Nokia - CA/Ottawa) <[email protected]>
> Cc: [email protected]; [email protected]
> Subject: Re: [netmod] YANG 'must' Xpaths, predicates and wildcards
>
> "Sterne, Jason (Nokia - CA/Ottawa)" <[email protected]> wrote:
> > Thanks Alex. Sorry about those sloppy mistakes. I agree about the
> > ../a-list and I should have said count > 0.
> >
> > In the 2nd part of my email, my intention was to only allow foo to be
> > configured if a-list has at least one entry configured. So I don't
> > think min-elements 1 would work. I don't want to always require an
> > entry in a-list. I only want to require one if foo is configured.
> >
> > I guess this also achieves the same thing right ?
> > must "../a-list[entry=*]";
>
> Yes, if all a-list entries has a node called "entry". But if that't
> what you want, do:
>
> must "../a-list[entry]";
>
>
> > If foo has a default value, then does that mean the "must" is
> > evaluated even if foo is deleted from the config ?
> > leaf foo {
> > must "../a-list"; <- always evaluated because of default ?
> > type uint16;
> > default 5;
> > }
> > If the must is always evaluated then it would be the equivalent of
> > having min-elements 1 in a-list.
>
>
> Correct.
>
>
> /martin
>
> >
> > Rgds,
> > Jason
> >
> > From: Alex Campbell [mailto:[email protected]]
> > Sent: Tuesday, March 27, 2018 9:57 PM
> > To: Sterne, Jason (Nokia - CA/Ottawa) <[email protected]>;
> > [email protected]
> > Subject: Re: YANG 'must' Xpaths, predicates and wildcards
> >
> >
> > Hi,
> >
> >
> >
> > For one thing, it should be ../a-list since a-list is not a child of
> > foo.
> >
> > Also - if foo is not configured and has no default value, then any
> > must expressions in foo are not evaluated because it is not part of
> > the "accessible tree". (I tested this in ConfD)
> >
> > Apart from these issues, yes it will behave as you expect - it will
> > fail if a-list contains no entries.
> >
> >
> >
> > must "count(a-list) > 1"; is not equivalent since it requires at least
> > two entries.
> >
> >
> >
> > However, you can more simply add a min-elements 1; statement to a-list
> > to achieve the same goal - no XPath required.
> >
> >
> >
> > ________________________________
> > From: netmod <[email protected]<mailto:netmod-
> [email protected]>>
> > on behalf of Sterne, Jason (Nokia - CA/Ottawa)
> > <[email protected]<mailto:[email protected]>>
> > Sent: Wednesday, 28 March 2018 1:10 p.m.
> > To: [email protected]<mailto:[email protected]>
> > Subject: [netmod] YANG 'must' Xpaths, predicates and wildcards
> >
> > Hi all,
> >
> > I'm pretty sure that this xpath (e.g. in a must statement) isn't
> > correct:
> >
> > (A) ../container-a/list-b[name=*]/some-leaf
> >
> > and should just be this instead:
> >
> > (B) ../container-a/list-b/some-leaf
> >
> > Or is the * an allowable wildcard for a key value in a predicate ?
> >
> > I also had a question about whether the following "must" correctly
> > checks that at least one entry exists in a-list.
> >
> > container c1 {
> > leaf foo {
> > must "a-list";
> > type uint16;
> > }
> > list a-list {
> > key "entry";
> > leaf entry {
> > type uint16;
> > }
> > leaf another-entry {
> > type uint32;
> > }
> > }
> > }
> >
> > I think I could also replace that must with the following:
> > must "count(a-list) > 1";
> > but does must "a-list"; achieve the same thing ?
> >
> > Rgds,
> > Jason
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