Re: [yang-doctors] Fwd: Re: Issue with [e-mail] and yangdump-pro

[Ladislav Lhotka <[e-mail]>]

Michal Vaško <[e-mail]> writes:

> Hello everyone,
>
> we would like to clarify a few things from this discussion. We are
> displaying some warnings in case of some almost-certainly invalid
> XPath expressions so we were wondering if it makes sense to add
> another if we detect an equality comparison of an identityref and an
> identity name without the use of derived-from(-or-self)() functions.

Certainly for YANG 1.1 modules.

>
> Another issue, "local module" has no formal definition as was
> mentioned. One can infer it is the module where the statement in
> question is defined but a definition would be appreciated. The same
> problem is with the term "current module" which it seems can be used
> interchangeably. Lastly, "current node" has no definition either and
> so we assumed it to be the node returned by the function current().

As I already proposed, it would be better to declare the result of such
comparisons as undefined.

Lada

>
> Kind regards,
> Michal
>
> On Monday, December 25, 2017 20:14 CET, Andy Bierman <[e-mail]> wrote: 
>  
>> On Mon, Dec 25, 2017 at 10:53 AM, Ladislav Lhotka <[e-mail]> wrote:
>> 
>> > On Sun, 2017-12-24 at 18:54 -0300, Mahesh Jethanandani wrote:
>> > > > On Dec 23, 2017, at 10:49 AM, Martin Bjorklund <[e-mail]> wrote:
>> > > >
>> > > > Ladislav Lhotka <[e-mail]> wrote:
>> > > > > > On Sat, 2017-12-23 at 13:01 +0100, Martin Bjorklund wrote:
>> > > > > > Andy Bierman <[e-mail]> wrote:
>> > > > > > > > On Sat, Dec 23, 2017 at 2:21 AM, Martin Bjorklund <
>> > [e-mail]>
>> > > > > > > > wrote:
>> > > > > > > >
>> > > > > > > > Hi,
>> > > > > > > >
>> > > > > > > > See section 9.10.3 in RFC 7950:
>> > > > > > > >
>> > > > > > > >   The string value of a node of type "identityref" in a "must"
>> > or
>> > > > > > > >   "when" XPath expression is the referred identity's qualified
>> > name
>> > > > > > > >   with the prefix present.
>> > > > > > > >
>> > > > > > > > and re. the prefix:
>> > > > > > > >
>> > > > > > > >   If the referred identity is defined in an
>> > > > > > > >   imported module, the prefix in the string value is the prefix
>> > > > > > > > defined
>> > > > > > > >   in the corresponding "import" statement.  Otherwise, the
>> > prefix in
>> > > > > > > >   the string value is the prefix for the current module.
>> > > > > > > >
>> > > > > > > >
>> > > > > > > > I most cases you should consider using derived-from-or-self
>> > instead
>> > > > > > > > of
>> > > > > > > > equality test for identiyrefs.
>> > > > > > >
>> > > > > > > So what is "the current module"?
>> > > > > > > What is the resolution of 'X'? Is it foo:X or bar:X?
>> > > > > >
>> > > > > > foo:X
>> > > > >
>> > > > > No, the resolution of 'X' is 'X'
>> > > >
>> > > > Yes!  Sorry, I misread the question.  I though the question was what
>> > > > prefix should be used.
>> > >
>> > > The question started with a 'when' statement (which I understand should
>> > be
>> > > changed to 'derived-from') using a identity name that is defined in the
>> > other
>> > > (bar) module. Should the 'derived-from' statement reference the identity
>> > using
>> > > the prefix 'b:X' or just 'X', using Andy's example?
>> >
>> > Both are possible in Andy's example, the former refers to the identity "X"
>> > defined in module "bar", the latter refers to the identity "X" defined in
>> > the
>> > local module ("foo").
>> >
>> >
>> I see the term "local module" used 11 times in RFC 7950, but it is not
>> defined anywhere.
>> IMO the only intuitive solution is that all scoped names are resolved in
>> the same module,
>> which is the module defining the actual statements. Is that the local
>> module?
>> 
>> 
>> Lada
>> >
>> 
>> 
>> Andy
>> 
>> 
>> >
>> > >
>> > > >
>> > > >
>> > > > /martin
>> > > >
>> > > >
>> > > > > because it is an XPath 1.0 string and XPath
>> > > > > knows nothing about YANG identities. Because of the rule of sec.
>> > 9.10.3,
>> > > > > the
>> > > > > equality expression is always false.
>> > > > >
>> > > > > That's why we introduced the new XPath functions derived-from() and
>> > > > > derived-
>> > > > > from-or-self() in YANG 1.1.
>> > > > >
>> > > > > Lada
>> > > > >
>> > > > > >
>> > > > > >
>> > > > > > /martin
>> > > > > >
>> > > > > >
>> > > > > > >
>> > > > > > >
>> > > > > > >
>> > > > > > > >
>> > > > > > > > /martin
>> > > > > > >
>> > > > > > > Andy
>> > > > > > >
>> > > > > > >
>> > > > > > > >
>> > > > > > > >
>> > > > > > > >
>> > > > > > > > Andy Bierman <[e-mail]> wrote:
>> > > > > > > > > > On Fri, Dec 15, 2017 at 4:38 AM, Radek Krejčí <
>> > [e-mail]
>> > > > > > > > > > > wrote:
>> > > > > > > > > >
>> > > > > > > > > > Hi,
>> > > > > > > > > > I'm adding Michal Vasko to cc, he knows better how these
>> > things
>> > > > > > > > > > are
>> > > > > > > > > > checked in libyang.
>> > > > > > > > > >
>> > > > > > > > > > It seems to me that Andy refers the text which does not
>> > apply
>> > > > > > > > > > here.
>> > > > > > > > > > The
>> > > > > > > > > > identity name was used as part of XPath expresion
>> > (when-stmt),
>> > > > > > > > > > so the
>> > > > > > > > > > definition of the context nodes for the when-stmt (RFC
>> > 7950, sec
>> > > > > > > >
>> > > > > > > > 7.21.5)
>> > > > > > > > > > and XPath context rules should apply here. Not the rules
>> > for the
>> > > > > > > > > > identityref's base statement. In this case, the when-stmt
>> > is in
>> > > > > > > >
>> > > > > > > > augment so
>> > > > > > > > > > the context node (which we also understand as the current
>> > node
>> > > > > > > > > > in this
>> > > > > > > > > > case) is the augment's target node. And according to XPath
>> > > > > > > > > > context
>> > > > > > > >
>> > > > > > > > rules
>> > > > > > > > > > (RFC 7950, sec 6.4.1):
>> > > > > > > > > >
>> > > > > > > > > > o  Names without a namespace prefix belong to the same
>> > namespace
>> > > > > > > > > > as
>> > > > > > > >
>> > > > > > > > the
>> > > > > > > > > > identifier of the current node.
>> > > > > > > > >
>> > > > > > > > >
>> > > > > > > > > I cc:ed YANG doctors to get more opinions...
>> > > > > > > > >
>> > > > > > > > > The current node is the augment-stmt.
>> > > > > > > > > Note that it does not say context node, which is the target
>> > of the
>> > > > > > > >
>> > > > > > > > augment.
>> > > > > > > > > I think prefixes (and default prefix) are resolved in the
>> > module
>> > > > > > > >
>> > > > > > > > containing
>> > > > > > > > > the statement.
>> > > > > > > > >
>> > > > > > > > >
>> > > > > > > > > module foo {
>> > > > > > > > >
>> > > > > > > > >   import bar { prefix b; }
>> > > > > > > > >   identity X;
>> > > > > > > > >
>> > > > > > > > >   augment b:/some-node {
>> > > > > > > > >      leaf test {
>> > > > > > > > >         type string;
>> > > > > > > > >         when "/b:some-node/b:other-node = 'X'";
>> > > > > > > > >      }
>> > > > > > > > >   }
>> > > > > > > > > }
>> > > > > > > > >
>> > > > > > > > > module bar {
>> > > > > > > > >
>> > > > > > > > >   identity W;
>> > > > > > > > >   identity X { base W; }
>> > > > > > > > >   container some-node {
>> > > > > > > > >       leaf other-node {
>> > > > > > > > >         type identityref { base W; }
>> > > > > > > > >       }
>> > > > > > > > >   }
>> > > > > > > > > }
>> > > > > > > > >
>> > > > > > > > > Q) Does other-node = 'X' resolve to foo:X or bar:X?  IMO:
>> > foo:X
>> > > > > > > > >
>> > > > > > > > >
>> > > > > > > > >
>> > > > > > > > > Andy
>> > > > > > > > >
>> > > > > > > > >
>> > > > > > > > >
>> > > > > > > > > > In this particular case, the augment node with the
>> > when-stmt
>> > > > > > > > > > augments
>> > > > > > > >
>> > > > > > > > the
>> > > > > > > > > > same module which defines napt44, so they are in the
>> > correct
>> > > > > > > > > > namespace
>> > > > > > > >
>> > > > > > > > and
>> > > > > > > > > > the identity name can be used without the prefix. So it
>> > should
>> > > > > > > > > > be
>> > > > > > > > > > fine,
>> > > > > > > > > > while I believe that using prefix in the cases of
>> > identities is
>> > > > > > > > > > always
>> > > > > > > > > > better approach. From the first sight (it may be
>> > challenging for
>> > > > > > > > > > human
>> > > > > > > >
>> > > > > > > > to
>> > > > > > > > > > correctly resolve the context/current node in some cases),
>> > I
>> > > > > > > > > > would
>> > > > > > > > > > also
>> > > > > > > > > > expect prefix.
>> > > > > > > > > >
>> > > > > > > > > > I propose to keep the change in the draft (added nat
>> > prefix),
>> > > > > > > > > > since it
>> > > > > > > > > > improves readability of the expression. But I don't think
>> > that
>> > > > > > > > > > it is
>> > > > > > > > > > an
>> > > > > > > > > > error to ommit the prefix.
>> > > > > > > > > >
>> > > > > > > > > > Regards,
>> > > > > > > > > > Radek
>> > > > > > > > > >
>> > > > > > > > > >
>> > > > > > > > > > Dne 19.11.2017 v 20:42 Benoit Claise napsal(a):
>> > > > > > > > > > > Hi Radek,
>> > > > > > > > > > >
>> > > > > > > > > > > Here is a bug report for you.
>> > > > > > > > > > >
>> > > > > > > > > > > Regards, Benoit
>> > > > > > > > > > >
>> > > > > > > > > > >
>> > > > > > > > > > > -------- Forwarded Message --------
>> > > > > > > > > > > Subject:      Re: Issue with [e-mail]
>> > and
>> > > > > > > > > >
>> > > > > > > > > > yangdump-pro
>> > > > > > > > > > > Date:         Sat, 18 Nov 2017 13:22:58 -0800
>> > > > > > > > > > > From:         Andy Bierman <[e-mail]>
>> > > > > > > > > > > To:   Benoit Claise <[e-mail]>
>> > > > > > > > > > > CC:   [e-mail] <
>> > > > > > > > > >
>> > > > > > > > > > [e-mail]>, Mahesh
>> > Jethanandani <
>> > > > > > > > > > [e-mail]>
>> > > > > > > > > > >
>> > > > > > > > > > >
>> > > > > > > > > > >
>> > > > > > > > > > > Hi,
>> > > > > > > > > > >
>> > > > > > > > > > > yangdump-pro is correct. Every other compiler missed
>> > it...
>> > > > > > > > > > >
>> > > > > > > > > > > 9.10.2.  The identityref's "base" Statement
>> > > > > > > > > > >
>> > > > > > > > > > >   The "base" statement, which is a substatement to the
>> > "type"
>> > > > > > > > > > >   statement, MUST be present at least once if the type is
>> > > > > > > > > > >   "identityref".  The argument is the name of an
>> > identity, as
>> > > > > > > >
>> > > > > > > > defined
>> > > > > > > > > > >   by an "identity" statement.  If a prefix is present on
>> > the
>> > > > > > > >
>> > > > > > > > identity
>> > > > > > > > > > >   name, it refers to an identity defined in the module
>> > that
>> > > > > > > > > > > was
>> > > > > > > > > > >   imported with that prefix.  *Otherwise, an identity
>> > with the
>> > > > > > > >
>> > > > > > > > matching
>> > > > > > > > > > name MUST be defined in the current module or an included
>> > > > > > > > > > submodule.*
>> > > > > > > > > > >
>> > > > > > > > > > > Using [e-mail] and
>> > [e-mail]
>> > > > > > > > > > >
>> > > > > > > > > > > When I change 'natp44' to 'nat:natp44' in both
>> > when-stmts:
>> > > > > > > > > > >
>> > > > > > > > > > > andy@andy-homedev:~/Desktop/FD1289/IETF$ yangdump-pro
>> > > > > > > > > >
>> > > > > > > > > > [e-mail] modpath=.
>> > > > > > > > > > >
>> > > > > > > > > > > *** /home/andy/Desktop/FD1289/
>> > IETF/[e-mail]
>> > > > > > > > > > > *** 0 Errors, 0 Warnings
>> > > > > > > > > > >
>> > > > > > > > > > > andy@andy-homedev:~/Desktop/FD1289/IETF$
>> > > > > > > > > > >
>> > > > > > > > > > >
>> > > > > > > > > > > Andy
>> > > > > > > > > > >
>> > > > > > > > > > >
>> > > > > > > > > > > On Sat, Nov 18, 2017 at 11:07 AM, Benoit Claise
>> > <bclaise@cisco
>> > > > > > > > > > > .com
>> > > > > > > > > >
>> > > > > > > > > > <mailto:[e-mail]>> wrote:
>> > > > > > > > > > >
>> > > > > > > > > > >    Hi Andy,
>> > > > > > > > > > >
>> > > > > > > > > > >    Can you please have a look at
>> > [e-mail]
>> > > > > > > > > > > at
>> > > > > > > > > >
>> > > > > > > > > > http://www.claise.be/IETFYANGPageCompilation.html <
>> > > > > > > >
>> > > > > > > > http://www.claise.be/
>> > > > > > > > > > IETFYANGPageCompilation.html> .
>> > > > > > > > > > >    yangdump-pro reports a new error, while the other
>> > > > > > > > > > > validators are
>> > > > > > > > > >
>> > > > > > > > > > fine.
>> > > > > > > > > > >
>> > > > > > > > > > >    Copying Mahesh, as YANG doctor.
>> > > > > > > > > > >
>> > > > > > > > > > >    Regards, Benoit
>> > > > > >
>> > > > > > _______________________________________________
>> > > > > > yang-doctors mailing list
>> > > > > > [e-mail]
>> > > > > > https://www.ietf.org/mailman/listinfo/yang-doctors
>> > > > >
>> > > > > --
>> > > > > Ladislav Lhotka
>> > > > > Head, CZ.NIC Labs
>> > > > > PGP Key ID: 0xB8F92B08A9F76C67
>> > > >
>> > > > _______________________________________________
>> > > > yang-doctors mailing list
>> > > > [e-mail]
>> > > > https://www.ietf.org/mailman/listinfo/yang-doctors
>> > --
>> > Ladislav Lhotka
>> > Head, CZ.NIC Labs
>> > PGP Key ID: 0xB8F92B08A9F76C67
>> >
>> > _______________________________________________
>> > yang-doctors mailing list
>> > [e-mail]
>> > https://www.ietf.org/mailman/listinfo/yang-doctors
>> >
>  
>  
>

-- 
Ladislav Lhotka
Head, CZ.NIC Labs
PGP Key ID: 0xB8F92B08A9F76C67