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

[Mahesh Jethanandani <[e-mail]>]

> 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?

> 
> 
> /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 <[e-mail]
>>>>>>> 
>>>>>>> <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
>>> 
>>> _______________________________________________
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>>> https://www.ietf.org/mailman/listinfo/yang-doctors
>> -- 
>> Ladislav Lhotka
>> Head, CZ.NIC Labs
>> PGP Key ID: 0xB8F92B08A9F76C67
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