Re: [netmod] Whitespace in XML encoding - allowed ?

Balázs Lengyel <balazs.lengyel@ericsson.com> Fri, 12 October 2018 14:13 UTC

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Thread-Topic: [netmod] Whitespace in XML encoding - allowed ?
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Subject: Re: [netmod] Whitespace in XML encoding - allowed ?
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Hello,

Thanks for all the replies. So preceding and following whitespace is not allowed.
However as I got similar questions often, and some RFC examples seem to indicate that it is allowed, I feel that an explanatory statement like the following would help YANG users.:

"It is not allowed to add preceding or following whitespace after the value of a leaf/leaf-list.
Note that some text documents may add whitespace to Netconf examples to avoid long lines,
however this extra whitespace MUST NOT be present in the actual Netconf encoding."

regards Balazs

On 2018. 10. 09. 10:59, Balázs Lengyel wrote:

Hello,

Recently we came up against a problem where a certain implementation did not accept the following:

<with-defaults xmlns="...">
    report-all
</with-defaults>

while it did accept

<with-defaults xmlns="...">report-all</with-defaults>

I am unsure whether YANG's XML encoding allows whitespace before and after a leaf's value? In RFC7950 it does not say yes or no. I have found the following examples that seem to allow preceding/following whitespace:

https://tools.ietf.org/html/rfc7950#section-4.2.9" rel="nofollow">https://tools.ietf.org/html/rfc7950#section-4.2.9

       <status xmlns=http://example.com/system" rel="nofollow">"http://example.com/system">
         The image example-fw-2.3 is being installed.
       </status>

https://tools.ietf.org/html/rfc7950#section-7.16.3" rel="nofollow">https://tools.ietf.org/html/rfc7950#section-7.16.3

         <reporting-entity>
           /ex:interface[ex:name='Ethernet0']
         </reporting-entity>

https://tools.ietf.org/html/rfc6243#appendix-A.3.1" rel="nofollow">https://tools.ietf.org/html/rfc6243#appendix-A.3.1

        <with-defaults
         xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults">
          report-all
        </with-defaults>

It is problematic that this is not clarified. IMHO this should be clarified in an errata to rfc7950. Chose one:

  1. It is not allowed to add preceding or following whitespace after the value of a leaf/leaf-list.
    Note that some text documents may add whitespace to Netconf examples to avoid long lines,
    however this extra whitespace MUST NOT be present in the actual Netconf encoding.
  2. It is not allowed to add preceding or following whitespace after the value of a leaf/leaf-list.
  3. It is allowed to add preceding or following whitespace after the value of a leaf/leaf-list except
    for string based types, where the whitespace could be part of the leaf's value itself..

What do you think?

regards Balazs

-- 
Balazs Lengyel                       Ericsson Hungary Ltd.
Senior Specialist
Mobile: +36-70-330-7909              email: Balazs.Lengyel@ericsson.com 

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-- 
Balazs Lengyel                       Ericsson Hungary Ltd.
Senior Specialist
Mobile: +36-70-330-7909              email: Balazs.Lengyel@ericsson.com