Also support RFC 8525, YANG Library, revision 2019-01-04

[kwatsen]

Description

Yangson currently supports the original RFC 7895, YANG Library, revision 2016-06-21.

This can be seen by grep-ing for the string "RFC7895" on these two pages:

• https://yangson.labs.nic.cz/yangson-man.html#yangson-man
• https://yangson.labs.nic.cz/datamodel.html

The string may appear on other pages too. These two listed pages are only the ones that come to my mind ;)

The ask is for Yangson to also support RFC 8525.

How to Identify which YL is Provided

Two ideas:

1. use an additional parameter/flag to indicate the YL's revision
2. auto-sense the YL-revision (i.e., is "modules-state" than 7895, else 8525)

How to Identify which Datastore is Use

This assumes that each datastore can be supported by an instance of yangson.DataModel.

Only one idea:

1. use an additional parameter/flag to indicate the datastore

Context

My RESTCONF server wishes to implement NMDA, in order to support the datastore described in draft-ietf-netmod-system-config, in order to support multi-tenancy (i.e., the 'host' system can share stuff with 'tenant' systems, that appear as data to the tenants.

Doing this with existing Yangson is a little awkward as my server MUST return RFC 8525 YL to clients, per RFC 8527, Section 2, and yet it doesn't consume that format itself. My code must maintain distinct instances of both YL revisions.

[llhotka]

I actually addressed this issue last week by a note in the documentation. The thing is that the 8525 format adds some complications, as you discuss above. I was thinking that the data model doesn't change that often so that an offline conversion utility might suffice. Could convert8525 help you?

[kwatsen]

Laugh. I wrote a similar thing yesterday. Now my Python code natively uses 8525 everywhere, and JIT-converts to 7895 just before calling DataModel(). That said, having convert8525 on the command line will help some of my command-line tests using Yangson to work too, so thank you for that!

Still, I wish Yangson had more native support....

FWIW, yanglint supports 8525-formated YL on the command line.