Re: [netmod] RFC 7951

Hi Jack,

Yes, indeed, I did misunderstand your original #2.

Between an empty list node appearing (as just "[ ]") versus not appearing at all, I do not think that the JSON encoding is defined, and so tooling should accept either encoding, IMO.   [FWIW, XML has only one encoding].

Personally, I initially preferred #1 (because it is more self-describing), but implementation-details drove me to #2.

Kent // contributor

> On Mar 29, 2022, at 2:19 PM, Jack Rickard <jack.rickard@microsoft.com> wrote:
> 
> Hi Kent,
> 
> Thanks very much for the response. However, I'm slightly worried you've misunderstood my examples, and as I've been fighting in the #1 corner I want to make sure I give #2 a fair chance.
> 
> Given this schema:
> module test {
>   prefix "test";
>   namespace "urn:test";
> 
>   container test {
>     leaf foo {type string;}
>     leaf-list bar {type string;}
>     leaf baz {type string;}
>   }
> }
> 
> Is this valid (#1):
> {
>         "test:test": {
>                 "foo": "test1",
>                 "bar": [],
>                 "baz": "test2"
>         }
> }
> 
> and is this valid (#2):
> {
>         "test:test": {
>                 "foo": "test1",
>                 "baz": "test2"
>         }
> }
> 
> To make sure I didn't miss something I verified this with yanglint 0.16.105 (what ubuntu gave me), and that accepts #2 but not #1 (it rejects #1 with err : Invalid JSON data (unexpected value). (/test:test/bar)).
> To be really clear this is accepted:
> {
>         "test:test": {
>                 "foo": "test1",
>                 "bar": ["test3"],
>                 "baz": "test2"
>         }
> }
> 
> Thanks,
> Jack
> 
> From: Kent Watsen <kent+ietf@watsen.net>
> Sent: 29 March 2022 18:14
> To: Jack Rickard <jack.rickard@microsoft.com>
> Cc: draft-ietf-netmod-yang-json@ietf.org <draft-ietf-netmod-yang-json@ietf.org>; netmod@ietf.org <netmod@ietf.org>
> Subject: Re: [netmod] RFC 7951 - JSON encoding of empty lists
>  
> #1 is an empty list (or leaf-list).  This is what you want.
> 
> #2 is a list containing one element, which is an empty container (or, in Python term's, an empty 'dict').
> 
> Yanglint 1.x used to accept #1, kinks are being worked out on the 2.x branch.
> 
> Kent // contributor
> 
> 
>> On Mar 29, 2022, at 10:21 AM, Jack Rickard <jack.rickard=40microsoft.com@dmarc.ietf.org <mailto:jack.rickard=40microsoft.com@dmarc.ietf.org>> wrote:
>> 
>> Hi,
>>  
>> I think I’ve found an ambiguity in RFC 7951, and I’d like your input on what was intended and what the best behaviour to exhibit is.
>>  
>> Section 5.3 and 5.4 of RFC 7951 - JSON Encoding of Data Modeled with YANG (ietf.org) <https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fhtml%2Frfc7951%23section-5.3&data=04%7C01%7Cjack.rickard%40microsoft.com%7Ca33f2d22f70f4de7a87808da11a79ae4%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637841709447361395%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=2jqJW1VVJyft9CVC3T5xCgXvlt4Zsd7c7mdtBrKSpdM%3D&reserved=0> describe the encoding of leaf-lists and lists, however it’s unclear how an empty list should be encoded. Should it be encoded as:
>> An empty array: {“list”: []}
>> A missing field: {}
>>  
>> I’ve seen libraries go either way, libyang only accepts 2 but the python yangson library accepts both (I’m not sure which is the default).
>>  
>> Thanks,
>> Jack Rickard 
>> he/him 
>> Software Engineer 
>> jack.rickard@microsoft.com <mailto:jack.rickard@microsoft.com> 
>> 
>> <image001.png>
>>  
>>  
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