Re: [netmod] IETF 108: Summary of insignificant whitespace changes and versioning

Ladislav Lhotka <ladislav.lhotka@nic.cz> Wed, 12 August 2020 09:08 UTC

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From: Ladislav Lhotka <ladislav.lhotka@nic.cz>
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Subject: Re: [netmod] IETF 108: Summary of insignificant whitespace changes and versioning
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On 12. 08. 20 11:02, Martin Björklund wrote:
> "Rob Wilton (rwilton)" <rwilton@cisco.com> wrote:
>>
>>
>>> -----Original Message-----
>>> From: netmod <netmod-bounces@ietf.org> On Behalf Of Ladislav Lhotka
>>> Sent: 12 August 2020 08:43
>>> To: Martin Björklund <mbj+ietf@4668.se>
>>> Cc: jclarke=40cisco.com@dmarc.ietf.org; netmod@ietf.org
>>> Subject: Re: [netmod] IETF 108: Summary of insignificant whitespace
>>> changes and versioning
>>>
>>> Martin Björklund <mbj+ietf@4668.se> writes:
>>>
>>>> Hi,
>>>>
>>>>
>>>> Ladislav Lhotka <ladislav.lhotka@nic.cz> wrote:
>>>>>
>>>>>
>>>>> On 11. 08. 20 15:41, Joe Clarke (jclarke) wrote:
>>>>>> At the IETF 108 virtual meeting, Lada asked about what would happen
>>> if he converted a YANG module to YIN syntax (or vice versa, or to some
>>> other format).  This was during the discussion of the issue of what
>>> should
>>> happen if a module changes and the only changes are insignificant
>>> whitespaces (e.g., strip trailing spaces, change line length of
>>> descriptions, etc.).
>>>>>>
>>>>>> The authors/contributors discussed on this on our weekly calls, and
>>> we propose:
>>>>>>
>>>>>> If a module changes and those changes are only insignificant
>>> whitespace changes and the syntax of the module remains the same
>>> (i.e.,
>>> YANG to YANG, YIN, YIN, etc.), a new revision of the module MUST be
>>> created.  If you are using YANG semver as your revision scheme, you
>>> MUST
>>> apply a PATCH version bump to that new module revision to indicate an
>>> editorial change.
>>>>>>
>>>>>> The reasoning behind this decision is that it makes it very clear and
>>> unambiguous to consumers that this module has been consciously
>>> changed,
>>> and those changes are only editorial.  This way one won’t be concerned
>>> if
>>> they note that a module of a given syntax with the same version but
>>> different checksums and diffs wasn’t otherwise manipulated.
>>>>>>
>>>>>> That said, if a module changes format from one syntax to another but
>>> maintains semantic equivalency, then the revision and YANG semver MUST
>>> be
>>> the same.  In that case, one will use the extension to realize that
>>> this
>>> module file cannot be directly compared to one of another syntax
>>> without
>>> looking at compiled or semantic representation.
>>>>>
>>>>> The last paragraph means that after a round trip YANG -> YIN -> YANG
>>> the
>>>>> initial and final YANG modules MUST have the same revision. However,
>>>>> depending on the conversion tools used, they may easily differ in
>>>>> whitespace, so their byte-oriented checksums won't be equal.
>>>>>
>>>>> I think there are in fact three cases:
>>>>>
>>>>> 1. Whitespace outside statement arguments - I believe this should
>>>>> never
>>>>> be significant.
>>>>
>>>> Agreed.
>>>>
>>>>> 2. Whitespace in the argument of "contact", "description",
>>>>> "error-message" and "organization" - this is tricky because tools may
>>>>> format such arguments differently. I am leaning towards making
>>>>> whitespace insignificant in this case as well.
>>>>>
>>>>> 3. Whitespace in other arguments has to be significant and lead to a
>>>>> revision bump.
>>>>
>>>> I think that any change in an argument string is an editorial change.
>>>>
>>>> For example, compare these two changes:
>>>>
>>>>    A1.  description "a server.";
>>>>    A2.  description "A server.";
>>>>
>>>>    B1.  description "A  server.";
>>>>    B2.  description "A server.";
>>>>
>>>> These are editorial changes, and thus the revision should be changed.
>>>
>>> But consider
>>>
>>>    description
>>>        "A server and
>>>         its data.";
>>>
>>> versus
>>>
>>>    description
>>>        "A server and
>>>        its data.";
>>>
>>> Here the difference is only in presentation - a YANG parser gives the
>>> same
>>> string in both cases. Another awkward case is whitespace before a line
>>> break.
>> [RW] 
>>
>> [As an individual contributor]
>>
>> What about:
>>
>>     description
>>         "A server and
>>          its data.";
>>  
>> versus
>>  
>>     description
>>         "A server and its data.";
> 
> I wrote:
> 
>>>> I think that any change in an argument string is an editorial change.
> 
> Your example changes the argument string; hence this is a significant
> (editorial) change, and requires a new revision.

Perhaps formally, but given the role that the description statement
plays reflowing really means no change.

Lada

> 
>> Or any cases where description statements might be reflowed by tooling
>> to fit different line width limits?
> 
> See above.
> 
> 
> 
> /martin
> 
> 
>>
>> Regards,
>> Rob
>>
>>
>>>
>>> Lada
>>>
>>>>
>>>> Note however that the following change might look like an editorial
>>>> whitespace change in the argument, but in fact it is not:
>>>>
>>>>   C1.
>>>>       description
>>>>           "A server and
>>>>            its data.";
>>>>
>>>>   C2.
>>>>       description
>>>>         "A server and
>>>>          its data.";
>>>>
>>>>
>>>> /martin
>>>>
>>>>
>>>>>
>>>>> And one more corner case for both 2 a 3: what if "\t" is replaced with
>>>>> the tab character in a double-quoted string? For YANG, these two
>>> strings
>>>>> are absolutely equivalent.
>>>>>
>>>>> Lada
>>>>>
>>>>>>
>>>>>> Thoughts?
>>>>>>
>>>>>> Joe
>>>>>> _______________________________________________
>>>>>> netmod mailing list
>>>>>> netmod@ietf.org
>>>>>> https://www.ietf.org/mailman/listinfo/netmod
>>>>>>
>>>>>
>>>>> --
>>>>> Ladislav Lhotka
>>>>> Head, CZ.NIC Labs
>>>>> PGP Key ID: 0xB8F92B08A9F76C67
>>>>>
>>>>> _______________________________________________
>>>>> netmod mailing list
>>>>> netmod@ietf.org
>>>>> https://www.ietf.org/mailman/listinfo/netmod
>>>
>>> --
>>> Ladislav Lhotka
>>> Head, CZ.NIC Labs
>>> PGP Key ID: 0xB8F92B08A9F76C67
>>>
>>> _______________________________________________
>>> netmod mailing list
>>> netmod@ietf.org
>>> https://www.ietf.org/mailman/listinfo/netmod

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