Re: yaml-cpp and YAML 1.2

Very well stated, Oren. A couple points of possible current interest:

   - I have recently started what I call the yaml-dev-kit
   <https://github.com/ingydotnet/yaml-dev-kit#readme>
   - See YAML Loader Guide
   <https://github.com/ingydotnet/yaml-dev-kit/blob/guide/yaml-loader-guide.pod#readme>
   - https://github.com/ingydotnet/yaml-pegex-pm/ is a new project
   currently using the dev kit for tests
   - Also https://github.com/flyx/NimYAML
   - Catch flyx, ingy (always) and obk, andrey-snakeyaml (sometimes) on
   irc.freenode.net#yaml to discuss


On Fri, Mar 4, 2016 at 4:00 AM, Oren Ben-Kiki <[email protected]> wrote:

> The main change from 11 to 1.2 was JSON compatibility and very few other
> very minor syntax simplifications. All the schema flexibility , the layered
> processing model, and the data models were there from from YAML1.0 - this
> is the essence of YAML, IMO, even more than the syntax.
>
> As for the specific recommended schemas, we made more explicit what was
> inherent in the system. We put 3 schemas directly in the spec, because
> these schemas are "important", not because they are "all encompassing". The
> failsafe schema allows you to process _any_ YAML document, regardless of
> who generated it. That is "good". The JSON-compatible schema is important
> for obvious reasons. The "Core" schema is intended to be a, well, "core"
> for more specific schemas that step beyond JSON compatibility.
>
> As Ingy correctly pointed out, we made a big mistake by not updating the
> type repository to match. Still, the fact the above 3 schemas are directly
> in the spec serves to say (1) "there is more then one", and at the same
> time (2) "here is how to maximize interoperability".
>
> Obviously, different applications use different schemas. Consider the
> schema used by Ruby's yaml module (which I use a lot). It supports
> ruby-specific tags that are obviously not supported by SnakeYAML, and
> vice-versa. There's no expectation that I'll dump my Ruby data into YAML
> and load it into some random Java application and that my Ruby classes will
> just magically migrate as a result.
>
> Instead what we can do is run a Java YAML composer, which will give me a
> (complete or partial) representation as abstract YAML nodes - basically,
> what yaml-cpp does. Then I can load YAML generated by anyone at all, and do
> _some_ stuff with it. Obviously not as much stuff as the Ruby application
> that generated this YAML. And that's OK, and it demonstrates why YAML tools
> that do not go "all the way" play an important role in the ecosystem.
>
> This is why I talked about "controlling" interoperability, which is
> doable, rather than "ensuring" it, which is not possible in general.
>
> If SnakeYAML correctly parses all the examples, and in general follows the
> 1.2 spec, syntax-wise, and doesn't violate the 1.* specs,
> information-model-wise (e.g., it must not use keys order, it must ignore
> the node style when doing tag resolution, etc.), then as far as I'm
> concerned, it is 1.2 compliant.
>
> Note that the examples were not meant to be a comprehensive set of unit
> tests for testing compliance. So I don't have a set of "YAML certification
> tests" to point you at. Sorry :-(
>
> I did set up ypaste (which is up and running again) to serve as a dynamic
> reference in case there are edge cases one wants to investigate. But that
> only covers the _syntax_. It won't help you with testing the tag resolution
> rules.
>
> Creating a YAML certification test suite is an interesting project. It
> would be great if someone picked that one up. I don't have the time :-(
>
> I greatly appreciate you putting the time and effort into SnakeYAML and
> updating it to YAML1.2. The more implementations the merrier, and the more
> they stick with the spec, the better.
>
> Thanks,
>
> Oren.
>
> On Fri, Mar 4, 2016 at 12:44 PM, Andrey Somov <[email protected]>
> wrote:
>
>> Dear Oren,
>> thank you for the time and patience.
>>
>> 1. I am sorry, I messed the terminology. I was saying "parser", but was
>> meaning "processor". I have already fixed the terminology on SnakeYAML's
>> page to avoid confusion. SnakeYAML is a complete processor, not merely a
>> parser.
>> But PyYAML still says "PyYAML - The next generation YAML parser and
>> emitter for Python.", while in fact it is also composer and constructor.
>> Which means PyYAML is a processor.
>>
>> 2. I completely misunderstood the recommended schemas. I must admit I
>> still do not understand them. Especially I do not get what is changed in
>> 1.2 from 1.1. Flexible tag resolution was already there in 1.1.
>>
>> 3. At the moment SnakeYAML implements 1.1 and there is no single bug
>> related to the spec compliance.
>> Users ask to implement 1.2. If SnakeYAML can parse all the examples of
>> YAML 1.2 without failures, is it  1.2 compliant ?
>> If yes, then why the spec contains the schemas definitions ?
>> What is the indication that SnakeYAML processor implements recommended
>> schemas as it should ?
>>
>> Cheers,
>> Andrey
>>
>
>
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