Implement format backend for "toon" format (https://github.com/toon-format/toon)

[cowtowncoder]

So, the new hotness wrt GenAI/LLMs is "toon", see: https://github.com/toon-format/toon (and in particular spec, https://github.com/toon-format/spec ).

Would be good to implement format backend, as part of jackson-dataformats-text, if feasible (and would appear it should be, on cursory glance).

[cowtowncoder]

Hmmmmmh. Looking at the spec, I am much less excited about this format -- sheer complexity of things smell like YAML. Not sure why author seems to have gotten carried away and added things like path folding... couldn't resist the big evil ("Root of most evil in format specs is the pre-mature complification").
Bah. Could have been nice format, but seems on its way to YAML^ng.

[pjfanning]

Jackson support for YAML uses Snakeyaml under the hood. Maybe a Toon equivalent Java lib could be use have Jackson Data Format support.

• https://github.com/toon-format/toon-java
• https://github.com/ricken07/toon4j
• https://github.com/arun-prabhakar/toon4j

All pretty new and not too many GitHub stars.

[cowtowncoder]

@pjfanning that is certainly a possibility, good suggestion.

EDIT: Asked Claude to evalute choices -- it considered 3rd one overall the best.

1. JToon: pre-1.0, encode-only -- probably not worth considering just for that
2. ricken07/toon4j -- otherwise many good qualities (including testing), but 0.1.0 (early). Requires jackson-databind that could be (but not necessarily) problematic (depending on nature of dep)
3. arun-prabhakar/toon4j -- Zero external dependencies - pure Java implementation (~80KB) (awesome if true); version 1.1.0 (may indicate maturity)

So we could start by evaluating (3) and see if that could be decent base.

[cowtowncoder]

Hmmmh. Alas, none of 3 support streaming (incremental) decoding. That is not great. Acceptable for casual usage but sub-optimal for performance-sensitive work.

Still, this is what TOML and Properties backends do, fwtw.

[prb]

Alrighty. I had some Claude capacity burning a hole in my pocket, so I had it whomp something up: @prb/jackson-toon

It doesn't use either JToon or toon4j (because neither of them is streaming).

[cowtowncoder]

A potential implementation by @prb

https://github.com/prb/jackson-toon

[pjfanning]

https://github.com/toon-format/toon-java has support (using Jackson) to convert from Toon text to JSON text and vice versa. So users who need support for the non-streaming features omitted by prb/jackson-toon could potentially use toon-format/toon-java to convert Toon to and from JSON and then use Jackson with the JSON. This approach let's you access Jackson support for annotations and for Kotlin/Scala and extra Java datatypes (Hibernate, Guava, etc).

[cowtowncoder]

@pjfanning That sounds like possible work-around if nothing else works, but is lossy and inefficient so if TOON is really being used, explicit format backend makes sense. Unfortunately with formats pipelines are not easily composable.

But I am still not quite convinced TOON is being adopted widely.