rules_jsonnet VS jk

I can definitely sympathize here - in every context, just straight JSON/YAML configuration seems never expressive enough, but the tooling created in response always seems to come with sharp edges.

Here are some of the things I appreciate about Jsonnet:

- It evals to JSON, so even though the semantics of the language are confusing, it is reasonably easy to eval and iterate on some Jsonnet until it emits what one is expecting - and after that, it's easy to create some validation tests so that regressions don't occur.

- It takes advantage of the fact that JSON is a lowest-common-denominator for many data serialization formats. YAML is technically a superset of JSON, so valid JSON is also valid YAML. Proto3 messages have a canonical JSON representation, so JSON can also adhere to protobuf schemas. This covers most "serialized data structure" use-cases I typically encounter (TOML and HCL are outliers, but many tools that accept those also accept equivalent JSON). This means that with a little bit of build-tool duct-taping, Jsonnet can be used to generate configurations for a wide variety of tooling.

- Jsonnet is itself a superset of JSON - so those more willing to write verbose JSON than learn Jsonnet can still write JSON that someone else can import/use elsewhere. Using Jsonnet does not preclude falling back to JSON.

- The tooling works well - installing the Jsonnet VSCode plugin brings in a code formatter that does an excellent job, and rules_jsonnet[0] provides good bazel integration, if that's your thing.

I'm excited about Jsonnet because now as long as other tool authors decide to consume JSON, I can more easily abstract away their verbosity without writing a purpose-built tool (looking at you, Kubernetes) without resorting to text templating (ahem Helm). Jsonnet might just be my "one JSON-generation language to rule them all"!

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Though if Starlark is your thing, do checkout out skycfg[1]

[0] - https://github.com/bazelbuild/rules_jsonnet

[1] - https://github.com/stripe/skycfg

People have tried: https://github.com/jkcfg/jk

But yeah I agree. The thing is, if all you need is robust determinism why do you need a full functional language with currying and other complex concepts?

Google had the same problem for Bazel, and their solution (Starlark) is way easier to understand.

If I were writing a build system today (and I did just write one actually to test out some ideas) I would use Typescript for the language with something like jk to provide hermeticity. Typescript has many advantages, especially over Python, but mainly:

It's possible to sandbox most languages, and with some work you can probably make them deterministic too.

Here's an example: https://github.com/jkcfg/jk

That beats having to learn an entirely new language.

Maybe Javascript? A lot of web tools support Javascript config files. There's this nice-looking effort to provide a hermetic execution environment for them: https://github.com/jkcfg/jk and if you use Typescript you get an extremely good static type system too. Plus the language is already very well known with loads of tool support and documentation.

Definitely what I would use today.

If you think "but I need conditionals and file inclusion and ..." then maybe consider just allowing a full programming language instead. Someone pointed me to jk which looks like it is heading in the right direction, except that it outputs YAML by default for some insane reason.

You may be interested in jk. If you don't want to use a special purpose configuration language (jsonnet, cue, dhall, etc), this is a nice alternative that uses js in a hermetic runtime (but see their open issues for progress on that). They seem to also be adding native typescript support so you could even have type checking built-in.