jrsonnet VS starlark-go

Jsonnet does all that you wanted in your ideal config language, and has a rust implementation too: https://github.com/CertainLach/jrsonnet

> jsonnet seemed like a great idea to me, but I've experienced extremely low performance.

Although each implementation of jsonnet has some quirks, take a look at (scala-based) sjsonnet^1 or go-jsonnet^2 for improved performance. We use go-jsonnet because of some issues we had with the scala version - but it does seem to be the fastest by a large margin.

There's also a Rust version^3 that claims to be the fastest yet^4, but I haven't experimented with it at all.

[1]: https://github.com/databricks/sjsonnet

[2]: https://github.com/google/go-jsonnet/

[3]: https://github.com/CertainLach/jrsonnet

[4]: https://gist.github.com/CertainLach/5770d7ad4836066f8e0bd91e...

Starlark in go https://github.com/google/starlark-go is a great way to combine the best of both, the ease of use of Python and the simplicity of go.

I have been building a platform for deploying internal web applications using this approach https://github.com/claceio/clace. Use Starlark to configure the application, the platform itself is built in go.

The big unknown is your task definition: what does user-defined logic look like? If you're expecting go code, that's gonna need some cleverness because of the compiled nature of it. There's a node runtime implemented in go if you want to provide sandboxed javascript (check the source of k6.io, it's the main one I know that uses it). If you want to provide building blocks and let them compose them, starlark might be a good choice.

Another one of those (with broader language support) is the Starlark language, which has a Go implementation: https://github.com/google/starlark-go

Every config format gets as complex to be touring complete in the end. We had similar problems and eventually got rid of that complexity and switched to starlark (the bazel config language), was a huge benefit for the tools. https://github.com/google/starlark-go "Starlark is a dialect of Python intended for use as a configuration language. Like Python, it is an untyped dynamic language with high-level data types, first-class functions with lexical scope, and garbage collection."

Direct link to the Go implementation of Starlark: https://github.com/google/starlark-go

For a Python-like syntax, https://github.com/google/starlark-go is the language used in Babel. It's very mature, but since it is used in a massive mature project with a specific purpose, it doesn't move fast or drift from the spec of its Java-based sibling. It doesn't have exception try except blocks or some other features you might expect, but for short extension logic, it might be exactly what you want with the stability you can depend upon.

Context: https://github.com/google/starlark-go/blob/cfacd890221418a2dc2c736f7b5e3476c38709b1/starlark/int_posix64.go

Thus envd is more like Dockerfile, while it uses a simplified python dialect starlark https://github.com/google/starlark-go as the build language.

Use Go (mostly for starlark-go)