Yeah similarly I'm using Nix to template K8s templates and I've never looked back. Helm is great for deploying 3rd party applications easily but I've never seen the appeal for using it for in house services, templating YAML is gross indeed.

I was reading the description of Jsonnet and wondering why we don't just use JavaScript. Read a file, evaluate it, take the value of the last expression as the output, and blat it out as JSON.

The environment could be enriched with some handy functions for working with structures. They could just be normal JavaScript functions. For example, a version of Object.assign which understands that "key+" syntax in objects. Or a function which removes entries from arrays and objects if they have undefined values, making it easy to make entries conditional.

Those things are simple enough to write on demand that this might not even have to be a packaged tool. Just a thing you do with npm.

The fact that it's a purely functional programming language with lazy evaluation is really powerful but steepens the learning curve for devs who haven't worked with functional languages.

The stdlib is also pretty sparse, missing some commonly required functions.

> The fact that it's a purely functional programming language with lazy evaluation is really powerful but steepens the learning curve for devs who haven't worked with functional languages.

does it really though? what part do they struggle with?

IME engineers struggle with folds most.

> The stdlib is also pretty sparse, missing some commonly required functions.

This seems to be the general curse of template languages. For some reason, their authors have this near-religious belief in removing every "unneeded" feature, which in practice results in having to write 10 incomprehensible lines of code to do something that could be easily done in one line of readable code in a proper PL.