[ithkuil]

I once built a mandelbrot fractal renderer which emitted a data-URL encoded PNG string to stdout in BCL (a spiritual predecessor of Jsonnet @ Google).

Yeah, I know what you mean. It lacks generic input/output, you cannot read write arbitrary files and perform arbitrary network requests etc.

I do like that restriction in the context of managing configuration systems, because it allows you to build hermetic evaluations.

With kubecfg we added the ability to import from URLs, which I wish was available out of the box in jsonnet.