Source maps for CUE

[nessex]

With CUE, we get a lot of benefits out of using it to template and reduce boilerplate for our kubernetes configuration. However alongside this clear benefit, there is one minor downside: We lose the ability to easily discover where values come from in an automated way.

Specifically, automating changes to kubernetes configuration (such as resource limits & requests) when the source of truth is in CUE is very difficult as the language's flexibility allows those values to be in a large variety of places. We have to either build and enforce our own conventions to ensure they are in a consistent place, or use heuristics and testing output to validate that we guessed correctly.

It would be much nicer if we could generate a secondary file that tells us for each value where that value came from in the original source files.

In the Javascript bundling world, this is already common via source maps. Is there anything akin to source maps already existing for CUE? And if not, has it been considered at all as a possibility?