Cue, an open-source data validation language

Re:Cue, an open-source data validation language by sdboyer on Tuesday June 15, 2021 @11:32AM (#27516946)

I'd say all of these problems have answers in CUE.

> I want to be able to write a "generic environment" module for each application and then parameterize it accordingly for each environment.

This is pretty solidly in the target use case range, i'd say - managing variations of the same "object type" over some dimension is a lot of what's targeted by the way that CUE treats directory hierarchies when loading files: https://cuelang.org/docs/concepts/packages/#instances

The main thing you have to consider in designing a layout is that you have to take a compositional approach to how you define individual config instances. That is, you can't start from prod's config, then override a value or two for staging.

If i were to do it - i have not, this is not how i currently use CUE - my first approach would probably be by defining defaults at the "policy" level (per the above link), which effectively allows you to get exactly one "override"-ish behavior.

Lots of possible approaches to this, though.

> but you can't quite emulate functions as far as I can tell

Function-like capability is present, just in a form that's less familiar. I think of them as "function structs." This post has a bunch of examples https://github.com/cuelang/cue/issues/139#issuecomment-55677.... It seems there's a plan to add a more comfortable notation (https://github.com/cuelang/cue/issues/943), but it's fundamentally possible now.

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Re:Cue, an open-source data validation language by throwaway894345 on Tuesday June 15, 2021 @11:37AM (#27517009)

Consider this example: https://github.com/cuelang/cue/discussions/967

How would you solve this with directory structure and "function structs" respectively? I'm having trouble wrapping my head around the former and ran into shadowing problems with the latter.

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Re:Cue, an open-source data validation language by dqpb on Tuesday June 15, 2021 @12:37PM (#27517887)

I would do it like this:

test.cue:

    #Job: {
        command: string
        args: string
        cli: "\(command) \(args)"
    }

    #GoJob: #Job & {
        command: "go"
    }

    #GoJobV: #GoJob & {
        args: "-v ./..."
    }

    job: #GoJobV.cli

Results in:

  $ cue export test.cue 
  {
      "job": "go -v ./..."
  }

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