Conditional Fields | CUE

Field comprehensions can be used to add fields conditionally.

price: number

// High prices require a reason and the name of
// the authorising person.
if price > 100 {
	reason!:       string
	authorisedBy!: string
}

price: 200

$ cue export file.cue stock.yaml
authorisedBy: field is required but not present:
    ./file.cue:5:1
reason: field is required but not present:
    ./file.cue:5:1

When cue export processes multiple files it unifies their contents. The value of the price field in stock.yaml is available inside file.cue, and triggers the conditional inclusion of the required fields.