Validate the existence of fieldA xor fieldB

[ChristianKniep]

I started with cue-lang and aim to use it to validate YAML. I want either to have a field called item or items, but not both and I am wondering how I can achieve that...

My cue file looks like this:

item?: string
items?: [...string]

And I suppose I need to add a check that checks if either of them is set, but not both.
(Writing the issue is almost rubber duck debugging - I might resolve the issue tomorrow already; hope that helps someone else)

Valid YAML

item: abc

or

items: [abc, cde]

Invalid YAML

item: abc
items: [abc, cde]

[seh]

See the numexist builtin function proposed in #822. It's not implemented today, but that's the intended way to cover this case.

[verdverm]

You could use the anyOf work around with an upper limit as well.

https://cuetorials.com/patterns/fields/#anyof

The oneOf pattern there may be sufficient for your needs however

val: {
  { item: string } | { items: [...string] }
}

https://cuelang.org/play/?id=gdbxOmzwmMy#cue@export@cue

[myitcv]

Thanks for raising this @ChristianKniep

@seh is right, this is covered in #822 so will close this as a duplicate.