support schemas for empty arrays

[mfulton26]

I need to validate that an array is present and empty under certain scenarios. I tried "items": [] but that produces and "invalid" schema: data.items should NOT have fewer than 1 items (AJV errorsText)

i.e. I'd like to do the following:

{ "type": "array", "items": [] }

or maybe:

{ "type": "array", "items": false }

But I had to do this instead (maybe there is a better way?):

{ "type": "array", "maxItems": 0 }

[Relequestual]

What's wrong with maxItems?

[notEthan]

"items": false does what you want. you could also do "const": [] or maxItems.

[mfulton26]

hmmm, const seems nice

I suppose nothing is really wrong with maxItems: 0 it just wasn't what I thought of first and I was surprised when I was informed that items: [] wasn't valid

[mfulton26]

[1, 2, 3] validates for me against items: false using ajv which was unexpected

[Relequestual]

That's strange... Looks like items: false against [1,2,3] works for me.
https://jsonschema.dev/s/SEUZM

The instance would be valid if the array was empty, because the subschema value of items is applied to each value in the applicable array.

[Relequestual]

const may also be a good option, as without it, you'll need to define type in order to make the value IS an array in the first place, as you have done.

[mfulton26]

this might be a bug in Ajv

ajv-validator/ajv#1270

thanks

[Relequestual]

OK. Weird. My site uses a version of ajv, but probably not the latest... =/

[mfulton26]

@Relequestual it only seems to be an issue when Ajv is configured with strictKeywords: true