How to specify unlimited maximum arity?

[patriksvensson]

If an argument takes an unlimited number of values, what should the maximum arity be set to?

{
  "arguments": [
    {
      "name": "FOO",
      "arity": {
        "minimum": 0,
        "maximum": ?
      }
    }
  ]
}

[baronfel]

Make the property nullable, and a null/undefined property represents no bound?

[patriksvensson]

Yes, that seems reasonable!

[reitzig]

So

required: true

and

arity:
  minimum: 1

have different meaning? 🤔 Or is arity.maximum: null (aka infty) implicit in both cases? Which would beg the question: In the first case, the implicit value if arity.minimum would be 1, whereas with required: false it'd be 0? So,

required: false
arity:
  minimum: 1

means ... what? Or is it invalid?

Hang on ... what are the intended defaults for required and arity? The spec doesn't say.

Seems to me like required is redundant (at least for arguments). With defaults arity.minimum: 1 and arity.maximum: 1, the default would be "required singleton" (arguably the most common case for arguments?). To make it optional, set arity.maximum: 0; for multiple values, set e.g. arity.maximum: 77; for arbitrarily many values, set arity.maximum: null.

Caveat: IIRC, "missing value" and "value set to null" can't be properly distinguished in JSON schema; the interaction with required can be weird, if I recall, and I'm not sure about default. It may be prudent to allow a single string "infinity" or "unlimited" as additional value for arity.maximum, but forbid null.