undefined fields shouldn't be used when checking enum

[wavern1]

If a field is undefined and the schema specifies it as being an enum, it errors out saying "must be an enum value".

I think the logical approach here would be to skip that field unless isRequired is set to true on it as well

[LinusU]

Yeah, the same is true when type: ['null', 'string'], enum: ['a', 'b'], null is not accepted. Unfortunately I think that this is a part of the JSON Schema specification so I'm not sure that we could change it.

If someone could quote the spec on how this should be handled I'd be happy to fix it 👍

[RangerMauve]

I think the main issue is that undefined isn't a valid JSON value, so the spec wouldn't have anything to say on the matter.

In my opinion, undefined should be treated the same as the key not existing, since it would disappear when the object got serialized to JSON.

[LinusU]

Ah, of course, that is true. Yeah, I also think that we should treat undefined as the value isn't there...

[RangerMauve]

It'll probably make calculating minProperties and maxProperties more annoying. :P