Use object property keys as enum in JSON schema - json

Question

I'm trying to validate a JSON file using JSON Schema, in order to find cases of "broken references". Essentially my file consists of items and groups, with each item belonging to a single group referenced by the groups property key, like so:
{
"items": {
"banana": {
"name": "Banana",
"group": "fruits"
},
"apple": {
"name": "Apple",
"group": "fruits"
},
"carrot": {
"name": "Carrot",
"group": "vegetables"
},
"potato": {
"name": "Potato",
"group": "vegetables"
},
"cheese": {
"name": "Cheese",
"group": "dairy"
}
},
"groups": {
"fruits": {
"name": "Fruits"
},
"vegetables": {
"name": "Vegetables"
}
}
}
In the example above the item cheese is to be considered invalid, as there are no dairy property in the groups object. I've tried to validate this using the following schema:
{
"$schema": "http://json-schema.org/draft-06/schema#",
"title": "Food",
"id": "food",
"type": "object",
"properties": {
"items": {
"type": "object",
"patternProperties": {
"^[A-Za-z0-9-_.:=]+$": {
"properties": {
"name": {
"type": "string",
"pattern": "^[A-Za-z- ]+$"
},
"group": {
"pattern": "^[a-z]+$",
"enum": {
"$data": "/groups"
}
}
}
}
}
},
"groups": {
"type": "object",
"patternProperties": {
"^[A-Za-z0-9-_]+$": {
"properties": {
"name": {
"type": "string",
"pattern": "^[A-Za-z- ]+$"
}
}
}
}
}
},
"additionalProperties": false
}
This has the effect that the enum for group is populated by the property values in groups, but what I want to do is use the property keys defined in groups.
If I add a property like e.g. groupIds and let that be an array of all property keys found in groups and specify the enum as "$data": "/groupIds" it does work, so I take this to be a JSON pointer issue.
The enum keyword in JSON Schema is defined as:
The value of this keyword MUST be an array. This array SHOULD have at least one element. Elements in the array SHOULD be unique.
So if I could only get JSON pointer to reference an object's keys rather than its values I guess the enum validation would just work. I'm thinking something like "$data": "/groups/.keys", "$data": "/groups/$keys" or similar, but haven't found it while googling or reading the spec. Is there such a thing or has it ever been proposed?

Answer 1

There is no such thing. It’s very close to general expressions inside JSON and it may have some use cases, but there is no such specification.