JSON Schema with infinite unknown property names-CodePudding

I want to create a JSON schema (v2020-12) which can validate design tokens
The problem here is, that those tokens could be nested infinitively and each nested property could have any name.

The schema should validate that a property can have either one other property with unknown name or a design token. Other properties should not be allowed.

This should be valid:

{
  "unknown_property_1": {
    "unknown_property_2": {
      << nesting with unknown depth >>
      "unknown_property_n": {
        "$value": "#fff",
        "$type": "this is a token with mandatory $value and $type"
      }
    }       
  }
}

This not:

{
  "unknown_property_1": {
    "fancy_unwanted_property": 123,
    "unknown_property_2": {
      "unknown_property_n": {
        "$value": "#fff",
        "$type": "this is a token with mandatory $value and $type"
      }
    }       
  }
}

I experimented with "anyOf" and "$ref" but couldnt get any close.

CodePudding user response：

Recursive structures can be defined quite elegantly in JSON Schema. Here's the simplest version.

{
  "type": "object",
  "properties": {
    "$value": { "type": "string" },
    "$type": { "type": "string" }
  },
  "additionalProperties": { "$ref": "#" }
}

If you need a more strict version, this is an alternative.

{
  "anyOf": [
    {
      "type": "object",
      "properties": {
        "$value": { "type": "string" },
        "$type": { "type": "string" }
      },
      "additionalProperties": false
    },
    {
      "type": "object",
      "patternProperties": {
        "": { "$ref": "#" }
      }
    }
  ]
}