Dynamic JSON Schema Defaults

variables.json

{
  "title": "root",
  "type": "object",
  "definitions": {
    "emailShareSubject": {
      "type": "string",
      "description": "Email share subject",
      "minLength": 4
    },
    "emailShareSubjectCREDIT": {
      "default": "Get ${{math programDetails.referredRewardDetails.credit ' / 100'}} off {{companyName}}"
    },
    "emailShareSubjectTIME_CREDIT": {
      "default": "Get {{programDetails.referredRewardDetails.credit}} month(s) of free {{companyName}}"
    },
    "emailShareSubjectPCT_DISCOUNT": {
      "default": "Get {{companyName}} for {{programDetails.referredRewardDetails.discountPercent}}% less!"
    }
  },
  "properties": {
    "shareMessaging": {
      "title": "Share Messaging",
      "type": "object",
      "properties": {
        "emailShareSubject": {
          "allOf": [
            { "$ref": "#/definitions/emailShareSubject" },
            { "$ref": "#/definitions/emailShareSubject{{programDetails.referredRewardDetails.rewardType}}" }
          ]
        }
      }
    }
  }
}