适配有无futureAvailability嵌套数组的Dynamic Jolt Spec实现问询

现有Jolt转换规则在输入包含futureAvailability嵌套数组时可正常生成预期输出，但当输入不含该数组时转换会失败，以下是兼容两种场景的实现方案：

输入示例 #

输入1（含futureAvailability数组） #

{
  "time": "2023-02-21T14:24:34.966Z",
  "itemId": "G20864_270",
  "unitOfMeasure": "PIECE",
  "futureAvailability": [
    {
      "availableQuantity": 200,
      "ETA": "2023-03-01T00:00:00.000Z"
    },
    {
      "availableQuantity": 201,
      "ETA": "2023-03-01T00:00:00.000Z"
    }
  ]
}

输入2（不含futureAvailability数组） #

{
  "time": "2023-02-22T09:13:52.168Z",
  "itemId": "G20824_510",
  "unitOfMeasure": "PIECE"
}

原Jolt规则（存在兼容性问题） #

[
  {
    "operation": "shift",
    "spec": {
      "futureAvailability": {
        "*": {
          "@(2,time)": "[&1].time",
          "@(2,itemId)": "[&1].itemId",
          "@(2,unitOfMeasure)": "[&1].unitOfMeasure",
          "ETA": "[&1].ETA",
          "availableQuantity": "[&1].availableQuantity"
        }
      }
    }
  }
]

兼容版Jolt规则 #

通过default操作给futureAvailability字段设置默认空数组，确保无论输入是否包含该字段，后续的shift操作都能正常执行：

[
  {
    "operation": "default",
    "spec": {
      "futureAvailability": []
    }
  },
  {
    "operation": "shift",
    "spec": {
      "futureAvailability": {
        "*": {
          "@(2,time)": "[&1].time",
          "@(2,itemId)": "[&1].itemId",
          "@(2,unitOfMeasure)": "[&1].unitOfMeasure",
          "ETA": "[&1].ETA",
          "availableQuantity": "[&1].availableQuantity"
        }
      }
    }
  }
]

验证结果 #

输入1的输出（与预期一致） #

[
  {
    "time": "2023-02-21T14:24:34.966Z",
    "itemId": "G20864_270",
    "unitOfMeasure": "PIECE",
    "ETA": "2023-03-01T00:00:00.000Z",
    "availableQuantity": 200
  },
  {
    "time": "2023-02-21T14:24:34.966Z",
    "itemId": "G20864_270",
    "unitOfMeasure": "PIECE",
    "ETA": "2023-03-01T00:00:00.000Z",
    "availableQuantity": 201
  }
]

输入2的输出（转换正常，输出空数组） #

[]

内容的提问来源于stack exchange，提问作者Thiyagaraj Narayanan