如何在Terraform templatefile迭代中生成双JSON对象并修正ID索引

需要在Terraform的templatefile每次迭代中生成两个JSON对象，当前已能生成对应结构，但rule-id的索引无法实现连续递增。

原模板 #

${jsonencode({
  rules = flatten([
    [ for index, value in schemas : {
     "rule-type": "selection",
     "rule-id": "${index + 1}",
       "object-locator": {
         "schema-name": "${value}",
         "table-name": "%"
       },
     }
     ],
  ])
})}

调用代码 #

variable "schemas" {
  default = ["xxx", "yyy", "zzz"]
}

output "json_rules" {
  value = templatefile("${path.module}/rules.json.tpl", {
    schemas = var.schemas
  })
}

当前输出 #

{
  "rules": [
    {
      "object-locator": {
        "schema-name": "xxx",
        "table-name": "%"
      },
      "rule-id": 1,
      "rule-type": "selection"
    },
    {
      "object-locator": {
        "schema-name": "yyy",
        "table-name": "%"
      },
      "rule-id": 2,
      "rule-type": "selection"
    },
    {
      "object-locator": {
        "schema-name": "zzz",
        "table-name": "%"
      },
      "rule-id": 3,
      "rule-type": "selection"
    }
  ]
}

期望输出 #

{
  "rules": [
    {
      "object-locator": {
        "schema-name": "xxx",
        "table-name": "%"
      },
      "rule-id": 1,
      "rule-type": "selection"
    },
    {
        "rule-type": "transformation",
        "rule-id": "2",
        "rule-action": "rename",
        "rule-target": "schema",
        "object-locator": {
            "schema-name": "xxx"
        },
        "value": "xxx"
    },
    {
      "object-locator": {
        "schema-name": "yyy",
        "table-name": "%"
      },
      "rule-id": 3,
      "rule-type": "selection"
    },
    {
        "rule-type": "transformation",
        "rule-id": "4",
        "rule-action": "rename",
        "rule-target": "schema",
        "object-locator": {
            "schema-name": "yyy"
        },
        "value": "yyy"
    },
    {
      "object-locator": {
        "schema-name": "zzz",
        "table-name": "%"
      },
      "rule-id": 5,
      "rule-type": "selection"
    },
    {
        "rule-type": "transformation",
        "rule-id": "6",
        "rule-action": "rename",
        "rule-target": "schema",
        "object-locator": {
            "schema-name": "zzz"
        },
        "value": "zzz"
    }
  ]
}

编辑1：结构正确但索引错误的尝试 #

修改后的模板 #

${jsonencode({
  rules = flatten([
    [ for index, value in schemas : [
    {
        "rule-type": "selection",
        "rule-id": index + 1,
        "object-locator": {
            "schema-name": "${value}",
            "table-name": "%"
       }
     },
    {
       "rule-type": "transformation",
       "rule-id": index + 2,
       "rule-action": "rename",
       "rule-target": "schema",
       "object-locator": {
            "schema-name": "${value}"
       }
     }]
     ],
  ])
})}

修正后输出（索引错误） #

{
  "rules": [
    {
      "object-locator": {
        "schema-name": "xxx",
        "table-name": "%"
      },
      "rule-id": 1,
      "rule-type": "selection"
    },
    {
      "object-locator": {
        "schema-name": "xxx"
      },
      "rule-action": "rename",
      "rule-id": 2,
      "rule-target": "schema",
      "rule-type": "transformation"
    },
    {
      "object-locator": {
        "schema-name": "yyy",
        "table-name": "%"
      },
      "rule-id": 2,
      "rule-type": "selection"
    },
    {
      "object-locator": {
        "schema-name": "yyy"
      },
      "rule-action": "rename",
      "rule-id": 3,
      "rule-target": "schema",
      "rule-type": "transformation"
    },
    {
      "object-locator": {
        "schema-name": "zzz",
        "table-name": "%"
      },
      "rule-id": 3,
      "rule-type": "selection"
    },
    {
      "object-locator": {
        "schema-name": "zzz"
      },
      "rule-action": "rename",
      "rule-id": 4,
      "rule-target": "schema",
      "rule-type": "transformation"
    }
  ]
}

解决方案 #

问题核心是rule-id的计算逻辑错误：每个schema对应两个规则，需基于索引计算出连续递增的ID。修改后的模板如下：

${jsonencode({
  rules = flatten([
    for index, value in schemas : [
      {
        "rule-type": "selection",
        "rule-id": index * 2 + 1,
        "object-locator": {
          "schema-name": value,
          "table-name": "%"
        }
      },
      {
        "rule-type": "transformation",
        "rule-id": index * 2 + 2,
        "rule-action": "rename",
        "rule-target": "schema",
        "object-locator": {
          "schema-name": value
        },
        "value": value
      }
    ]
  ])
})}

关键调整说明 #

1. ID计算逻辑：利用从0开始的index，每个schema的两个规则ID分别为index*2+1和index*2+2，确保ID连续唯一。
2. 简化变量引用：去掉不必要的字符串插值${value}，直接使用变量value，jsonencode会自动处理字符串转义。
3. 补全缺失字段：给transformation规则添加了期望输出中要求的value字段。

内容的提问来源于stack exchange，提问作者Theo Sweeny