JSON Schema时区选择验证需求：单时区选择需判定为合法

我需要一个用于输入字段验证的JSON Schema，实现时区选择功能，所有可选时区都要存在Schema里。现在遇到的问题是：当某个大洲（比如Africa）下有多个时区时，只选该大洲下的单个时区会被判定无效，但下面这段JSON应该是有效的：

{
  "continents": [
    {
            "continent": "Africa",
            "timezones": [
              {
                "timezone": "Africa/Abidjan",
                "utc_offset": "+00:00",
                "dst_offset": "+00:00"
              }
      ]
    }
  ]
}

而当大洲下只有一个时区（比如UTC）时，当前Schema能正确判定有效性。以下是我目前用的简化版Schema：

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "Continents Timezones",
  "type": "object",
  "properties": {
    "continents": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "continent": {
            "type": "string"
          },
          "timezones": {
            "type": "array",
            "items": {
              "type": "object",
              "properties": {
                "timezone": {
                  "type": "string"
                },
                "utc_offset": {
                  "type": "string"
                },
                "dst_offset": {
                  "type": "string"
                }
              },
              "required": [
                "timezone",
                "utc_offset",
                "dst_offset"
              ]
            }
          }
        },
        "required": [
          "continent",
          "timezones"
        ],
        "enum": [
          {
            "continent": "Africa",
            "timezones": [
              {
                "timezone": "Africa/Abidjan",
                "utc_offset": "+00:00",
                "dst_offset": "+00:00"
              },
              {
                "timezone": "Africa/Accra",
                "utc_offset": "+00:00",
                "dst_offset": "+00:00"
              },
              {
                "timezone": "Africa/Addis_Ababa",
                "utc_offset": "+03:00",
                "dst_offset": "+03:00"
              },
              {
                "timezone": "Africa/Algiers",
                "utc_offset": "+01:00",
                "dst_offset": "+01:00"
              },
              {
                "timezone": "Africa/Asmara",
                "utc_offset": "+03:00",
                "dst_offset": "+03:00"
              },
              {
                "timezone": "Africa/Bamako",
                "utc_offset": "+00:00",
                "dst_offset": "+00:00"
              }
            ]
          },
          {
            "continent": "UTC",
            "timezones": [
              {
                "timezone": "UTC",
                "utc_offset": "+00:00",
                "dst_offset": "+00:00"
              }
            ]
          }
        ]
      }
    }
  },
  "required": [
    "continents"
  ]
}

当前Schema用enum限定每个大洲对象的完整结构，这意味着输入的大洲对象必须和enum里的某一项完全匹配。对于Africa来说，enum里的项包含了所有6个时区的数组，所以当输入只包含单个时区时，整个对象和enum项不匹配，导致验证失败。而UTC的enum项只有一个时区，输入和它完全匹配时就能通过验证。

要实现“选择某大洲下任意数量（至少1个）的合法时区”的需求，需要把enum替换为oneOf，针对每个大洲单独定义规则：

• 指定continent字段的固定值（比如"Africa"或"UTC"）
• 限定timezones数组里的每个时区必须是该大洲允许的选项之一
• 确保timezones数组至少有一个元素

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "Continents Timezones",
  "type": "object",
  "properties": {
    "continents": {
      "type": "array",
      "items": {
        "type": "object",
        "required": ["continent", "timezones"],
        "oneOf": [
          {
            "properties": {
              "continent": {
                "const": "Africa"
              },
              "timezones": {
                "type": "array",
                "minItems": 1,
                "items": {
                  "type": "object",
                  "required": ["timezone", "utc_offset", "dst_offset"],
                  "properties": {
                    "timezone": {
                      "enum": [
                        "Africa/Abidjan",
                        "Africa/Accra",
                        "Africa/Addis_Ababa",
                        "Africa/Algiers",
                        "Africa/Asmara",
                        "Africa/Bamako"
                      ]
                    },
                    "utc_offset": {
                      "type": "string"
                    },
                    "dst_offset": {
                      "type": "string"
                    }
                  },
                  "additionalProperties": false
                }
              }
            },
            "additionalProperties": false
          },
          {
            "properties": {
              "continent": {
                "const": "UTC"
              },
              "timezones": {
                "type": "array",
                "minItems": 1,
                "items": {
                  "type": "object",
                  "required": ["timezone", "utc_offset", "dst_offset"],
                  "properties": {
                    "timezone": {
                      "const": "UTC"
                    },
                    "utc_offset": {
                      "const": "+00:00"
                    },
                    "dst_offset": {
                      "const": "+00:00"
                    }
                  },
                  "additionalProperties": false
                }
              }
            },
            "additionalProperties": false
          }
        ]
      }
    }
  },
  "required": ["continents"]
}

如果需要确保时区和对应的UTC/DST偏移量完全匹配，避免用户输入错误的偏移值，可以为每个时区单独定义oneOf规则，确保时区和偏移量一一对应：

// 替换Africa的timezones.items部分
"items": {
  "type": "object",
  "required": ["timezone", "utc_offset", "dst_offset"],
  "oneOf": [
    {
      "properties": {
        "timezone": {"const": "Africa/Abidjan"},
        "utc_offset": {"const": "+00:00"},
        "dst_offset": {"const": "+00:00"}
      },
      "additionalProperties": false
    },
    {
      "properties": {
        "timezone": {"const": "Africa/Accra"},
        "utc_offset": {"const": "+00:00"},
        "dst_offset": {"const": "+00:00"}
      },
      "additionalProperties": false
    },
    // 其他Africa时区依次类推
  ]
}

内容的提问来源于stack exchange，提问作者klausk