Fastify使用anyOf进行响应序列化异常问题求助

Fastify默认启用removeAdditional: true的AJV配置，会依据匹配到的JSON Schema过滤未声明的属性。你的data字段通过anyOf定义了三种返回结构，但前两个schema默认允许额外属性（additionalProperties: true），导致返回tempToken结构时，第一个schema也能通过验证（该结构是合法对象，未违反第一个schema的任何约束）。Fastify会使用第一个schema进行序列化，过滤掉不在其properties中的tempToken和multipleChoice字段，最终返回空对象。

给anyOf中的每个schema添加additionalProperties: false，确保每个schema仅匹配自身声明的字段结构；同时可添加required字段增强约束，避免误匹配。

修改后的核心schema示例 #

data: {
  anyOf: [
    {
      type: "object",
      additionalProperties: false,
      required: ["token", "user"],
      properties: {
        token: { type: "string" },
        user: {
          type: "object",
          additionalProperties: false,
          required: ["id", "phoneNumber"],
          properties: {
            id: { type: "number" },
            phoneNumber: { type: "string" },
          },
        },
      },
    },
    {
      type: "object",
      additionalProperties: false,
      required: ["tempToken", "multipleChoice"],
      properties: {
        tempToken: { type: "string" },
        multipleChoice: {
          type: "object",
          additionalProperties: false,
          required: ["usernames", "locationAddresses"],
          properties: {
            usernames: { type: "array", items: { type: "string" } },
            locationAddresses: {
              type: "array",
              items: { type: "string" },
            },
          },
        },
      },
    },
    {
      type: "object",
      additionalProperties: false,
      required: ["token", "user"],
      properties: {
        token: { type: "string" },
        user: {
          type: "object",
          additionalProperties: false,
          required: ["id", "username"],
          properties: {
            id: { type: "number" },
            username: { type: "string" },
          },
        },
      },
    },
  ],
}

补充说明 #

• additionalProperties: false：禁止schema未声明的额外字段，确保每个anyOf项仅匹配自身结构。
• required：明确指定每个结构的必填字段，进一步避免跨schema的误匹配。
• 若需要更严格的排他匹配，可将anyOf替换为oneOf，结合上述配置效果更佳。

内容的提问来源于stack exchange，提问作者Javohir Mirzo Fazliddinov