Fastify Schema读取嵌套对象报错：无法读取null的name属性

问题场景 #

使用的Fastify Schema如下：

{"response": {"200": {"type": "object","properties": {"data": {"type": "array","items": {"type": "object","properties": {"id": {"type": "string"},"created_at": {"type": "string"},"modified_at": {"type": "string"},"title": {"type": "string","example": "unit #323","description": "the org unit's title"},"parent": {"type": "string","description": "the parent org unit","nullable": true,"example": null},"manager": {"type": "object","properties": {"code": {"type": "string","example": "code#538","description": "employer code"},"name": {"type": "string","example": "John"},"status": {"type": "string","nullable": true,"enum": ["active","inactive"]},"org_unit": {"type": "string","nullable": true}}}}},"next": {"type": "string"},"prev": {"type": "string"}}}},"querystring": {"filter": {"type": "string","description": "a json decoded string of fields to be filtered, or a sql where statement with query.values provided","example": {"title": "value","parent": "value","manager": "value"}}}}

Schema核心结构：

{
  id,
  title,
  manager: {id, name, code, ....}
}

预期响应数据结构：

[
 {id, manager: {id, name, ...}}
]

运行时出现如下错误：

Cannot read properties of null (reading 'name')
    at anonymous3 (eval at build (node_modules/fast-json-stringify/index.js:175:23),

移除Schema中的manager字段后，错误消失。

问题原因 #

错误指向访问null对象的name属性，说明实际返回的响应数据中，manager字段存在为null的情况，但当前Schema里的manager字段仅定义了type: "object"，未设置nullable: true。Fastify依赖的fast-json-stringify会基于Schema生成序列化逻辑，默认认为manager一定是对象，当实际数据为null时，就会触发读取null属性的报错。

解决方案 #

给Schema中的manager字段添加nullable: true配置，使其匹配实际数据中可能为null的场景：

修改后的manager字段Schema片段：

"manager": {
  "type": "object",
  "nullable": true,
  "properties": {
    "code": {"type": "string","example": "code#538","description": "employer code"},
    "name": {"type": "string","example": "John"},
    "status": {"type": "string","nullable": true,"enum": ["active","inactive"]},
    "org_unit": {"type": "string","nullable": true}
  }
}

这样fast-json-stringify在序列化时会先判断manager是否为null，为null时不会尝试读取其内部属性，避免报错。

内容的提问来源于stack exchange，提问作者Sherif eldeeb