Mongoose findByIdAndUpdate更新嵌套字段时未传字段置空问题

问题根因 #

• 现有代码中$set直接传入嵌套对象整体结构，MongoDB 不会对嵌套对象执行深度合并，会直接将对应字段路径整体替换为传入值
• 接口参数解构时，本次请求未传递的字段值为undefined，整体写入时会覆盖原有字段值，最终表现为未传字段被置为null
• 额外写法问题：findByIdAndUpdate 第一个参数原生支持直接传入文档_id，不需要包装为{_id: xxx}的查询对象；Mongoose 6及以上版本已默认移除useFindAndModify配置，无需手动声明。

修复方案 #

方案1：使用点语法指定更新路径（生产环境推荐） #

通过父字段.子字段的点语法明确声明需要更新的字段路径，$set只会更新明确指定的路径，不会影响同层级其他原有字段。同时需要动态判断传入字段是否存在，避免将undefined写入数据库。
修复后的完整代码：

async updatePaymentMethod({
  name,
  method,
  inheritToSubsidiaries,
  invoiceEmail,
  requireProjectId,
  billing_address: {
    city,
    country,
    organization_name,
    postal_code,
    references: { attn, co, reference } = {},
    region,
    street_address,
  } = {},
} = {}) {
  if (method == "INVOICE") {
    try {
      const { company } = await this.context.dataSources.user.getCompany();
      const updatePayload = {};

      // 组装顶层待更新字段
      if (name !== undefined) updatePayload.name = name;

      // 组装paymentMethod嵌套字段
      if (method !== undefined) updatePayload["paymentMethod.method"] = method;
      if (invoiceEmail !== undefined) updatePayload["paymentMethod.invoiceEmail"] = invoiceEmail;
      if (inheritToSubsidiaries !== undefined) updatePayload["paymentMethod.inheritToSubsidiaries"] = inheritToSubsidiaries;
      if (requireProjectId !== undefined) updatePayload["paymentMethod.requireProjectId"] = requireProjectId;

      // 组装billing_address嵌套字段
      if (city !== undefined) updatePayload["billing_address.city"] = city;
      if (country !== undefined) updatePayload["billing_address.country"] = country;
      if (organization_name !== undefined) updatePayload["billing_address.organization_name"] = organization_name;
      if (postal_code !== undefined) updatePayload["billing_address.postal_code"] = postal_code;
      if (region !== undefined) updatePayload["billing_address.region"] = region;
      if (street_address !== undefined) updatePayload["billing_address.street_address"] = street_address;

      // 组装最深层references嵌套字段
      if (attn !== undefined) updatePayload["billing_address.references.attn"] = attn;
      if (co !== undefined) updatePayload["billing_address.references.co"] = co;
      if (reference !== undefined) updatePayload["billing_address.references.reference"] = reference;

      const updatedCompany = await Company.findByIdAndUpdate(
        company._id,
        { $set: updatePayload },
        { new: true }
      );
      console.log(updatedCompany);
      return {
        success: true,
        message: "ok",
      };
    } catch (e) {
      return {
        success: false,
        message: "failed",
        e,
      };
    }
  }
}

方案2：Schema配置嵌套对象自动合并（非必要不推荐） #

如果不想手动拼接更新路径，可以在定义Schema时给嵌套对象字段添加merge: true配置，Mongoose会在更新时自动合并嵌套对象。但该配置为全局生效，会影响该Model所有更新操作，容易出现非预期的写入行为。
配置示例：

const companySchema = new mongoose.Schema({
  // 其余字段定义
  billing_address: {
    type: Object,
    merge: true
  },
  paymentMethod: {
    type: Object,
    merge: true
  }
})

问题复现截图 #

• 更新前文档状态：
  
• 更新后异常状态：
  

内容的提问来源于stack exchange，提问作者rakesh laishetty