Fastify中request.query无法自动推断Schema类型的问题

问题描述 #

我是Fastify结合TypeScript的新手，在代码中执行const {name} = req.query时出现类型错误：Property 'name' does not exist on type 'unknown'.ts(2339)。疑惑定义的Schema是否应该自动为name提供类型推断，还是需要手动为req变量添加类型？

相关代码与配置 #

路由代码

import { Type } from '@sinclair/typebox';
import { FastifyPluginAsyncTypebox } from '@fastify/type-provider-typebox'
import { FastifyInstance } from 'fastify';

const plugin: FastifyPluginAsyncTypebox = async function(fastify: FastifyInstance) {
  fastify.get('/', {
    schema: {
      querystring: Type.Object({
        name: Type.String({ default: 'world' })
      }),
      response: {
        200: Type.Object({
          hello: Type.String()
        })
      }
    }
  }, (req) => {
    const { name } = req.query;
    return { hello: name };
  });

  fastify.post('/', {
    schema: {
      body: Type.Object({
        name: Type.String()
      }),
      response: {
        200: Type.Object({
          hello: Type.String()
        })
      }
    }
  }, async (request) => {
    const { name } = request.body;
    return { hello: name || 'world' };
  });
}

export default plugin;

tsconfig.json

{
  "extends": "fastify-tsconfig",
  "compilerOptions": {
    "outDir": "build",
    "target": "es2018",
    "lib": ["es2018"]
  }
}

package.json

{
  "name": "fastify",
  "version": "1.0.0",
  "main": "index.js",
  "scripts": {
    "build": "tsc -p tsconfig.json",
    "start": "node index.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "description": "",
  "dependencies": {
    "fastify": "^4.27.0"
  },
  "devDependencies": {
    "@fastify/autoload": "^5.8.2",
    "@fastify/swagger": "^8.14.0",
    "@fastify/swagger-ui": "^3.0.0",
    "@fastify/type-provider-typebox": "^4.0.0",
    "@sinclair/typebox": "^0.32.30",
    "@tsconfig/recommended": "^1.0.6",
    "@types/node": "^20.12.11",
    "fastify-tsconfig": "^1.0.0",
    "typescript": "^5.4.5"
  }
}

原因分析与解决方案 #

原因 #

你导入的FastifyInstance来自fastify核心包，这个默认实例没有集成TypeBox的类型解析能力，导致req.query和req.body的类型被推断为unknown，自然无法识别Schema中定义的name属性。

解决步骤 #

只需要修改FastifyInstance的导入来源，从@fastify/type-provider-typebox包中导入该类型，Fastify就会自动根据你定义的Schema为请求对象生成精确的类型，无需手动为req添加类型。

修改后的代码

import { Type } from '@sinclair/typebox';
// 从type-provider-typebox同时导入FastifyPluginAsyncTypebox和FastifyInstance
import { FastifyPluginAsyncTypebox, FastifyInstance } from '@fastify/type-provider-typebox'

const plugin: FastifyPluginAsyncTypebox = async function(fastify: FastifyInstance) {
  fastify.get('/', {
    schema: {
      querystring: Type.Object({
        name: Type.String({ default: 'world' })
      }),
      response: {
        200: Type.Object({
          hello: Type.String()
        })
      }
    }
  }, (req) => {
    const { name } = req.query; // 类型推断正常，无报错
    return { hello: name };
  });

  fastify.post('/', {
    schema: {
      body: Type.Object({
        name: Type.String()
      }),
      response: {
        200: Type.Object({
          hello: Type.String()
        })
      }
    }
  }, async (request) => {
    const { name } = request.body; // 类型推断正常
    return { hello: name || 'world' };
  });
}

export default plugin;

补充说明 #

当前你的tsconfig.json和package.json配置版本兼容，无需额外调整。修改导入来源后，TypeScript就能通过Schema自动推断请求参数的类型，实现类型安全的路由处理。

内容的提问来源于stack exchange，提问作者cornstar94