Fastify中JWT装饰器异步函数类型不匹配报错求助

问题描述 #

我正在使用Fastify框架，尝试添加两种JWT认证方式，使用的代码如下：

import fp from 'fastify-plugin';
import { FastifyInstance, FastifyRequest } from 'fastify';
import '@fastify/jwt';

declare module '@fastify/jwt' {
    interface FastifyJWT {
        payload: { id: number };
        user: {
            id: number;
            fullName: string;
            email: number;
            phoneNumber: number;
            role: string;
            blocked: false;
            userMethod: string;
            verified: boolean;
            createdAt: string;
        };
    }
}

const jwtPlugin = async (instance: FastifyInstance) => {
    instance.register(import('@fastify/jwt'), {
        secret: instance.configs.jwt.secret,
    });

    instance.decorate('authenticate', async (request: FastifyRequest) => {
        try {
            await request.jwtVerify();
        } catch (error) {
            throw instance.httpErrors.unauthorized();
        }
    });
    // check if user is authenticated without throwing error (used for check user location)
    instance.decorate('isAuthenticated', async (request: FastifyRequest) => {
        try {
            await request.jwtVerify();
        } catch (error) {
            return;
        }
    });
};

export default fp(jwtPlugin, {
    name: 'jwt-plugin',
});

但在instance.decorate的async (request: FastifyRequest) => {}异步函数处出现如下TypeScript错误：

No overload matches this call.
  Overload 1 of 4, '(property: string | symbol, value: null): FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault>', gave the following error.
    Argument of type '(request: FastifyRequest) => Promise<void>' is not assignable to parameter of type 'null'.
  Overload 2 of 4, '(property: "isAuthenticated", value: GetterSetter<FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault>, (this: FastifyInstance<...>) => void>, dependencies?: string[] | undefined): FastifyInstance<...>', gave the following error.
    Argument of type '(request: FastifyRequest) => Promise<void>' is not assignable to type 'GetterSetter<FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault>, (this: FastifyInstance<...>) => void>'.
      Type '(request: FastifyRequest) => Promise<void>' is not assignable to type '(this: FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault>) => void'.
        Target signature provides too few arguments. Expected 1 or more, but got 0.ts(2769)

该代码是从之前参与的项目中复制的，当时可正常运行，请问该如何修复这个错误？

修复方案 #

错误原因 #

你误用了Fastify的装饰器方法：decorate是用来给Fastify实例本身添加属性/方法的，而你要实现的是给**请求对象（FastifyRequest）**添加认证方法，应该用decorateRequest。同时新版本Fastify的TypeScript类型定义更严格，需要显式扩展FastifyRequest的类型声明。

具体修复步骤 #

1. 替换装饰器方法：把instance.decorate替换为instance.decorateRequest，因为这两个认证方法是要绑定到每个请求对象上的。
2. 扩展FastifyRequest类型：添加类型声明，让TypeScript识别新增的请求方法。
3. 修正字段类型错误：原代码中user接口的email和phoneNumber被定义为number，这不符合实际场景，应该改为string；blocked写死为false，改为boolean更合理。

修复后的完整代码 #

import fp from 'fastify-plugin';
import { FastifyInstance, FastifyRequest } from 'fastify';
import '@fastify/jwt';

declare module '@fastify/jwt' {
    interface FastifyJWT {
        payload: { id: number };
        user: {
            id: number;
            fullName: string;
            email: string; // 修正为string类型
            phoneNumber: string; // 修正为string类型
            role: string;
            blocked: boolean; // 改为boolean类型支持两种状态
            userMethod: string;
            verified: boolean;
            createdAt: string;
        };
    }
}

// 扩展FastifyRequest类型，声明新增的方法
declare module 'fastify' {
    interface FastifyRequest {
        authenticate: () => Promise<void>;
        isAuthenticated: () => Promise<void>;
    }
}

const jwtPlugin = async (instance: FastifyInstance) => {
    instance.register(import('@fastify/jwt'), {
        secret: instance.configs.jwt.secret,
    });

    // 使用decorateRequest给请求对象添加方法，用function确保this指向当前请求
    instance.decorateRequest('authenticate', async function (this: FastifyRequest) {
        try {
            await this.jwtVerify();
        } catch (error) {
            throw instance.httpErrors.unauthorized();
        }
    });

    // check if user is authenticated without throwing error (used for check user location)
    instance.decorateRequest('isAuthenticated', async function (this: FastifyRequest) {
        try {
            await this.jwtVerify();
        } catch (error) {
            return;
        }
    });
};

export default fp(jwtPlugin, {
    name: 'jwt-plugin',
});

额外说明 #

• 使用普通函数而非箭头函数，确保this能正确指向当前请求对象，避免jwtVerify调用时的上下文问题。
• 调整后的字段类型更贴合实际业务场景，避免后续使用时出现类型不匹配的问题。

内容的提问来源于stack exchange，提问作者user10596155