Fastify集成@fastify/swagger报错：fastify.swagger is not a function

启动Fastify应用时出现如下错误：

fastify_app@1.0.0 start D:\dev\fastify_app
 node app.js

{"level":30,"time":1666146720089,"pid":13484,"hostname":"Dell","msg":"Server listening at http://127.0.0.1:3000"}
{"level":30,"time":1666146720113,"pid":13484,"hostname":"Dell","msg":"Server listening at http://[::1]:3000"}
D:\dev\fastify_app\app.js:15
      fastify.swagger()
              ^

TypeError: fastify.swagger is not a function
    at D:\dev\fastify_app\app.js:15:15
    at D:\dev\fastify_app\node_modules\fastify\lib\server.js:67:11
    at Object.cb (D:\dev\fastify_app\node_modules\fastify\lib\server.js:128:15)
    at Server.wrap (D:\dev\fastify_app\node_modules\fastify\lib\server.js:166:21)
    at Object.onceWrapper (events.js:519:28)
    at Server.emit (events.js:400:28)
    at emitListeningNT (net.js:1365:10)
    at processTicksAndRejections (internal/process/task_queues.js:81:21)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! fastify_app@1.0.0 start: `node app.js`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the fastify_app@1.0.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Users\Dell\AppData\Roaming\npm-cache\_logs\2022-10-19T02_32_00_228Z-debug.log

问题原因 #

1. Swagger插件未关联主Fastify实例：你的swagger.js中创建了独立的Fastify实例并注册Swagger，没有将插件绑定到应用的主实例上，导致主实例不存在swagger()方法。
2. 多余的手动调用：@fastify/swagger注册后会自动生成文档路由，不需要在listen回调中手动调用fastify.swagger()。

修正方案 #

修改swagger.js

改为导出符合Fastify插件规范的函数，接收主实例并完成Swagger注册：

module.exports = async function (fastify, opts) {
  await fastify.register(require("@fastify/swagger"), {
    routePrefix: "/docs",
    exposeRoute: true,
    swagger: {
      info: {
        title: "Fastify API",
        description: "Building a blazing fast REST API with Node.js, MongoDB, Fastify and Swagger",
        version: "1.0.0",
      },
      externalDocs: {
        url: "https://swagger.io",
        description: "Find more info here",
      },
      host: "localhost:3000",
      schemes: ["http"],
      consumes: ["application/json"],
      produces: ["application/json"],
    },
  });
};

修改app.js

在主实例中注册Swagger插件，同时移除不必要的fastify.swagger()调用：

const fastify = require("fastify")({logger:true});
require("dotenv").config();
const PORT = process.env.PORT;

// 先注册Swagger插件
fastify.register(require('./swagger'));
fastify.register(require("./app/Routes/users.route"));

fastify.get("/", (req, res) => {
  res.send("Hello world");
});

const start = async () => {
  try {
    await fastify.listen({ port: PORT });
    console.log(`server is listening on port ${PORT}`);
  } catch (error) {
    console.log(error);
    process.exit(1);
  }
};
start();

验证 #

启动应用后，访问http://localhost:3000/docs即可查看Swagger文档界面，TypeError错误会消失。

内容的提问来源于stack exchange，提问作者Vamsi