Fastify Plugins

import Fastify from "fastify";
import fp from "fastify-plugin";
import autoload from "@fastify/autoload";
import { join } from "node:path";
 
const app = Fastify({ logger: true });
 
// Shared decorator (breaks encapsulation intentionally)
await app.register(fp(async (fastify) => {
  fastify.decorate("db", { query: async (sql: string) => [] });
}));
 
// Autoload all plugins in ./plugins and routes in ./routes
await app.register(autoload, { dir: join(import.meta.dirname, "plugins") });
await app.register(autoload, { dir: join(import.meta.dirname, "routes") });
 
await app.listen({ port: 3000 });

// plugins/database.ts
import fp from "fastify-plugin";
 
export default fp(async (fastify) => {
  const pool = { query: async (sql: string) => [{ id: 1 }] };
  fastify.decorate("db", pool);
  fastify.addHook("onClose", async () => {
    // close pool connections
  });
});
 
// routes/users.ts
import { FastifyPluginAsync } from "fastify";
 
const users: FastifyPluginAsync = async (fastify) => {
  fastify.get("/", async () => {
    return fastify.db.query("SELECT * FROM users");
  });
};
 
export default users;
 
// app.ts
import Fastify from "fastify";
import autoload from "@fastify/autoload";
import { join, dirname } from "node:path";
import { fileURLToPath } from "node:url";
 
const __dirname = dirname(fileURLToPath(import.meta.url));
const app = Fastify({ logger: true });
 
await app.register(autoload, { dir: join(__dirname, "plugins") });
await app.register(autoload, { dir: join(__dirname, "routes"), options: { prefix: "/api" } });

import "fastify";
 
declare module "fastify" {
  interface FastifyInstance {
    db: { query: (sql: string) => Promise<unknown[]> };
  }
}