FastifyのTypeScriptとディレクトリ構成 — 実務で育てやすい形にする

src/
├── app.ts
├── server.ts
├── routes/
│   └── todos.ts
├── services/
│   └── todoService.ts
└── repositories/
    └── todoRepository.ts

npm install fastify
npm install -D typescript @types/node tsx

{
  "type": "module",
  "scripts": {
    "dev": "tsx watch src/server.ts",
    "start": "tsx src/server.ts",
    "test": "node --test --import tsx"
  }
}

{
  "compilerOptions": {
    "target": "ES2022",
    "module": "NodeNext",
    "moduleResolution": "NodeNext",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true
  }
}

type CreateTodoBody = {
  title: string;
};
 
fastify.post<{ Body: CreateTodoBody }>('/todos', async (request, reply) => {
  const title = request.body.title;
  return reply.code(201).send({ title, completed: false });
});

type CreateTodoBody = {
  title: string;
};
 
const createTodoBodySchema = {
  type: 'object',
  required: ['title'],
  additionalProperties: false,
  properties: {
    title: { type: 'string', minLength: 1, maxLength: 100 },
  },
} as const;