Aspidaに感動しちゃった件について

# はじめに
突然ですが。Aspidaって知ってますか？？
僕は、知りませんでした。。
仕事先の先輩から教えてもらい感動しちゃったので、記事にしちゃいました。w

# Aspidaとは？
![aspida.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/563635/328cbee8-1ee9-470a-44b9-84cc141ee160.png)

* TypeScriptフレンドリーなHTTPクライアントの為のライブラリです。
* [GitHub: Aspida](https://github.com/aspida/aspida)

## Aspidaの利点
* HTTPクライアントである[axios]、[ky]、[fetch]を使用したAPI リクエスト/レスポンスに型を付与できる点
* リクエストを文字列ではなく、プロパティ経由で行えるようになる点

# 試してみる
今回は、Swaggerをaspidaの型定義ファイルに一発変換してみたいと思います。
=> めっちゃ感動しました。。

また今回は、[Swagger Petstore](https://petstore.swagger.io/)を使用しました。
## インストール
HTTPクライアントである[axios][ky][fetch]から選択する。
今回はaxiosを使っていきます。

```
npm init -y
npm install @aspida/axios axios
```

## apiディレクトリを作成する

```
mkdir api
```

## package.jsonに型定義ファイルをビルドする設定を入れる

```package.json
{
  "scripts": {
    "api:build": "aspida"
  }
}
```

## aspidaの設定ファイルを作成する

```aspida.config.js
module.exports = {
    input: "api",
    outputEachDir: true,
    openapi: { inputFile: "https://petstore.swagger.io/v2/swagger.json" }
};
```

# 型定義の生成
```
npx openapi2aspida
```

## 実行結果

```@types.ts
/* eslint-disable */
export type ApiResponse = {
  code: number
  type: string
  message: string
}

export type Category = {
  id: number
  name: string
}

export type Pet = {
  id?: number
  category?: Category
  name: string
  photoUrls: string[]
  tags?: Tag[]
  status?: 'available' | 'pending' | 'sold'
}

export type Tag = {
  id: number
  name: string
}

export type Order = {
  id: number
  petId: number
  quantity: number
  shipDate: string
  status: 'placed' | 'approved' | 'delivered'
  complete: boolean
}

export type User = {
  id: number
  username: string
  firstName: string
  lastName: string
  email: string
  password: string
  phone: string
  userStatus: number
}

```

```$api.ts
/* eslint-disable */
import { AspidaClient, BasicHeaders, dataToURLString } from 'aspida'
import { Methods as Methods0 } from './pet'
import { Methods as Methods1 } from './pet/_petId@number'
import { Methods as Methods2 } from './pet/_petId@number/uploadImage'
import { Methods as Methods3 } from './pet/findByStatus'
import { Methods as Methods4 } from './store/inventory'
import { Methods as Methods5 } from './store/order'
import { Methods as Methods6 } from './store/order/_orderId@number'
import { Methods as Methods7 } from './user'
import { Methods as Methods8 } from './user/_username@string'
import { Methods as Methods9 } from './user/createWithArray'
import { Methods as Methods10 } from './user/createWithList'
import { Methods as Methods11 } from './user/login'

const api = <T>({ baseURL, fetch }: AspidaClient<T>) => {
  const prefix = (baseURL === undefined ? 'https://petstore.swagger.io/v2' : baseURL).replace(/\/$/, '')
  const PATH0 = '/pet'
  const PATH1 = '/uploadImage'
  const PATH2 = '/pet/findByStatus'
  const PATH3 = '/store/inventory'
  const PATH4 = '/store/order'
  const PATH5 = '/user'
  const PATH6 = '/user/createWithArray'
  const PATH7 = '/user/createWithList'
  const PATH8 = '/user/login'
  const GET = 'GET'
  const POST = 'POST'
  const PUT = 'PUT'
  const DELETE = 'DELETE'

  return {
    pet: {
      _petId: (val1: number) => {
        const prefix1 = `${PATH0}/${val1}`

        return {
          uploadImage: {
            post: (option: { body: Methods2['post']['reqBody'], config?: T }) =>
              fetch<Methods2['post']['resBody'], BasicHeaders, Methods2['post']['status']>(prefix, `${prefix1}${PATH1}`, POST, option, 'FormData').json(),
            $post: (option: { body: Methods2['post']['reqBody'], config?: T }) =>
              fetch<Methods2['post']['resBody'], BasicHeaders, Methods2['post']['status']>(prefix, `${prefix1}${PATH1}`, POST, option, 'FormData').json().then(r => r.body),
            $path: () => `${prefix}${prefix1}${PATH1}`
          },
          get: (option?: { config?: T }) =>
            fetch<Methods1['get']['resBody'], BasicHeaders, Methods1['get']['status']>(prefix, prefix1, GET, option).json(),
          $get: (option?: { config?: T }) =>
            fetch<Methods1['get']['resBody'], BasicHeaders, Methods1['get']['status']>(prefix, prefix1, GET, option).json().then(r => r.body),
          post: (option: { body: Methods1['post']['reqBody'], config?: T }) =>
            fetch(prefix, prefix1, POST, option, 'URLSearchParams').send(),
          $post: (option: { body: Methods1['post']['reqBody'], config?: T }) =>
            fetch(prefix, prefix1, POST, option, 'URLSearchParams').send().then(r => r.body),
          delete: (option?: { headers?: Methods1['delete']['reqHeaders'], config?: T }) =>
            fetch(prefix, prefix1, DELETE, option).send(),
          $delete: (option?: { headers?: Methods1['delete']['reqHeaders'], config?: T }) =>
            fetch(prefix, prefix1, DELETE, option).send().then(r => r.body),
          $path: () => `${prefix}${prefix1}`
        }
      },
      findByStatus: {
        get: (option: { query: Methods3['get']['query'], config?: T }) =>
          fetch<Methods3['get']['resBody'], BasicHeaders, Methods3['get']['status']>(prefix, PATH2, GET, option).json(),
        $get: (option: { query: Methods3['get']['query'], config?: T }) =>
          fetch<Methods3['get']['resBody'], BasicHeaders, Methods3['get']['status']>(prefix, PATH2, GET, option).json().then(r => r.body),
        $path: (option?: { method?: 'get'; query: Methods3['get']['query'] }) =>
          `${prefix}${PATH2}${option && option.query ? `?${dataToURLString(option.query)}` : ''}`
      },
      post: (option: { body: Methods0['post']['reqBody'], config?: T }) =>
        fetch(prefix, PATH0, POST, option).send(),
      $post: (option: { body: Methods0['post']['reqBody'], config?: T }) =>
        fetch(prefix, PATH0, POST, option).send().then(r => r.body),
      put: (option: { body: Methods0['put']['reqBody'], config?: T }) =>
        fetch(prefix, PATH0, PUT, option).send(),
      $put: (option: { body: Methods0['put']['reqBody'], config?: T }) =>
        fetch(prefix, PATH0, PUT, option).send().then(r => r.body),
      $path: () => `${prefix}${PATH0}`
    },
    store: {
      inventory: {
        get: (option?: { config?: T }) =>
          fetch<Methods4['get']['resBody'], BasicHeaders, Methods4['get']['status']>(prefix, PATH3, GET, option).json(),
        $get: (option?: { config?: T }) =>
          fetch<Methods4['get']['resBody'], BasicHeaders, Methods4['get']['status']>(prefix, PATH3, GET, option).json().then(r => r.body),
        $path: () => `${prefix}${PATH3}`
      },
      order: {
        _orderId: (val2: number) => {
          const prefix2 = `${PATH4}/${val2}`

          return {
            get: (option?: { config?: T }) =>
              fetch<Methods6['get']['resBody'], BasicHeaders, Methods6['get']['status']>(prefix, prefix2, GET, option).json(),
            $get: (option?: { config?: T }) =>
              fetch<Methods6['get']['resBody'], BasicHeaders, Methods6['get']['status']>(prefix, prefix2, GET, option).json().then(r => r.body),
            delete: (option?: { config?: T }) =>
              fetch(prefix, prefix2, DELETE, option).send(),
            $delete: (option?: { config?: T }) =>
              fetch(prefix, prefix2, DELETE, option).send().then(r => r.body),
            $path: () => `${prefix}${prefix2}`
          }
        },
        post: (option: { body: Methods5['post']['reqBody'], config?: T }) =>
          fetch<Methods5['post']['resBody'], BasicHeaders, Methods5['post']['status']>(prefix, PATH4, POST, option).json(),
        $post: (option: { body: Methods5['post']['reqBody'], config?: T }) =>
          fetch<Methods5['post']['resBody'], BasicHeaders, Methods5['post']['status']>(prefix, PATH4, POST, option).json().then(r => r.body),
        $path: () => `${prefix}${PATH4}`
      }
    },
    user: {
      _username: (val1: string) => {
        const prefix1 = `${PATH5}/${val1}`

        return {
          get: (option?: { config?: T }) =>
            fetch<Methods8['get']['resBody'], BasicHeaders, Methods8['get']['status']>(prefix, prefix1, GET, option).json(),
          $get: (option?: { config?: T }) =>
            fetch<Methods8['get']['resBody'], BasicHeaders, Methods8['get']['status']>(prefix, prefix1, GET, option).json().then(r => r.body),
          put: (option: { body: Methods8['put']['reqBody'], config?: T }) =>
            fetch(prefix, prefix1, PUT, option).send(),
          $put: (option: { body: Methods8['put']['reqBody'], config?: T }) =>
            fetch(prefix, prefix1, PUT, option).send().then(r => r.body),
          delete: (option?: { config?: T }) =>
            fetch(prefix, prefix1, DELETE, option).send(),
          $delete: (option?: { config?: T }) =>
            fetch(prefix, prefix1, DELETE, option).send().then(r => r.body),
          $path: () => `${prefix}${prefix1}`
        }
      },
      createWithArray: {
        post: (option: { body: Methods9['post']['reqBody'], config?: T }) =>
          fetch(prefix, PATH6, POST, option).send(),
        $post: (option: { body: Methods9['post']['reqBody'], config?: T }) =>
          fetch(prefix, PATH6, POST, option).send().then(r => r.body),
        $path: () => `${prefix}${PATH6}`
      },
      createWithList: {
        post: (option: { body: Methods10['post']['reqBody'], config?: T }) =>
          fetch(prefix, PATH7, POST, option).send(),
        $post: (option: { body: Methods10['post']['reqBody'], config?: T }) =>
          fetch(prefix, PATH7, POST, option).send().then(r => r.body),
        $path: () => `${prefix}${PATH7}`
      },
      login: {
        get: (option: { query: Methods11['get']['query'], config?: T }) =>
          fetch<Methods11['get']['resBody'], Methods11['get']['resHeaders'], Methods11['get']['status']>(prefix, PATH8, GET, option).text(),
        $get: (option: { query: Methods11['get']['query'], config?: T }) =>
          fetch<Methods11['get']['resBody'], Methods11['get']['resHeaders'], Methods11['get']['status']>(prefix, PATH8, GET, option).text().then(r => r.body),
        $path: (option?: { method?: 'get'; query: Methods11['get']['query'] }) =>
          `${prefix}${PATH8}${option && option.query ? `?${dataToURLString(option.query)}` : ''}`
      },
      post: (option: { body: Methods7['post']['reqBody'], config?: T }) =>
        fetch(prefix, PATH5, POST, option).send(),
      $post: (option: { body: Methods7['post']['reqBody'], config?: T }) =>
        fetch(prefix, PATH5, POST, option).send().then(r => r.body),
      $path: () => `${prefix}${PATH5}`
    }
  }
}

export type ApiInstance = ReturnType<typeof api>
export default api

```

# おわりに
いやまじ、凄すぎです笑

# 参考

[HTTPリクエストを型安全にする手法とOSS](https://qiita.com/m_mitsuhide/items/68406158d35a14fa0aa2)
[SwaggerをTypeScriptに変換してAPIリクエストで型チェックを有効にする](https://qiita.com/m_mitsuhide/items/9ce4e048749075845655)
https://github.com/aspida/openapi2aspida
https://github.com/aspida/aspida/tree/master/packages/aspida/docs/ja#readme