TachiJS

Tachi(太刀) https://en.wikipedia.org/wiki/Tachi

Highly testable dead simple web server written in Typescript

• 🏁 Highly testable. (all props in req and res are injectable so you don't have to mock at all.)
• 🔧 Highly customizable.
• 💉 Simple dependency injection.
• ⚡ async/await request handler. (like Koa without any configurations.)
• 🏭 Based on expressjs. (You can benefit from using this mature library)
• ✅ Built-in request body validator.
• 📐 Written in Typescript.

Why?

Nest.js looks nice. But its learning curve is too stiff.(TBH, I still don't know how to redirect dynamically.) Most of people probably do not need to know how Interceptor, Pipe and other things work. It might be good for some enterprize level projects.

But using raw expressjs is also quite painful. To test express apps, you have to use supertest or chai-http things. If you use them, you will lose debugging and error stack while testing because they send actual http request internally. Otherwise, you have to mock up all params, req, res and next, of RequestHandler of express.js.

To deal with the testing problem, inversify-express-utils could be a solution. But it does not support many decorators. To render with view engine like pug, we need to use res.render method. But the only solution is using @response decorator. It means you have to mock up Response in your test. So technically it is super hard to test routes rendering view engine.

Luckily, TachiJS tackles those problems. If you have other ideas, please create an issue!!

How to use

Install tachijs

npm i tachijs reflect-metadata

Add two compiler options, experimentalDecorators and emitDecoratorMetadata, to tsconfig.json.

{
  "compilerOptions": {
    ...
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    ...
  }
}

Quick start

import tachijs, { controller, httpGet } from 'tachijs'

@controller('/')
class HomeController() {
  // Define when this method should be used.
  @httpGet('/')
  index() {
    return {
      message: 'Hello, world!'
    }
  }
}

// Register `HomeController`
const app = tachijs({
  controllers: [HomeController]
})

// `app` is just an express application instance
app.listen(8000)

Now you can access http://localhost:8000/.

For other http methods, tachijs provides @httpPost, @httpPut, @httpPatch, @httpDelete, @httpOptions, @httpHead and @httpAll.

Configuring express app(Middlewares)

There are lots of ways to implement express middlewares.

Use before and after options

import bodyParser from 'body-parser'
import { ConfigSetter, NotFoundException } from 'tachijs'

const before: ConfigSetter = app => {
  app.use(bodyParser())
}

const after: ConfigSetter = app => {
  app.use('*', (req, res, next) => {
    next(new NotFoundException('Page does not exist.'))
  })

  const errorHandler: ErrorRequestHandler = (error, req, res, next) => {
    const { status = 500, message } = error
    res.status(status).json({
      status,
      message
    })
  }
  app.use(errorHandler)
}

const app = tachijs({
  before,
  after
})

app.listen(8000)

Without before or after options

Identically same to the above example.

import express from 'express'
import bodyParser from 'body-parser'
import { ConfigSetter, NotFoundException } from 'tachijs'

const app = express()
app.use(bodyParser())

tachijs({
  app
})

app.use('*', (req, res, next) => {
  next(new NotFoundException('Page does not exist.'))
})

const errorHandler: ErrorRequestHandler = (error, req, res, next) => {
  const { status = 500, message } = error
  res.status(status).json({
    status,
    message
  })
}
app.use(errorHandler)

app.listen(8000)

Apply middlewares to controllers and methods

Sometimes, you might want to apply middlewares to several methods only.

import { controller, httpGet, ForbiddenException } from 'tachijs'
import cors from 'cors'
import { RequestHandler } from 'express'

const onlyAdmin: RequestHandler = (req, res, next) => {
  if (!req.user.admin) {
    next(new ForbiddenException('Only admin users can access this api'))
    return
  }
  next()
}

// Apply `cors()` to controller. Now all methods will use the middleware.
@controller('/', [cors()])
class HomeController() {
  @httpGet('/')
  index() {
    return {
      message: 'Hello, world!'
    }
  }

  // Apply `onlyAdmin` to `admin` method. This middleware will be applied to this method only.
  @httpGet('/', [onlyAdmin])
  admin() {
    return {
      message: 'Hello, world!'
    }
  }
}

Configure router options

Tachijs will create and register a router for each controller.

So you can provide router options via @controller decorator.

@controller('/:name', [], {
  // Provide mergeParams option to express router.
  mergeParams: true
})
class HomeController {
  @httpGet('/hello')
  // Now routes in the controller can access params.
  index(@reqParams('name') name: string) {
    return `Hello, ${name}`
  }
}

Access req.params, req.query and req.body via decorators

You can access them via @reqParams, @reqQuery and @reqBody. (Don't forget to apply body-parser middleware)

import {
  controller,
  httpGet,
  httpPost,
  reqParams,
  reqQuery,
  reqBody
} from 'tachijs'

@controller('/posts')
class PostController() {
  @httpGet('/:postId')
  // `req.params.postId`
  async show(@reqParams('postId') postId: string) {
    const post = await Post.findById(postId)

    return {
      post
    }
  }

  @httpGet('/search')
  // `req.query.title`
  async search(@reqQuery('title') title: string = '') {
    const posts = await Post.find({
      title
    })

    return {
      posts
    }
  }

  @httpPost('/')
  // `req.body` (`@reqBody` does not accept property keys.)
  async create(@reqBody() body: unknown) {
    const validatedBody = validate(body)
    const post = await Post.create({
      ...validatedBody
    })

    return {
      post
    }
  }
}

We also provide reqHeaders, reqCookies and reqSession for req.headers, req.cookies and req.session. To know more, see our api documentation below.

Body validation

@reqBody supports validation via class-validator.

Please install class-validator package first.

npm install class-validator

import { IsString } from 'class-validator'

class PostDTO {
  @IsString()
  title: string

  @IsString()
  content: string
}


@controller('/posts')
class PostController() {
  @httpPost('/')
  // Tachijs can access `PostDTO` via reflect-metadata.
  async create(@reqBody() body: PostDTO) {
    // `body` is already validated and transformed into an instance of `PostDTO`.
    // So we don't need any extra validation.
    const post = await Post.create({
      ...body
    })

    return {
      post
    }
  }
}

Custom parameter decorators!

If you're using passport, you should want to access user data from req.user. @handlerParam decorator make it possible. The decorator gets a selector which accepts express's req, res and next. So all you need to do is decide what to return from thoes three parameters.

import { controller, httpGet, handlerParam } from 'tachijs'

@controller('/')
class HomeController {
  @httpGet('/')
  async showId(@handlerParam((req, res, next) => req.user) user: any) {
    doSomethingWithUser(user)

    return {
      ...
    }
  }
}

If you want reusable code, please try like the below.

import { controller, httpGet, handlerParam } from 'tachijs'

function reqUser() {
  // You can omit other next params, `res` and `next`, if you don't need for your selector.
  return handlerParam(req => req.user)
}

@controller('/')
class HomeController {
  @httpGet('/')
  async showId(@reqUser() user: any) {
    doSomethingWithUser(user)

    return {
      ...
    }
  }
}

Bind methods of req or res before exposing

You can also pass methods of req or res which are augmented by express module. Some of them might need the context of them. So please bind methods before exposing like the below example.

export function cookieSetter() {
  return handlerParam((req, res) => res.cookie.bind(res))
}

design:paramtype

Moreover, tachijs exposes metadata of parameters to forth argument. So you can make your custom validator for query with class-transformer-validator like below. (req.body is also using this.)

import { controller, httpGet, handlerParam } from 'tachijs'
import { IsString } from 'class-validator'
import { transformAndValidate } from 'class-transformer-validator'

function validatedQuery() {
  return handlerParam((req, res, next, meta) => {
    // meta.paramType is from `design:paramtypes`.
    // It is `Object` if the param type is unknown or any.
    return meta.paramType !== Object
      ? transformAndValidate(meta.paramType, req.query)
      : req.query
  })
}

// Validator class
class SearchQuery {
  @IsString()
  title: string
}

@controller('/')
class PostController {
  @httpGet('/search')
  // Provide the validator class to param type.
  // tachijs can access it via `reflect-metadata`.
  search(@validatedQuery() query: SearchQuery) {
    // Now `query` is type-safe
    // because it has been validated and transformed into an instance of SearchQuery.
    const { title } = query

    return {
      ...
    }
  }
}

To know more, see @handlerParam api documentation below.

Redirection, Rendering via pug and others...

Techinically, you don't have to access res to response data. But, if you want to redirect or render page via pug, you need to access res.redirect or res.render. Sadly, if you do, you have make mockup for res.

But, with tachijs, you can tackle this problem.

import { controller, httpGet, RedirectResult } from 'tachijs'

@controller('/')
class HomeController {
  @httpGet('/redirect')
  redirectToHome() {
    return new RedirectResult('/')
  }
}

Now, you can test your controller like the below example.

describe('HomeController#redirectToHome', () => {
  it('redirects to `/`', async () => {
    // Given
    const controller = new HomeController()

    // When
    const result = controller.redirectToHome()

    // Then
    expect(result).toBeInstanceOf(RedirectResult)
    expect(result).toMatchObject({
      location: '/'
    })
  })
})

There are other results too, EndResult, JSONResult, RenderResult, SendFileResult, SendResult, and SendStatusResult. Please see our api documentation below.

BaseController

If you need to use many types of result, you probably want BaseController. Just import it once, and your controller can instantiate results easily.

import { controller, httpGet, BaseController } from 'tachijs'

@controller('/')
// You have to extend your controller from `BaseController`
class HomeController extends BaseController {
  @httpGet('/redirect')
  redirectToHome() {
    // This is identically same to `return new RedirectResult('/')`
    return this.redirect('/')
  }
}

BaseController has methods for all build-in results, Please see our api documentation below.

BaseController#context

You may want to share some common methods via your own base controller. But, sadly, it is not possible to use decorators to get objects from req or res and services provided by @inject.

To make it possible, we introduce context. Which expose req, res and inject method via context if your controller is extended from BaseController.

interface Context {
  req: express.Request
  res: express.Response
  inject<S>(key: string): S
}

import { BaseController, controller, httpPost } from 'tachijs'

class MyBaseController extends BaseController {
  async getUserConfig() {
    // When unit testing, `context` is not defined.
    if (this.context == null) {
      return new UserConfig()
    }

    const { req, inject } = this.context

    // Now we can get the current user from `req`
    const currentUser = req.user

    // And inject any services from the container.
    const userConfigService = inject<UserConfigService>(
      ServiceTypes.UserConfigService
    )

    return userConfigService.findByUserId(userId)
  }
}

@controller('/')
class HomeController {
  @httpGet('/settings')
  settings() {
    const userConfig = await this.getUserConfig()

    return this.render('settings', {
      userConfig
    })
  }
}

#httpContext, #inject and #injector will be deprecated from v1.0.0. Please use #context

Customize result

If you want to have customized result behavior, you can do it with BaseResult. BaseResult is an abstract class which coerce you to define how to end the route by providing execute method. (Every built-in result is extended from BaseResult.)

Let's see our implementation of RedirectResult.

import express from 'express'
import { BaseResult } from './BaseResult'

export class RedirectResult extends BaseResult {
  constructor(
    public readonly location: string,
    public readonly status?: number
  ) {
    super()
  }

  // tachijs will provide all what you need and execute this method.
  async execute(
    req: express.Request,
    res: express.Response,
    next: express.NextFunction
  ) {
    if (this.status != null) return res.redirect(this.status, this.location)
    return res.redirect(this.location)
  }
}

Dependency injection

To make controllers more testable, tachijs provides dependency injection.

Let's think we have some mailing service, MailerService. While developing or testing, we probably don't want our server to send real e-mail everytime.

import tachijs, {
  controller,
  httpGet,
  httpPost,
  reqBody,
  inject,
  BaseController
} from 'tachijs'

// Create enum for service types
enum ServiceTypes {
  EmailService = 'EmailService',
  NotificationService = 'NotificationService'
}

// Abstract class coerce MailerService must have `sendEmail` method.
abstract class MailerService {
  abstract sendEmail(content: string): Promise<void>
}

// Mockup service for development and testing.
class MockEmailService extends MailerService {
  async sendEmail(content: string) {
    console.log(`Not sending email.... content: ${content}`)
  }
}

class EmailService extends MailerService {
  async sendEmail(content: string) {
    console.log(`Sending email.... content: ${content}`)
  }
}

interface Container {
  [ServiceTypes.EmailService]: typeof MailerService
}

const envIsDev = process.env.NODE_ENV === 'development'

// Swapping container depends on the current environment.
const container: Container = envIsDev
  ? {
      // In development env, don't send real e-mail because we use mockup.
      [ServiceTypes.EmailService]: MockEmailService
    }
  : {
      [ServiceTypes.EmailService]: EmailService
    }

@controller('/')
class HomeController extends BaseController {
  constructor(
    // Inject MailerService. The controller will get the one registered to the current container.
    @inject(ServiceTypes.EmailService) private mailer: MailerService
  ) {
    super()
  }

  @httpGet('/')
  home() {
    return `<form action='/notify' method='post'><input type='text' name='message'><button>Notify</button></form>`
  }

  @httpPost('/email')
  async sendEmail(@reqBody() body: any) {
    await this.mailer.sendEmail(body.message)

    return this.redirect('/')
  }
}

const server = tachijs({
  controllers: [HomeController],
  // Register container
  container
})

So you can test HomeController#sendEmail like the below example.

describe('HomeController#sendEmail', () => {
  it('sends email', async () => {
    // Given
    const spyFn = jest.fn()
    class TestEmailService extends MailerService {
      async sendEmail(content: string): Promise<void> {
        spyFn(content)
      }
    }
    const controller = new HomeController(new TestEmailService())

    // When
    const result = controller.sendEmail('hello')

    // Then
    expect(spyFn).toBeCalledWith('hello')
  })
})

Now we don't have to worry that our controller sending e-mail for each testing.

Furthermore, you can inject other services to your service as long as they exist in the container.

class NotificationService {
  constructor(
    // When NotificationService is instantiated, MailerService will be instantiated also by tachijs.
    @inject(ServiceTypes.EmailService) private mailer: MailerService
  ) {}

  async notifyWelcome() {
    await this.mailer.sendEmail('Welcome!')
  }
}

DI without tachijs

When some testing or just writing scripts using services, you might want to use DI without tachijs function. So we exposed Injector class which is used by tachijs.

enum ServiceTypes {
  NameService = 'NameService',
  MyService = 'MyService'
}
class NameService {
  getName() {
    return 'Test'
  }
}
class MyService {
  constructor(
    @inject(ServiceTypes.NameService) private nameService: NameService
  ) {}

  sayHello() {
    return `Hello, ${this.nameService.getName()}`
  }
}
const container = {
  [ServiceTypes.NameService]: NameService,
  [ServiceTypes.MyService]: MyService
}

// Create injector
const injector = new Injector(container)

// Instantiate by a key
const myService = injector.inject<MyService>(ServiceTypes.MyService)
// Instantiate by a constructor
const myService = injector.instantiate(MyService)

Bad practices

Please check this section too to keep your controllers testable.

Execute res.send or next inside of controllers or @handlerParam

Please don't do that. It just make your controller untestable. If you want some special behaviors after your methods are executed, please try to implement them with BaseResult.

Do

class HelloResult extends BaseResult {
  async execute(
    req: express.Request,
    res: express.Response,
    next: express.NextFunction
  ) {
    res.send('Hello')
  }
}

class HomePageController extends BaseController {
  @httpGet('/')
  index() {
    // Now we can test it by just checking the method returns an instance of `HelloResult`.
    return new HelloResult()
  }
}

Don't

class HomePageController {
  @httpGet('/')
  index(@handlerParam((req, res) => res) res: expressResponse) {
    // We have to make mock-up for express.Response to test
    res.send('Hello')
  }
}

Access BaseController#context in your descendant controllers

It is designed to be used inside of your base controller to make unit testing easy.

Do

class MyBaseController extends BaseController {
  doSomethingWithContext() {
    if (this.context == null) {
      // on unit testing
      return
    }
    // on live
  }
}

Don't

class HomePageController extends MyBaseController {
  @httpGet('/')
  index() {
    // We have to make mock-up everything to test
    this.context!.req....
  }
}

APIs

tachijs(options: TachiJSOptions): express.Application

Create and configure an express app.

TachiJSOptions

interface TachiJSOptions<C = {}> {
  app?: express.Application
  before?: ConfigSetter
  after?: ConfigSetter
  controllers?: any[]
  container?: C
}

type ConfigSetter = (app: express.Application) => void

• app Optional. If you provide this option, tachijs will use it rather than creating new one.
• before Optional. You can configure express app before registering controllers for applying middlewares.
• after Optional. You can configure express app before registering controllers for error handling.
• controllers Optional. Array of controller classes.
• container Optional. A place for registered services. If you want to use DI, you have to register services to here first.

@controller(path: string, middlewares: RequestHandler[] = [], routerOptions: RouterOptions = {})

It marks class as a controller.

• path Target path.
• middlewares Optional. Array of middlewares.
• routerOptions Optional. Express router options.

@httpMethod(method: string, path: string, middlewares: RequestHandler[] = [])

It marks method as a request handler.

• method Target http methods, 'get', 'post', 'put', 'patch', 'delete', 'options', 'head' or 'all' are available. ('all' means any methods.)
• path Target path.
• middlewares Optional. Array of middlewares.

tachijs also provides shortcuts for @httpMethod.

• @httpGet(path: string, middlewares: RequestHandler[] = [])
• @httpPost(path: string, middlewares: RequestHandler[] = [])
• @httpPut(path: string, middlewares: RequestHandler[] = [])
• @httpPatch(path: string, middlewares: RequestHandler[] = [])
• @httpDelete(path: string, middlewares: RequestHandler[] = [])
• @httpOptions(path: string, middlewares: RequestHandler[] = [])
• @httpHead(path: string, middlewares: RequestHandler[] = [])
• @httpAll(path: string, middlewares: RequestHandler[] = [])

@handlerParam<T>(selector: HandlerParamSelector<T>)

• selector selects a property from req, res, next or even our meta

export type HandlerParamSelector<T> = (
  req: express.Request,
  res: express.Response,
  next: express.NextFunction,
  meta: HandlerParamMeta<T>
) => T

interface HandlerParamMeta<T> {
  index: number
  selector: HandlerParamSelector<T>
  paramType: any
}

• index Number index of the parameter.
• selector Its selector.
• paramType metadata from design:paramtypes.

@reqBody(validator?: any)

Inject req.body.

• validator Optional. A class with decorators of class-validator. tachijs will validate req.body with it and transform req.body into the validator class. If validator is not given but the parameter has a class validator as its param type, tachijs will use it via reflect-metadata.

import { controller, httpPost, reqBody } from 'tachijs'

@controller('/post')
class PostController {
  @httpPost('/')
  // Identically same to `create(@reqBody(PostDTO) post: PostDTO)`
  create(@reqBody() post: PostDTO) {
    ...
  }
}

@reqParams(paramName?: string)

Inject req.params or its property.

• paramName If it is given, req.params[paramName] will be injected.

@reqQuery(paramName?: string)

Inject req.query or its property.

• paramName If it is given, req.query[paramName] will be injected.

@reqHeaders(paramName?: string)

Inject req.headers or its property.

• paramName If it is given, req.headers[paramName] will be injected.

@reqCookies(paramName?: string)

Inject req.cookies or its property.

• paramName If it is given, req.cookies[paramName] will be injected.

@reqSignedCookies(paramName?: string)

Inject req.signedCookies or its property.

• paramName If it is given, req.signedCookies[paramName] will be injected.

@cookieSetter()

Inject res.cookie method to set cookie.

@cookieClearer()

Inject res.clearCookie method to clear cookie.

@reqSession(paramName?: string)

Inject req.session.

BaseController

A base for controller which have lots of helper methods for returning built-in results. Also, it allows another way to access properties of req, res and inject without any decorators.

• #context tachijs will set req, res and inject method to this property. So, when unit testing, it is not defined.
  • #context.req Raw express request instance
  • #context.req Raw express response instance
  • #inject<S>(key: string): S A method to access a registered service by the given key. It is almost same to @inject decorator. (@inject<ServiceTypes.SomeService> someService: SomeService => const someService = this.inject<SomeService>(ServiceTypes.SomeService))
• #end(data: any, encoding?: string, status?: number): EndResult
• #json(data: any, status?: number): JSONResult
• #redirect(location: string, status?: number): RedirectResult
• #render(view: string, locals?: any, callback?: RenderResultCallback, status?: number): RenderResult
• #sendFile(filePath: string, options?: any, callback?: SendFileResultCallback, status?: number): SendFileResult
• #send(data: any, status?: number): SendResult
• #sendStatus(status: number): SendStatusResult

Results

BaseResult

All of result classes must be extended from BaseResult because tachijs can recognize results by instanceof BaseResult.

It has only one abstract method which must be defined by descendant classes.

• execute(req: express.Request, res: express.Response, next: express.NextFunction): Promise<any> tachijs will use this method to finalize response.

new EndResult(data: any, encoding?: string, status: number = 200)

tachijs will finalize response with res.status(status).end(data, encoding).

new JSONResult(data: any, status: number = 200)

tachijs will finalize response with res.status(status).json(data).

new NextResult(error?: any)

tachijs will finalize response with next(error).

new RedirectResult(location: string, status?: number)

tachijs will finalize response with res.redirect(location) (or res.redirect(status, location) if the status is given).

new RenderResult(view: string, locals?: any, callback?: RenderResultCallback, status: number = 200)

tachijs will finalize response with res.status(status).render(view, locals, (error, html) => callback(error, html, req, res, next))

type RenderResultCallback = (
  error: Error | null,
  html: string | null,
  req: express.Request,
  res: express.Response,
  next: express.NextFunction
) => void

new SendFileResult(filePath: string, options: any, callback?: SendFileResultCallback, status: number = 200)

tachijs will finalize response with res.status(status).sendFile(filePath, options, (error) => callback(error, req, res, next))

type SendFileResultCallback = (
  error: Error | null,
  req: express.Request,
  res: express.Response,
  next: express.NextFunction
) => void

new SendResult(data: any, status: number = 200)

tachijs will finalize response with res.status(status).send(data).

new SendStatusResult(status: number)

tachijs will finalize response with res.sendStatus(status).

@inject(key: string)

Inject a registered service in container by the given key.

class Injector

new Injector<C>(container: C)

Instantiate an injector with container

#instantiate(Constructor: any): any

Instantiate a service constructor. If the constructor has injected services, this method instantiate and inject them by #inject method.

#inject<S = any>(key: string): S

Instantiate a service by a key from Container. If there is no service for the given key, it will throws an error.

License

MIT © Junyoung Choi