validated-service

Easily build reliable service with Typescript.

Motivation

I love working on software architecture, quality and scaling.

Note : In my softwares architecture, I gather requests / API calls under what I call a service.

I've recently been working on a web and mobile project where I made tons of API call, and I came to some conclusions :

• My way of handling API calls was terrible.
• Not only was it terrible, it's way too common.

What am I talking about ? What do you think of :

api.ts

import axios from 'axios';
 
export const api = axios.create({
  baseURL: 'http://localhost:80',
});

login.service.ts

import { api } from './api.ts';
 
type UserToLoginDto = {
  email: string;
  password: string;
};
 
export async function loginService({ email, password }: UserToLoginDto) {
  return api
    .post('/auth/login', { email, password })
    .then((response) => ({ user: response.data.user, token: response.data.token.accessToken }))
    .catch((e) => {
      if (e.response.status === 401) throw new Error('bad-password');
      else throw new Error('unknown');
    });
}

This is what I've been taught, what I've doing and what I see most people do around me.

This is fundamentally terrible for the following reasons :

• If the data sent by the server doesn't have the format I expect, my whole application might crash or display bad informations.
• These problems come with a very low level of monitoring possible as to : why is this happening ?
• If my strategy is to throw an error "unknown" when I don't understand what's happening, i'll need to duplicate this everywhere
• This example lack strict typing

From this point, my questions were :

• How do I validate data sent by an endpoint ?
• What do I do if it's not valid ?
• How to make this process easy and straightforward
• How to make this process modulable if :
  • I want to monitor invalid responses
  • On some occasions, I'm able and wish to make an invalid response work.
  • Monitor it differently if I make and invalid response work.

Features

• Made with TypeScript
• @mrtd/services allow you to generate services :
  • Where you can validate responses with your own strategies.
  • Using your own error handling.
  • With a straightforward builder class.
  • Is shipped with default strategies I would recommend.
• Comes bundled with a CLI : service-build-dto.
  • Allow you to generate json-schemas from the *response.dto.ts definitions you have to validate.

Code Example

Installation

npm install --save validated-service

Or

yarn add validated-service

Add the following scripts in your package.json and run it when you need to compile *response.do.ts to files to json-schemas :

"schema": "service-build-dto"

License

MIT