[TypeStack] Make FoalTS more "DRY": serialization, validation & OpenAPI generation

[LoicPoullain]

Issue

Writing a simple REST API can be quite repetitive in Foal because we may have to write the same thing three times: the entity, the validation schema (AJV) and the OpenAPI request body.

The version 1 of Foal (June Release) will include a new feature to directly generate the OpenAPI request body from the validation schema thus reducing the code redundancy. #454

But this requires the developer to still define both the entity and validation schema.

Some libraries already exist to take care of this (including the serialization) and we could have an easy way to integrate them with Foal: class-validator, class-transformer, class-validator-jsonschema.

Related issue: #276

Constraints

• FoalTS should still support the current way of building an API (with @ValidateBody, etc).
• At any time, developers should be able to regain control on these hooks if necessary (especially when the API becomes more complex).

Possible solution

Add these hooks:

@ValidateBodyFromClass(c: Class)

@ApiRequestBodyFromClass(c: Class)

@SerializeBodyFromClass(c: Class)

@SerializeAndValidateBodyFromClass(c: Class)

Usage

// social-post.entity.ts
import { Contains, IsEmail, IsFQDN, IsInt, Length, Max, Min } from 'class-validator';
import { Column, Entity, PrimaryGeneratedColumn } from 'typeorm';

@Entity()
export class SocialPost {

    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    @Length(10, 20)
    title: string;

    @Column()
    @Contains('hello')
    text: string;

    @Column()
    @IsInt()
    @Min(0)
    @Max(10)
    rating: number;

    @Column()
    @IsEmail()
    email: string;

    @Column()
    @IsFQDN()
    site: string;

}

// social-post.controller.ts
import { Context, Post, HttpResponseCreated } from '@foal/core';
import { SocialPost } from '../entities';
import { ApiRequestBodyFromClass, ValidateBodyFromEntity } from 'somewhre';

export class SocialPostController {

  @Post('/')
  @ValidateBodyFromEntity(SocialPost)
  @ApiRequestBodyFromClass(SocialPost)
  createSocialPost(ctx: Context) {
    return new HttpResponseCreated();
  }

  // OR

  @Post('/')
  @ValidateBodyFromEntity(SocialPost, { /* options */ })
  @ApiRequestBodyFromClass(SocialPost, { /* options */ })
  createSocialPost(ctx: Context) {
    return new HttpResponseCreated();
  }
}

[LoicPoullain]

Package added in v1.2.0