Prisma Class Generator

Prisma

Prisma is Database ORM Library for Node.js, Typescript.

Prisma basically generate each models type definition defined in schema.prisma. Therefore, it does not require additional entry classes or repository layers.

This is Prisma's basic way of doing things, and I love this approach.

However, there are limitations because of these characteristics. A typical example is NestJS. In order to use @nestjs/swagger, the entity must be defined as class.

So I created a simple tool that generates a typescript file based on schema.prisma. The generated Classes are formatted with prettier, using the user's prettier config file if present. This will reduce the effort to define classes directly while using the same single source of truth (schema.prisma)

The Prisma JS Client returns objects that does not contain the model's relational fields. The Generator can create two separate files per model, one that matches the Prisma Js Client's interfaces, and one that contains only the relational fields. You can set the separateRelationFields option to true if you want to generate two separate classes for each model. The default value is false.

NestJS

NestJS is a framework for building efficient, scalable Node.js server-side applications.

and also, this is one of the frameworks with class and decorator as the basic structure.

Let's think about it like this: If the NestJS model is defined as class as below, it will be easier to apply swagger, TypeGraphQL, etc. through decorator.

And if the schema changes, redefine and create accordingly so that the schema and class syncs.

Using this library, it becomes possible.

export class Company {
	@ApiProperty({ type: Number }) // swagger
	@Field((type) => Int) // TypeGraphQL
	id: number

	@ApiProperty({ type: String }) // swagger
	name: string

	@ApiProperty({ type: Boolean }) // swagger
	isUse: boolean
}

If you set the separateRelationFields option to true and generate separate relational classes, you can compose a class from the two, only contanining the included relations. This example below is using methods from the @nestjs/swagger package. This example creates a class with all of the properties of the Product class and the category relational property from the generated relational class.

import { IntersectionType, PickType } from '@nestjs/swagger'
import { Product } from './product'
import { ProductRelations } from './product_relations'

export class ProductDto extends IntersectionType(
	Product,
	PickType(ProductRelations, ['category'] as const),
) {}

Usage

1. Install

   npm install prisma-class-generator
   yarn add prisma-class-generator

2. Define Generator in schema.prisma

   generator prismaClassGenerator {
       provider = "prisma-class-generator"
   }

3. 😎 done! Let's check out generated files.

   if this models were defined in your prisma.schema file,

   model Product {
     id            Int         @id
     title         String      @db.VarChar(255)
     desc          String      @db.VarChar(1024)
     images        Json        @db.Json
     isShown       Boolean?    @default(false)
     stock         Int?        @default(0)
     type          ProductType
     averageRating Float?
     categoryId    Int
     companyId     Int
     category      Category    @relation(fields: [categoryId], references: [id])
     company       Company     @relation(fields: [companyId], references: [id])
     createdAt     DateTime    @default(now()) @db.Timestamp(6)
     updatedAt     DateTime    @updatedAt @db.Timestamp(6)
   }
   
   model Category {
     id       Int       @id
     products Product[]
   }
   
   model Company {
     id          Int       @id
     name        String
     totalIncome BigInt
     lat         Decimal
     lng         Decimal
     by          Bytes
     products    Product[]
   }
   

   then this class is generated in <PROJECT_PATH>/src/_gen/prisma-class.

   ( The generating path can be customized through output option. )

   // category.ts
   import { Product } from './product'
   import { ApiProperty } from '@nestjs/swagger'
   
   export class Category {
   	@ApiProperty({ type: Number })
   	id: number
   
   	@ApiProperty({ isArray: true, type: () => Product })
   	products: Product
   }

   // product.ts
   import { Product } from './product'
   import { ApiProperty } from '@nestjs/swagger'
   
   export class Company {
   	@ApiProperty({ type: Number })
   	id: number
   
   	@ApiProperty({ type: String })
   	name: string
   
   	@ApiProperty({ type: Bigint })
   	totalIncome: bigint
   
   	@ApiProperty({ type: Number })
   	lat: number
   
   	@ApiProperty({ type: Number })
   	lng: number
   
   	@ApiProperty({ type: Buffer })
   	by: Buffer
   
   	@ApiProperty({ isArray: true, type: () => Product })
   	products: Product
   }

   // category.ts
   import { Category } from './category'
   import { Company } from './company'
   import { ProductType } from '@prisma/client'
   import { ApiProperty } from '@nestjs/swagger'
   
   export class Product {
   	@ApiProperty({ type: Number })
   	id: number
   
   	@ApiProperty({ type: String })
   	title: string
   
   	@ApiProperty({ type: String })
   	desc: string
   
   	@ApiProperty()
   	images: any
   
   	@ApiProperty({ type: Boolean })
   	isShown: boolean
   
   	@ApiProperty({ type: Number })
   	stock: number
   
   	@ApiProperty({ enum: ProductType, enumName: 'ProductType' })
   	type: ProductType
   
   	@ApiProperty({ type: Number })
   	averageRating: number
   
   	@ApiProperty({ type: Number })
   	categoryId: number
   
   	@ApiProperty({ type: Number })
   	companyId: number
   
   	@ApiProperty({ type: () => Category })
   	category: Category
   
   	@ApiProperty({ type: () => Company })
   	company: Company
   
   	@ApiProperty({ type: Date })
   	createdAt: Date
   
   	@ApiProperty({ type: Date })
   	updatedAt: Date
   }

   // index.ts
   import { Product as _Product } from './product'
   import { Category as _Category } from './category'
   import { Company as _Company } from './company'
   
   export namespace PrismaModel {
   	export class Product extends _Product {}
   	export class Category extends _Category {}
   	export class Company extends _Company {}
   
   	export const extraModels = [Product, Category, Company]
   }

   The reason why classes were grouped into the 'PrismaModel' namespace and distributed in the index.ts file.

   1. First, generated classes can overlap with the model types generated by Prisma, causing confusion.
   2. when using Swagger in Nest.JS, you can use this array data in Bootstrap code to scan classes into @nestjs/swagger without having to list them.

   There is a reference code for this below.

   // main.ts in Nest.JS application
   import { PrismaModel } from './_gen/prisma-class'
   
   const document = SwaggerModule.createDocument(app, options, {
   	extraModels: [...PrismaModel.extraModels],
   })

   You can also disable it through the makeIndexFile option.

Supported options

• dryRun
  • Decide whether to write file or just print result. default value is true
    • if you finished check result via terminal, then you should this options to false
• output
  • sets output path. default is '../src/_gen/prisma-class'
• useSwagger
  • generates swggger decorator. default value is true
• makeIndexFile
  • makes index file, default value is true
• separateRelationFields
  • puts relational fields into different file for each model. This way the class will match the object returned by a Prisma query, default value is false
• clientImportPath
  • set prisma client import path manually, default value is @prisma/client
• useNonNullableAssertions
  • Apply a ! after non-optional class fields to avoid strict mode warnings (Property has no initializer and is not definitely assigned in the constructor.)
• preserveDefaultNullable
  • Determines how null fields are handled. When set to false (default), it turns all null fields to undefined. Otherwise, it follows Prisma generation and adds null to the type.

How it works?

Prima internally defines metadata as a dmmf object.

prisma-class-generator can automate class definition using this dmmf.

It is defined as an additional generator in the schema.prisma file and will operate in the prisma generate process.

Feature

• generate Classes from prisma model definition
• Support Basic Type and Relation
• Support option to generate Swagger Decorator
• Format generated Classes with prettier, using the user's prettier config file if present

Future Plan

• Considers all class-based things that are not limited to Nest.JS
• Support all types in prisma.schema
• Support TypeGraphQL
• Support DTO
• Support custom path, case or name per each model

FAQ

1. Is it CRUD Generator?

No. It will not provide functions such as "nestjs CRUD generate". I think it is outside the scope of this library. Instead, it will only serve as a bridge connecting the Prisma model and (entity)class.

It will focus on defining classes and then give the developer responsibility on how to use them.

This is because if too much is provided, the library becomes less adaptable accordingly.

2. Is only works with NestJS?

No, but of course, it goes well with NestJS. I'm also planning to support the library related to NestJS.

But even if you don't use NestJS, this library will be useful for you if you use class decorator based on reflect-metadata to develop web services.