Prisma Class Validator Generator

Common errors

• Error: Generator 'class_validator' could not be found.

  cause The `prisma-class-validator-generator` package is not installed or not accessible in the project's node_modules.
  fix Run `npm install prisma-class-validator-generator` or `yarn add prisma-class-validator-generator` in your project.

• Cannot find module './generated/models' or './generated/models/User'

  cause The generated files do not exist or the import path is incorrect. This usually happens if `npx prisma generate` hasn't been run, or if the `output` path in `schema.prisma` differs from the import statement.
  fix Ensure you've run `npx prisma generate` successfully. Verify the `output` path in your `schema.prisma` generator configuration matches your import path, and check if the files were indeed created at the specified location.

• Validation fails unexpectedly for incoming JSON objects, even with seemingly correct data.

  cause `class-validator` requires class instances to apply validation decorators. If you're passing plain JavaScript objects (e.g., from an API request body) directly to `validate()`, the decorators won't be applied.
  fix Use `class-transformer`'s `plainToClass` function to convert your plain object into an instance of the generated class before calling `validate()`. Example: `const instance = plainToClass(MyGeneratedClass, plainObject); await validate(instance);`

Warnings

• breaking Version 6.0.0 introduced a breaking change for `Bytes` fields, now supporting `Uint8Array` instead of `Buffer`. Projects using `Bytes` types in Prisma schemas will need to update their handling of these fields accordingly.
  Fix: Migrate any custom logic or validations related to Prisma `Bytes` fields to use `Uint8Array` instead of Node.js `Buffer` instances.
• breaking Version 5.0.0 primarily upgraded support to Prisma 5.x. Users on older Prisma versions (4.x or earlier) should expect breaking changes and are required to upgrade their Prisma client and schema to be compatible.
  Fix: Upgrade your `prisma` and `@prisma/client` packages to version 5.x or newer and run `npx prisma generate`. Review Prisma's official migration guides for specific changes.
• gotcha The generator requires a `prisma-client` or `prisma-client-js` generator to be present and configured in the same `schema.prisma` file for proper type inference and functionality. Without it, the generator may fail or produce incorrect output.
  Fix: Ensure your `schema.prisma` file includes a `generator client` block, e.g., `generator client { provider = "prisma-client" output = "../generated/prisma-client" }`.
• gotcha Version 6.x requires Node.js 18+ and TypeScript 5.8+. Using older versions may lead to build errors or runtime incompatibilities.
  Fix: Upgrade your Node.js environment to version 18.18+, 20.9+, or 22.11+ and your TypeScript dependency to 5.8+.

Install

• npm install prisma-class-validator-generator npm
• yarn add prisma-class-validator-generator yarn
• pnpm add prisma-class-validator-generator pnpm

Imports

• User
  wrong:

  const User = require('./generated/models');

  correct:

  import { User } from './generated/models';

  This imports a generated model class. The path 'generated/models' assumes the default output directory and single file generation. Adjust the path if 'output' is configured differently or `outputToMultipleFiles` is enabled.
• validate
  wrong:

  const validate = require('class-validator').validate;

  correct:

  import { validate } from 'class-validator';

  The core function from `class-validator` to perform validation on an instance of a generated class.
• plainToClass
  wrong:

  import { plainToClass } from 'class-validator';

  correct:

  import { plainToClass } from 'class-transformer';

  Crucial for validating plain JavaScript objects (e.g., from API requests) as `class-validator` requires class instances to apply decorators. `class-transformer` is a common companion library.

Quickstart

This quickstart demonstrates how to configure the `prisma-class-validator-generator` in your Prisma schema, generate the TypeScript models, and then use `class-validator` along with `class-transformer` to validate data against the generated `User` class.

/* schema.prisma */
generator client {
  provider = "prisma-client"
  output   = "../generated/prisma-client"
}

generator class_validator {
  provider = "prisma-class-validator-generator"
  output   = "./generated"
}

model User {
  id    Int     @id @default(autoincrement())
  email String  @unique
  name  String?
  posts Post[]
}

model Post {
  id        Int      @id @default(autoincrement())
  createdAt DateTime @default(now())
  updatedAt DateTime @updatedAt
  title     String
  content   String?
  published Boolean  @default(false)
  viewCount Int      @default(0)
  author    User?    @relation(fields: [authorId], references: [id])
  authorId  Int?
  rating    Float
}

/* Usage in TypeScript file */
import { User } from './generated/models';
import { validate } from 'class-validator';
import { plainToClass } from 'class-transformer';

async function validateUser(userData: any) {
  const userInstance = plainToClass(User, userData);
  const errors = await validate(userInstance);

  if (errors.length > 0) {
    console.error('Validation failed:', errors);
    return false;
  } else {
    console.log('Validation successful!');
    return true;
  }
}

// Example usage:
validateUser({ email: 'test@example.com', name: 'John Doe' });
validateUser({ email: 'invalid-email', name: 123 }); // This should fail

// To run this, first ensure `prisma generate` has been executed:
// npx prisma generate