prisma-typed-json-generator

A Prisma generator that automatically creates TypeScript types for your Json fields with @type() annotations, and patches the generated Prisma Client types to use your custom types.

Features

• Extracts custom types from commented blocks in your Prisma schema.
• Generates a prisma-json.types.ts file in your Prisma Client output directory.
• Patches the generated index.d.ts to use your custom types for annotated Json fields, using a namespace import to avoid type name clashes.
• Context-aware: only patches the correct field in the correct model, even if multiple models use the same field name.

Usage

1. Add the generator to your schema.prisma:

generator client {
  provider = "prisma-client-js"
  output   = "./client"
}

generator prisma_types_json_generator {
  provider = "prisma-typed-json-generator"
  output   = "../types"
}

2. Annotate your Json fields with @type() and define your types in comments:

// type Address {
//   street string
//   city string
//   country string
// }

model User {
  id      Int     @id @default(autoincrement())
  email   String  @unique
  name    String?
  address Json // @type(Address)
}

3. Run prisma generate:

npx prisma generate

4. The generator will:
   • Create prisma-json.types.ts in your client output directory.
   • Patch index.d.ts to use PrismaJsonTypes.Address for the address field in the User model.

Why?

Prisma's Json fields are typed as Prisma.JsonValue by default, which is not type-safe. This generator lets you use your own types for better safety and DX.

License

MIT