@hatkom/prisma-generator-default-values

A Prisma generator that exposes the @default(...) values from your schema as typed, importable constants.

Why?

Prisma schemas define default values, but there's no way to access them at runtime. If you want to apply defaults in your application layer (e.g. for optimistic UI, form pre-filling, or validation), you end up duplicating them manually.

This generator reads your schema and produces a TypeScript file with all default values exported as as const objects.

Installation

npm i @hatkom/prisma-generator-default-values

Setup

Add the generator to your schema.prisma:

generator default_values {
  provider = "prisma-generator-default-values"
  output   = "./generated/defaults.ts"
}

Then run:

npx prisma generate

Example

Given this schema:

enum Role {
  USER
  ADMIN
}

model User {
  id        String   @id @default(cuid())
  email     String   @unique
  name      String?
  role      Role     @default(USER)
  active    Boolean  @default(true)
  createdAt DateTime @default(now())
}

model Post {
  id        String   @id @default(uuid())
  title     String
  published Boolean  @default(false)
  views     Int      @default(0)
  authorId  String
  author    User     @relation(fields: [authorId], references: [id])
}

The generator produces:

// Generated by prisma-generator-default-values — do not edit manually

export const UserDefaults = {
  id: { _fn: 'cuid' },
  role: "USER",
  active: true,
  createdAt: { _fn: 'now' },
} as const

export const PostDefaults = {
  id: { _fn: 'uuid' },
  published: false,
  views: 0,
} as const

What gets generated

For each model that has fields with @default(...), a {Model}Defaults const object is exported. The as const assertion gives you full literal types out of the box.

Default value representation

| Schema default | Generated value | |---|---| | @default("VALUE") | "VALUE" | | @default(true) | true | | @default(0) | 0 | | @default(ENUM_VALUE) | "ENUM_VALUE" | | @default(now()) | { _fn: 'now' } | | @default(uuid()) | { _fn: 'uuid' } | | @default(cuid()) | { _fn: 'cuid' } | | @default(autoincrement()) | { _fn: 'autoincrement' } | | @default(dbgenerated("...")) | { _fn: 'dbgenerated', _args: [...] } |

Scalar and enum defaults become their literal value. Function-based defaults (like now(), uuid()) become { _fn: 'name' } objects, with an _args array when the function has arguments.

Usage examples

import { UserDefaults, PostDefaults } from './generated/defaults'

// Pre-fill a form
const newUser = {
  role: UserDefaults.role,       // "USER"
  active: UserDefaults.active,   // true
}

// Check if a field has a server-generated default
if (typeof UserDefaults.id === 'object' && '_fn' in UserDefaults.id) {
  // id is generated server-side (cuid), don't include in form
}

License

MIT