Table of Contents

• Motivation
• Installation
• Usage

Motivation

Motivation of this generator - fix typescript and prisma mismatch in case of "exact" types. In typescript, if value has all required fields and some extra fields - typescript will be satisfied:

type Person = {
  first: string, last: string
}

declare function savePerson(person: Person);

const tooFew = { first: 'Stefan' };
const exact = { first: 'Stefan', last: 'Baumgartner' }
const tooMany = { first: 'Stefan', last: 'Baumgartner', age: 37 }

savePerson(tooFew); // 💥 doesn't work
savePerson(exact); // ✅ satisfies the contract
savePerson(tooMany); // ✅ satisfies the contract

// example from "https://fettblog.eu/"

But despite typescript satisfaction, prisma will throw error in case of having extra fields being passed. As a solution - this generator creates utility functions to omit extra fields.

• github issue
• stackoverflow question

Installation

Using npm:

 npm i --save-dev prisma-generator-omit-extra-fields

Using yarn:

 yarn add -D prisma-generator-omit-extra-fields

Usage

1 - Add the generator to your Prisma schema

generator omitExtraFields {
  provider = "prisma-generator-omit-extra-fields"
  
  // optional parameter to change directory or name of generated file
  // if output is specified, it should contain filename of generated file
  // (output like "../generated" is invalid)
  output = "../generated/extra-fields.ts"
}

2- Run npx prisma generate for the following schema.prisma, or your schema

enum Role {
  Admin
  Default
}

model User {
  id        Int      @id @default(autoincrement())
  createdAt DateTime @default(now())
  updatedAt DateTime @updatedAt
  name      String
  email     String
  role      Role
}

3 - Now you're able to use generated functions. For above schema you'll get next functions:

  polishUser(user); // remove extra fields but has no explicit types
  polishDefaultUser(user); // remove extra fields and is suitable for "data" field in queries
  polistPartialUser(user); // remove extra fields and is suitalble for "where" field in queries 

Example of their usage:

const userWithExtraFields = {
  email: '[email protected]',
  name: 'test',
  role: 'Default',
  a: 1, // extra field
} as const;

// typescript is satisfied, but prisma will throw error
// because of extra field 'a: 1'
prisma.user.create({ data: userWithExtraFields });

// this one will be fine for prisma
prisma.user.create({ data: polishUser(userWithExtraFields) })

// or this one, if you want more excplicit types
prisma.user.create({ data: polishDefaultUser(userWithExtraFields) });
prisma.user.findFirst({ where: polishPartialUser(userWithExtraFields) });