prisma-generator-omit-extra-fields

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:

1type Person = {
2  first: string, last: string
3}
4
5declare function savePerson(person: Person);
6
7const tooFew = { first: 'Stefan' };
8const exact = { first: 'Stefan', last: 'Baumgartner' }
9const tooMany = { first: 'Stefan', last: 'Baumgartner', age: 37 }
10
11savePerson(tooFew); // 💥 doesn't work
12savePerson(exact); // ✅ satisfies the contract
13savePerson(tooMany); // ✅ satisfies the contract
14
15// 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.

Links related to this problem:

• github issue
• stackoverflow question

Installation

Using npm:

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

Using yarn:

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

Usage

1 - Add the generator to your Prisma schema

1generator omitExtraFields {
2  provider = "prisma-generator-omit-extra-fields"
3  
4  // optional parameter to change directory or name of generated file
5  // if output is specified, it should contain filename of generated file
6  // (output like "../generated" is invalid)
7  output = "../generated/extra-fields.ts"
8}

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

1enum Role {
2  Admin
3  Default
4}
5
6model User {
7  id        Int      @id @default(autoincrement())
8  createdAt DateTime @default(now())
9  updatedAt DateTime @updatedAt
10  name      String
11  email     String
12  role      Role
13}

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

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

Example of their usage:

1const userWithExtraFields = {
2  email: 'test@gmail.com',
3  name: 'test',
4  role: 'Default',
5  a: 1, // extra field
6} as const;
7
8// typescript is satisfied, but prisma will throw error
9// because of extra field 'a: 1'
10prisma.user.create({ data: userWithExtraFields });
11
12// this one will be fine for prisma
13prisma.user.create({ data: polishUser(userWithExtraFields) })
14
15// or this one, if you want more excplicit types
16prisma.user.create({ data: polishDefaultUser(userWithExtraFields) });
17prisma.user.findFirst({ where: polishPartialUser(userWithExtraFields) });