Extending Types for Prisma Extensions in NextJS

If you read my previous post, you’ll note that I was very excited to try out Prisma’s new Extensions alongside their Middleware and try out various use cases. When test driving I did hit a snag rebuilding the Types for our new extension to pull through.

If you are running Prisma with NextJS you’ve probably followed this initial best practice doc: https://www.prisma.io/docs/guides/database/troubleshooting-orm/help-articles/nextjs-prisma-client-dev-practices

Here we define prisma in the global object so that we don’t create a bazillion instances of Prisma and have the world crashing down on us. If you are using Typescript, this global instance was probably Typed. in our case we had:

declare global {
  // eslint-disable-next-line no-var
  var prisma: PrismaClient | undefined;
}

The Issue

The issue is that the type PrismaClient has no clue about our new Extensions or the types within. In this use case, we are attempting to create a new signUp method on the User model.

const extendedPrisma = prisma.$extends({
    model: {
      user: {
        async signUp(args: SignUpArgs): Promise<UserWithRelations> {
          return await prisma.user.create({
            ...args,
          });
        },
      },
    },
  });

So how do we fix this?…

The Solution

Turn const prisma from the previous example into a function that returns the newly created extendedPrisma context. When setting the global prisma value we use this value and Type instead. Now when we import prisma it should include our new model action signUp and type validations as seen below.

The Code

import {
  Prisma,
  PrismaClient,
  Profile,
  User,
} from '@prisma/client';

export const defaultUserSessionIncludes = {
  profile: true,
} as Prisma.UserCreateArgs['include'];

export type UserWithRelations = User & {
  profile: Profile;
};

// Set default prisma logs. More logs in debug mode.
const logOptions: Prisma.LogLevel[] = process.env.DEBUG ? ['query', 'error'] : ['error'];

type UserCreateArgsWithProfile = Omit<Prisma.UserCreateArgs['data'], 'profile'> & {
	// Require Profile for signup  
	profile: Prisma.UserCreateArgs['data']['profile']; 
};

// mimics Prisma.UserCreateArgs
type SignUpArgs = {
  data: UserCreateArgsWithProfile;
  include?: Prisma.UserCreateArgs['include'];
};

const extendedPrismaClient = () => {
  const prisma = new PrismaClient({
    log: logOptions,
  });

  const extendedPrisma = prisma.$extends({
    model: {
      user: {
        async signUp(args: SignUpArgs): Promise<UserWithRelations> {
          return await prisma.user.create({
            ...args,
          });
        },
      },
    },
  });

  return extendedPrisma;
};

export type ExtendedPrismaClient = ReturnType<typeof extendedPrismaClient>;

/**
 * Instantiate prisma client for Next.js:
 * https://www.prisma.io/docs/support/help-articles/nextjs-prisma-client-dev-practices#solution
 */

declare global {
  // eslint-disable-next-line no-var
  var prisma: ExtendedPrismaClient | undefined;
}

export const prisma = global.prisma || extendedPrismaClient();

if (process.env.NODE_ENV !== 'production') {
  global.prisma = prisma;
}

export async function disconnect() {
  await prisma.$disconnect();

  return true;
}

export async function connect() {
  await prisma.$connect();

  return true;
}

If you are using Next-Auth

One other note if you are using Next-Auth. We kept hitting a snag with the types for Next-Auth’s PrismaAdapter

Again, it expects a type of PrismaClient but we want to pass our new ExtendedPrismaClient type instead.

There was a weird type of error trying to recast this for some reason complaining about Prisma’s $use missing on our type. Remembering this is still in the Experimental Phase. We didn’t try to dive in too hard here, rather we cast as unknown first before passing along the types expected for the adapter. While not ideal, it does work and is something we’ll monitor as Prisma continues to wrap this feature up.

export const authOptions: NextAuthOptions = {
  adapter: CustomPrismaAdapter(prisma as unknown as ExtendedPrismaClient),
  ... 
}

function CustomPrismaAdapter(p: ExtendedPrismaClient) {
  const prismaAdapter = PrismaAdapter(p as unknown as PrismaClient);
...
}

That’s all folks!

Remember to restart that Typescript Server folks. 🙂 I kept battling this a few times only to realize I needed to “turn it off and on again”. Once set, you’ll be ready to keep tacking on new extensions and middleware!