Define type of content of Json field

Problem

Right now if you have the following schema with Json field:

model User {
  id               Int  @default(autoincrement()) @id
  name             String?
  extendedProfile  Json
}

You’ll end up with a problem that you don’t have strict type for extendedProfile field in .ts.

const user = prismaService.user.findOne(...);
user.extendedProfile // we don't know the type of extendedProfile

The one way to fix it, is specify some interface in your code and use it like this:

interface UserProfile {
    field1: string;
    field2: number;
}

const user = prismaService.user.findOne(...);
(user.extendedProfile as UserProfile).field1; // now we have autocompletion

But it’s not really comfortable to use it like that each time.

Also we can create some class and create instance of it like that:

interface UserProfile {
    field1: string;
    field2: number;
}

class User {
    id: string;
    name?: string;
    extendedProfile: UserProfile;

    constructor(user: PrismaUser /* user object returned by prisma */) {
        // ... initialize
    }
}

const user = new User(prismaService.user.findOne(...));

But this solution creates some overhead due to the creation of an additional object.

Suggested solution

Maybe we can specify type in schema.prisma file like that?

json ExtendedUserProfileJson {
    field1  String
    field2  Int
}

model User {
  id               Int  @default(autoincrement()) @id
  name             String?
  extendedProfile  ExtendedUserProfileJson
}

Alternatives

Alternatively, we can somehow manage this in the typescript.

[janpio]

Being able to type your Json fields is a simple and understandable feature requests. Although there might be workarounds, this might very well be something that Prisma could offer in the future on its own - so having this feature request is valid.

[eakriulin]

Up — we really need this feature 🚀