Add type to a Prisma JSON fields

Using the external package prisma-json-types-generator you can type JSON fields in Prisma.

1. Install and configure the package adding the json provider.

   generator client {
     provider = "prisma-client-js"
   }
   
   /// Always after the prisma-client-js generator
   generator json {
     provider = "prisma-json-types-generator"
   }
   

2. Then update your model adding the type by using abstract syntax tree comments.

   model User {
      id Int @id
      /// [UserAddress] <- Your type here
      address Json
   }
   

3. Finally declare the PrismaJson namespace adding your type.

   declare global {
     namespace PrismaJson {
       interface UserAddress {
         city: string
         street: string
         postalCode: number
       }
     }
   }
   

   Important: Make sure the file has the extension .d.ts. Otherwise your types may not work.

Every time that you changed your declarations types, you need to migrate the scheme to implement it.

For more information visit Prisma documentation and the prisma-json-types-generator package.