After upgrading to 3.0.2, can't create or update records when json field is null

I’m having a similar error to https://github.com/prisma/prisma/issues/9199 after upgrading to Prisma 3.0.2 (from 2.x)

I have also ran prisma migrate with no changes in order to cohere with Upgrade Path for referential actions and named constraints

datamodel in particualar:

model Room {
  id        String    @id @default(cuid()) @db.VarChar(30)
  name      String
  updatedAt DateTime  @updatedAt
  createdAt DateTime  @default(now())
  accountId String    @map("account") @db.VarChar(30)
  bgColor   Json?
  account   Account   @relation(fields: [accountId], references: [id])
  bookings  Booking[]

  @@index([accountId])
}

Mutation from Nexus:

    t.field('createRoom', {
      type: 'Room',
      args: {
        name: nonNull(stringArg()),
        accountId: nonNull(idArg()),
        bgColor: arg({type: "Json"}),
      },
      resolve: (_parent, args, ctx) => ctx.prisma.room.create({
        data: {
          ...args
        }
      })
    });

Error when bgColor is null (the same thing when creating or updating):

Invalid `prisma.room.create()` invocation: { data: { name: 'Test Room', accountId: 'ckm7v6zpi00130huil8hbwvlk', bgColor: null ~~~~ } } Argument bgColor for data.bgColor must not be null. Please use undefined instead.```

_Originally posted by @chemicalkosek in https://github.com/prisma/prisma/issues/9199#issuecomment-919430264_

[chemicalkosek]

That would mean rewriting even the simplest resolvers such as

 resolve: (_parent, args, ctx) => ctx.prisma.room.create({
        data: {
          ...args
        }
      })

to check for json null values. Can we make a default that will transform the null value to the previous behaviour? Or such thing will not be possible?

[matthewmueller]

Hey everyone, sorry for the confusion here. This is expected, but we missed this in our documentation. We stopped allowing nulls for JSON field inputs because:

prisma.foo.update({ where: { ... }, data: { someJsonColumn: null }});

The above code is ambiguous:

• Did you mean setting someJsonField to the value null?
• Or did you mean setting someJsonField to the database NULL?

The solution is to use DbNull and JsonNull. To insert a null value into a Json field, you would write:

import { Prisma } from '@prisma/client'

prisma.log.create({
  data: {
    meta: Prisma.JsonNull,
  },
})

And to insert a database NULL into a Json field, you would write:

import { Prisma } from '@prisma/client'

prisma.log.create({
  data: {
    meta: Prisma.DbNull,
  },
})

We’re going to improve this error message and also fix up our documentation.