prisma: When using a `connect` or `create` block in a `create()` or `update()`, other scalar relation fields cannot be used directly

Bug description

I have a model with multiple relations to single entities. When I try to .create with this model, I have the option of providing those relations via passing the IDs of the foreign entities to the _id columns, or I can use Prisma’s relations to perform a connect: {}.

However, when I want to perform a nested write, creating one of the related entities when I create the main entity, I am not able to pass the ID to create the other relation - prisma requires me to use the connect: {} method instead.

This feels like a bug.

Apologies if this is already an Issue, I’m not really sure how to articulate a search for this.

How to reproduce

Given this schema:

model MainItem {
  id                  Int            @id @default(autoincrement())
  related_item_one_id Int
  related_item_one    RelatedItemOne @relation("main_item__to__related_item_one", fields: [related_item_one_id], references: [id])
  related_item_two_id Int
  related_item_two    RelatedItemTwo @relation("main_item__to__related_item_two", fields: [related_item_two_id], references: [id])
}

model RelatedItemOne {
  id       Int        @id @default(autoincrement())
  api_keys MainItem[] @relation("main_item__to__related_item_one")
}

model RelatedItemTwo {
  id       Int        @id @default(autoincrement())
  api_keys MainItem[] @relation("main_item__to__related_item_two")
}

This works fine:

prisma.mainItem.create({
  data: {
    related_item_one_id: 123,
    related_item_two_id: 456,
  }
})

However, this throws a TypeError:

prisma.mainItem.create({
  data: {
    related_item_one_id: 123, 
    related_item_two: {
      connect: {
        id: 456
      }
    },
  }
})

// Types of property 'related_item_one_id' are incompatible.
//   Type 'number' is not assignable to type 'undefined'. ts(2322)

That example is somewhat less useful though than my current use case: performing a nested write to create the related entity. This works fine:

prisma.mainItem.create({
  data: {
    related_item_one: {
      connect: {
        id: 123
      }
    },
    related_item_two: {
      create: {}
    },
  }
})

However, this throws the TypeError:

prisma.mainItem.create({
  data: {
    related_item_one_id: 123,
    related_item_two: {
      create: {}
    },
  }
})

// Types of property 'related_item_one_id' are incompatible.
//   Type 'number' is not assignable to type 'undefined'. ts(2322)

Expected behavior

I would expect these more terse versions to be valid.

Prisma information

(see above)

Environment & setup

• OS: Mac OS
• Database: PostgreSQL
• Node.js version: “12.20.1”
• Prisma version: “2.21.2”