Improve error messages for missing back-relation field

With this Prisma schema:

model Event {
  id        Int      @id @default(autoincrement())
  owner     Person   @relation(name: "EventOwners")
  recipient Person?  @relation(name: "EventRecipients")
}

model Person {
  id        Int      @id @default(autoincrement())

}

I get this error VS Code:

Error validating model "Event": Automatic related field generation would cause a naming conflict. Please add an explicit opposite relation field.

The solution here is fairly straightforward (i.e. adding back-relation fields) but it’s not clear from the error message itself.

An improved error would be a bit more actionable, e.g.:

Please add the opposing relation field on the other model. 

Or even (if possibl):

Please add the opposing relation field on the `Person` model. 

[nikolasburk]

Hey @keepforever, Prisma always requires both relation fields to be present per relation. Since you want to create two relations, you need to have two relation fields on each side:

model User {
  id    Int     @default(autoincrement()) @id
  email String  @unique
  name  String?
  head  Note[]  @relation("head")
  torso Note[]  @relation("torso")
}

model Note {
  id        Int    @default(autoincrement()) @id
  title     String
  content   String
  userTorso User   @relation("head", fields: [userId], references: [id])
  userHead  User   @relation("torso", fields: [userId], references: [id])
  userId    Int
}

You can find more info in the docs.

[richardwardza]

To finish this off, my final solution is to reverse the references and store the id on the User tables and not the Image table:

model User {
  id         Int    @default(autoincrement()) @id
  name       String
  profilePic Image?  @relation("ProfilePicture", fields: [profileImageId], references: [id])
  avatar     Image?  @relation("AvatarImage", fields: [avatarImageId], references: [id])
  profileImageId  Int? @map("userProfilePic")
  avatarImageId   Int? @map("userAvatar")
}

model Image {
  id             Int    @default(autoincrement()) @id
  name           String
  userProfilePic User? @relation("ProfilePicture")
  userAvatar     User? @relation("AvatarImage")
 }

My database looks a lot saner:

CREATE TABLE "play"."User" (
  "id" int4 NOT NULL DEFAULT nextval('"play"."User_id_seq"'::regclass),
  "name" text COLLATE "pg_catalog"."default" NOT NULL,
  "userAvatar" int4,
  "userProfilePic" int4,
  CONSTRAINT "User_pkey" PRIMARY KEY ("id"),
  CONSTRAINT "User_userAvatar_fkey" FOREIGN KEY ("userAvatar") REFERENCES "play"."Image" ("id") ON DELETE SET NULL ON UPDATE CASCADE,
  CONSTRAINT "User_userProfilePic_fkey" FOREIGN KEY ("userProfilePic") REFERENCES "play"."Image" ("id") ON DELETE SET NULL ON UPDATE CASCADE
);

CREATE UNIQUE INDEX "User_userAvatar" ON "play"."User" USING btree (
  "userAvatar" "pg_catalog"."int4_ops" ASC NULLS LAST
);

CREATE UNIQUE INDEX "User_userProfilePic" ON "play"."User" USING btree (
  "userProfilePic" "pg_catalog"."int4_ops" ASC NULLS LAST
);

CREATE TABLE "play"."Image" (
  "id" int4 NOT NULL DEFAULT nextval('"play"."Image_id_seq"'::regclass),
  "name" text COLLATE "pg_catalog"."default" NOT NULL,
  CONSTRAINT "Image_pkey" PRIMARY KEY ("id")
);

My query:

const user = await prisma.user.create({
    data: {
        name: "user 1",
        profilePic: { create: { name: "profile pic 1" } },
        avatar: { create: { name: "avatar pic" } }
    },
    include: {
        profilePic: true,
        avatar: true
    }
})

returns:

user:  {
  id: 1,
  name: 'user 1',
  profileImageId: 1,
  avatarImageId: 2,
  profilePic: { id: 1, name: 'profile pic 1' },
  avatar: { id: 2, name: 'avatar pic' }
}

This now looks like the ramblings of a madman but leaving them here to hopefully help anyone coming after.