Typescript throw error when abstracting nested select

[ashlite]

Bug description

It is very easy to reproduce this, I don't know if it work as intended or not.

So I have this simple prisma schema, basically just a 3 relation table, A have B children, B have C children. All have 1 to many relationship.

model A {
  id   Int    @id @default(autoincrement())
  col1 String @db.VarChar
  col2 String @db.VarChar

  listB B[]
}

model B {
  id   Int    @id @default(autoincrement())
  col1 String @db.VarChar
  col2 String @db.VarChar
  baId Int?

  aData A?  @relation(fields: [baId], references: [id], onDelete: Cascade, onUpdate: Cascade)
  listC C[]
}

model C {
  id   Int    @id @default(autoincrement())
  col1 String @db.VarChar
  col2 String @db.VarChar
  cbId Int?

  bData B? @relation(fields: [cbId], references: [id], onDelete: Cascade, onUpdate: Cascade)
}

then in my typescript, I keep it simple:

import { Prisma, PrismaClient } from '@prisma/client'

export const db = new PrismaClient()

const selectA: Prisma.ASelect = {
  id: true,
  col1: true,
  col2: true
}

const selectB: Prisma.BSelect = {
  id: true,
  col1: true,
  col2: true,
  aData: {
    select: selectA
  }
}

const selectC: Prisma.CSelect = {
  id: true,
  col1: true,
  col2: true,
  bData: {
    select: selectB
  }
}

const query1 = await db.c.findMany({
  select: selectC
})

const result1 = query1[0].bData.aData //error
const result2 = query1[0].bData?.baId

const query2 = await db.c.findMany({
  select: {
    id: true,
    col1: true,
    col2: true,
    bData: {
      select: {
        id: true,
        col1: true,
        col2: true,
        aData: {
          select: {
            id: true,
            col1: true,
            col2: true
          }
        }
      }
    }
  }
})

const result3 = query2[0].bData?.aData
const result4 = query2[0].bData?.baId //error

Result 1 throwing typescript error because aData is not exist in that type, while result2 works even though I'm not specifying it in the selectB. While the result 3 and 4 is working normally.
I'm scratching my head because it seems both query have same select but it throw different error in typescript. I tried to separate abstract selection and place it in the same files as my typeBox declaration so I can quickly check that my query will have same output as my type and can reuse select multiple times in multiple query.

How to reproduce

Expected behavior

Select working normally, typescript not throwing any error like in the query2

Prisma information

generator client {
  provider = "prisma-client-js"
}

datasource db {
  provider = "postgresql"
  url      = env("DATABASE_URL")
}

model A {
  id   Int    @id @default(autoincrement())
  col1 String @db.VarChar
  col2 String @db.VarChar

  listB B[]
}

model B {
  id   Int    @id @default(autoincrement())
  col1 String @db.VarChar
  col2 String @db.VarChar
  baId Int?

  aData A?  @relation(fields: [baId], references: [id], onDelete: Cascade, onUpdate: Cascade)
  listC C[]
}

model C {
  id   Int    @id @default(autoincrement())
  col1 String @db.VarChar
  col2 String @db.VarChar
  cbId Int?

  bData B? @relation(fields: [cbId], references: [id], onDelete: Cascade, onUpdate: Cascade)
  listD D[]
}

model D {
  id   Int    @id @default(autoincrement())
  col1 String @db.VarChar
  col2 String @db.VarChar
  dcId Int?

  cData C? @relation(fields: [dcId], references: [id], onDelete: Cascade, onUpdate: Cascade)
}

import { Prisma, PrismaClient } from '@prisma/client'

export const db = new PrismaClient()

const selectA: Prisma.ASelect = {
  id: true,
  col1: true,
  col2: true
}

const selectB: Prisma.BSelect = {
  id: true,
  col1: true,
  col2: true,
  aData: {
    select: selectA
  }
}

const selectC: Prisma.CSelect = {
  id: true,
  col1: true,
  col2: true,
  bData: {
    select: selectB
  }
}

const query1 = await db.c.findMany({
  select: selectC
})

const result1 = query1[0].bData.aData
const result2 = query1[0].bData?.baId

const query2 = await db.c.findMany({
  select: {
    id: true,
    col1: true,
    col2: true,
    bData: {
      select: {
        id: true,
        col1: true,
        col2: true,
        aData: {
          select: {
            id: true,
            col1: true,
            col2: true
          }
        }
      }
    }
  }
})

const result3 = query2[0].bData?.aData
const result4 = query2[0].bData?.baId

Environment & setup

• OS: Windows
• Database: Postgresql
• Node.js version: 20.10.0

Prisma Version

prisma                  : 5.13.0
@prisma/client          : 5.13.0
Computed binaryTarget   : windows
Operating System        : win32
Architecture            : x64
Node.js                 : v20.10.0
Query Engine (Node-API) : libquery-engine b9a39a7ee606c28e3455d0fd60e78c3ba82b1a2b (at node_modules\@prisma\engines\query_engine-windows.dll.node)
Schema Engine           : schema-engine-cli b9a39a7ee606c28e3455d0fd60e78c3ba82b1a2b (at node_modules\@prisma\engines\schema-engine-windows.exe)
Schema Wasm             : @prisma/prisma-schema-wasm 5.13.0-23.b9a39a7ee606c28e3455d0fd60e78c3ba82b1a2b
Default Engines Hash    : b9a39a7ee606c28e3455d0fd60e78c3ba82b1a2b
Studio                  : 0.500.0

[ashlite]

After running the code, I'm confirm this is only typescript that throwing the error. While the resulting endpoint work normally.

[SevInf]

Hi @ashlite
In order for TS inference to work, we need a precise type for select parameters. Since your variables are annotated with generic ASelect and BSelect types this would be the type the variable would have. TS will not know about specific fields and values stored in there anymore, it will only know that it can be any value that select can accept. Therefore, inference for result types will no longer work.

To get what you try to achieve you need to remove type annotation and use as const modifier:

const selectB = {
  id: true,
  col1: true,
  col2: true,
  aData: {
    select: selectA
  }
} as const;

If you still want make sure it's valid SelectB input while also preserving the exact type, you can combine that with satisfies operator:

const selectB = {
  id: true,
  col1: true,
  col2: true,
  aData: {
    select: selectA
  }
} as const satisfies Prisma.BSelect;

[ashlite]

ahh I see
thank you for the heads-up.