fix(client): make nested omit types work (#25900)

When we have nested `select` or `include`, TypeScript at some point
gives up remembering what keys `A` has exactly and discards the `omit`
for whatever reason. Re-adding the `omit` key at the point it happens
using the `A & { omit: A['omit'] }` hack makes TypeScript a little bit
less forgetful.

Closes: prisma/team-orm#1442
Fixes: #24835

Co-authored-by: Jacek Malec <malec@prisma.io>

packages/client/src/runtime/core/types/exported/Result.ts

@@ -73,7 +73,16 @@ export type GetFindResult<P extends OperationPayload, A, ClientOptions> =
               : K extends '_count'
                 ? Count<P['objects']>
                 : never
-    } & (A extends { include: any } & Record<string, unknown> ? DefaultSelection<P, A, ClientOptions> : unknown)
+    } & (
+      A extends { include: any } & Record<string, unknown>
+        // The `A & { omit: ['omit'] }` hack is necessary because otherwise, when we have nested `select` or `include`,
+        // TypeScript at some point gives up remembering what keys `A` has exactly and discards the `omit` for whatever
+        // reason. Splitting the top-level conditional type above into two separate branches and handling `select` and
+        // `include` separately so we don't need to use `A extends { include: any } & Record<string, unknown>` above in
+        // this branch here makes zero difference. Re-adding the `omit` key here makes TypeScript remember it.
+        ? DefaultSelection<P, A & { omit: A['omit'] }, ClientOptions>
+        : unknown
+    )
   : DefaultSelection<P, A, ClientOptions>
 
 // prettier-ignore
@@ -83,7 +92,7 @@ export type SelectablePayloadFields<K extends PropertyKey, O> =
 
 // prettier-ignore
 export type SelectField<P extends SelectablePayloadFields<any, any>, K extends PropertyKey> =
-  P extends { objects: Record<K, any> } 
+  P extends { objects: Record<K, any> }
   ? P['objects'][K]
   : P extends { composites: Record<K, any> }
     ? P['composites'][K]
@@ -99,7 +108,7 @@ export type DefaultSelection<Payload extends OperationPayload, Args = {}, Client
 
 // prettier-ignore
 export type UnwrapPayload<P> = {} extends P ? unknown : {
-  [K in keyof P]: 
+  [K in keyof P]:
     P[K] extends { scalars: infer S, composites: infer C }[]
     ? Array<S & UnwrapPayload<C>>
     : P[K] extends { scalars: infer S, composites: infer C } | null
@@ -131,7 +140,7 @@ export type GetBatchResult = { count: number }
 export type GetGroupByResult<P extends OperationPayload, A> =
   A extends { by: string[] }
   ? Array<GetAggregateResult<P, A> & { [K in A['by'][number]]: P['scalars'][K] }>
-  : A extends { by: string } 
+  : A extends { by: string }
     ? Array<GetAggregateResult<P, A> & { [K in A['by']]: P['scalars'][K]}>
     : {}[]
 

packages/client/tests/functional/24835-omit-error/_matrix.ts

@@ -0,0 +1,4 @@
+import { defineMatrix } from '../_utils/defineMatrix'
+import { allProviders } from '../_utils/providers'
+
+export default defineMatrix(() => [allProviders])

packages/client/tests/functional/24835-omit-error/prisma/_schema.ts

@@ -0,0 +1,41 @@
+import { idForProvider } from '../../_utils/idForProvider'
+import testMatrix from '../_matrix'
+
+export default testMatrix.setupSchema(({ provider }) => {
+  return /* Prisma */ `
+      generator client {
+        provider = "prisma-client-js"
+        previewFeatures = ["omitApi"]
+      }
+
+      datasource db {
+        provider = "${provider}"
+        url      = env("DATABASE_URI_${provider}")
+      }
+
+      model A {
+        id ${idForProvider(provider)}
+
+        model_b B[]
+      }
+
+      model B {
+        id ${idForProvider(provider)}
+
+        a_id String
+        a    A   @relation(fields: [a_id], references: [id])
+
+        private_field String
+
+        c_id String
+        c    C   @relation(fields: [c_id], references: [id])
+      }
+
+      model C {
+        id ${idForProvider(provider)}
+
+        public_field String
+        B            B[]
+      }
+      `
+})

packages/client/tests/functional/24835-omit-error/test.ts

@@ -0,0 +1,26 @@
+import testMatrix from './_matrix'
+// @ts-ignore
+import type { PrismaClient } from './node_modules/@prisma/client'
+
+declare let prisma: PrismaClient
+
+testMatrix.setupTestSuite(() => {
+  test('have omitted field as never', async () => {
+    const example = await prisma.a.findFirst({
+      include: {
+        model_b: {
+          include: {
+            c: true,
+          },
+          omit: {
+            private_field: true,
+          },
+        },
+      },
+      omit: { id: true },
+    })
+
+    // @ts-expect-error
+    example?.model_b[0].private_field
+  })
+})