feat: enforce error when selecting only virtual fields in query

Author: genu

packages/orm/src/client/crud/operations/base.ts

@@ -322,6 +322,7 @@ export abstract class BaseOperationHandler<Schema extends SchemaDef> {
         parentAlias: string,
     ) {
         let result = query;
+        let hasNonVirtualField = false;
 
         for (const [field, payload] of Object.entries(selectOrInclude)) {
             if (!payload) {
@@ -330,6 +331,7 @@ export abstract class BaseOperationHandler<Schema extends SchemaDef> {
 
             if (field === '_count') {
                 result = this.buildCountSelection(result, model, parentAlias, payload);
+                hasNonVirtualField = true;
                 continue;
             }
 
@@ -338,6 +340,7 @@ export abstract class BaseOperationHandler<Schema extends SchemaDef> {
                 // scalar field - skip virtual fields as they're computed at runtime
                 if (!fieldDef.virtual) {
                     result = this.dialect.buildSelectField(result, model, parentAlias, field);
+                    hasNonVirtualField = true;
                 }
             } else {
                 if (!fieldDef.array && !fieldDef.optional && payload.where) {
@@ -355,9 +358,14 @@ export abstract class BaseOperationHandler<Schema extends SchemaDef> {
                     //  regular relation
                     result = this.dialect.buildRelationSelection(result, model, field, parentAlias, payload);
                 }
+                hasNonVirtualField = true;
             }
         }
 
+        if (!hasNonVirtualField) {
+            throw createInternalError('Cannot select only virtual fields', model);
+        }
+
         return result;
     }
 

tests/e2e/orm/client-api/virtual-fields.test.ts

@@ -157,6 +157,39 @@ model User {
         expect(virtualFieldCalled).toBe(false);
     });
 
+    it('throws error when selecting only virtual fields', async () => {
+        const db = await createTestClient(
+            `
+model User {
+    id Int @id @default(autoincrement())
+    firstName String
+    lastName String
+    fullName String @virtual
+}
+`,
+            {
+                virtualFields: {
+                    User: {
+                        fullName: (row: any) => `${row.firstName} ${row.lastName}`,
+                    },
+                },
+            } as any,
+        );
+
+        await db.user.create({
+            data: { id: 1, firstName: 'Alex', lastName: 'Smith' },
+            select: { id: true },
+        });
+
+        // Selecting only virtual fields should throw a clear error
+        await expect(
+            db.user.findUnique({
+                where: { id: 1 },
+                select: { fullName: true },
+            }),
+        ).rejects.toThrow(/cannot select only virtual fields/i);
+    });
+
     it('works with optional virtual fields', async () => {
         const db = await createTestClient(
             `