fix: Emit single with Prisma type

src/handlers/emit-single.ts

@@ -1,4 +1,5 @@
 import AwaitEventEmitter from 'await-event-emitter';
+import { partition } from 'lodash';
 import { PropertyDeclarationStructure } from 'ts-morph';
 
 import { DMMF } from '../types';
@@ -17,11 +18,12 @@ function classProperty(
 ) {
   const { location, isList, propertyType } = eventArguments;
   if (['inputObjectTypes', 'outputObjectTypes'].includes(location) && !isList) {
-    const types = propertyType.filter(t => t !== 'null');
-    property.type = types.map(t => `InstanceType<typeof ${t}>`).join(' | ');
-    if (types.length !== propertyType.length) {
-      // If null was removed
-      property.type += ' | null';
-    }
+    const [safeTypes, instanceofTypes] = partition(
+      propertyType,
+      t => t === 'null' || t.startsWith('Prisma.'),
+    );
+    const mappedInstanceofTypes = instanceofTypes.map(t => `InstanceType<typeof ${t}>`);
+
+    property.type = [...mappedInstanceofTypes, ...safeTypes].join(' | ');
   }
 }

src/test/generate.spec.ts

@@ -1531,6 +1531,25 @@ describe('emit single', () => {
         }));
       expect(types).toHaveLength(0);
     });
+
+    it('type started with Prisma should not be wrapped to instanceof', async () => {
+      const types = sourceFile
+        .getClasses()
+        .flatMap(c => c.getProperties().map(p => ({ c, p })))
+        .map(({ c, p }) => ({
+          c,
+          p,
+          propertyType: p.getStructure().type,
+        }))
+        .map(({ propertyType }) => String(propertyType))
+        .filter(
+          propertyType =>
+            propertyType.includes('Prisma.') &&
+            propertyType.startsWith('InstanceType<'),
+        );
+
+      expect(types).toHaveLength(0);
+    });
   });
 
   describe('emit single second gen', () => {