ts-jest regression in 1.0.0 due to DeepMocked type changes

.github/workflows/ci.yml

@@ -38,7 +38,6 @@ jobs:
         uses: pnpm/action-setup@v4
         with:
           version: 10
-          cache: true
 
       - name: Use Node.js ${{ matrix.node-version }}
         uses: actions/setup-node@v4

packages/testing/ts-jest/package.json

@@ -38,9 +38,11 @@
     "access": "public"
   },
   "devDependencies": {
+    "@aws-sdk/client-s3": "^3.962.0",
     "@jest/globals": "^27.4.3",
     "jest": "^27.4.3",
-    "jest-mock": "27.5.1"
+    "jest-mock": "27.5.1",
+    "typeorm": "^0.3.28"
   },
   "jest": {
     "moduleFileExtensions": [

packages/testing/ts-jest/src/mocks.spec.ts

@@ -1,7 +1,9 @@
 import { ExecutionContext } from '@nestjs/common';
 import { HttpArgumentsHost } from '@nestjs/common/interfaces';
 import { Test, TestingModule } from '@nestjs/testing';
+import { S3Client } from '@aws-sdk/client-s3';
 import { createMock, DeepMocked } from './mocks';
+import { Repository } from 'typeorm';
 
 interface TestInterface {
   someNum: number;
@@ -222,6 +224,19 @@ describe('Mocks', () => {
       expect(result).toBe(true);
     });
 
+    it('should handle real AWS SDK S3Client without type instantiation errors', () => {
+      // This is the real-world case that triggers TS2589 with the current DeepMocked implementation
+      const s3Client: S3Client = createMock<S3Client>();
+      expect(s3Client).toBeDefined();
+    });
+
+    it('should handle real TypeORM Repository without too complex of a type errors', () => {
+      // This is the real-world case that triggers TS2590: with the current DeepMocked implementation
+      const repo: Repository<{ a: number }> =
+        createMock<Repository<{ a: number }>>();
+      expect(repo).toBeDefined();
+    });
+
     it('should work with classes having nested properties', () => {
       const mock = createMock<TestClass>();
       mock.nested.someOtherMethod.mockReturnValueOnce(99);

packages/testing/ts-jest/src/mocks.ts

@@ -1,3 +1,4 @@
+/* eslint-disable @typescript-eslint/no-empty-object-type */
 import { jest } from '@jest/globals';
 import { Mock } from 'jest-mock';
 
@@ -17,11 +18,23 @@ export type PartialFuncReturn<T> = {
     : DeepPartial<T[K]>;
 };
 
+type IsExactlyUnknown<T> = unknown extends T
+  ? T extends {}
+    ? false
+    : true
+  : false;
+
 export type DeepMocked<T> = {
-  [K in keyof T]: Required<T>[K] extends (...args: any[]) => infer U
-    ? jest.MockInstance<ReturnType<Required<T>[K]>, jest.ArgsType<T[K]>> &
-        ((...args: jest.ArgsType<T[K]>) => DeepMocked<U>)
-    : DeepMocked<T[K]>;
+  [K in keyof T]: IsExactlyUnknown<T[K]> extends true
+    ? any
+    : NonNullable<T[K]> extends (...args: any[]) => infer U
+      ? jest.MockInstance<ReturnType<NonNullable<T[K]>>, jest.ArgsType<T[K]>> &
+          ((...args: jest.ArgsType<T[K]>) => DeepMocked<U>)
+      : NonNullable<T[K]> extends object
+        ? undefined extends T[K]
+          ? DeepMocked<NonNullable<T[K]>> | undefined
+          : DeepMocked<T[K]>
+        : T[K];
 } & T;
 
 const jestFnProps = new Set([