Support for dynamic mocking frameworks

I’m submitting a…

[ ] Regression 
[X] Bug report
[X] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead post your question on Stack Overflow.

Current behavior

When running e2e tests, app.init() throws the following the following exception if I override a provider with a dynamic mock.

    TypeError: instance.onModuleInit is not a function

      at MapIterator.Promise.all.iterare_1.default.map.filter.filter.map [as iteratee] (../node_modules/@nestjs/core/nest-application-context.js:64:47)
      at MapIterator.next (../node_modules/iterare/src/map.ts:11:39)
      at IteratorWithOperators.next (../node_modules/iterare/src/iterate.ts:21:28)
          at Function.all (<anonymous>)
      at NestApplication.callModuleInitHook (../node_modules/@nestjs/core/nest-application-context.js:60:23)
      at NestApplication.callInitHook (../node_modules/@nestjs/core/nest-application-context.js:51:24)
      at NestApplication.init (../node_modules/@nestjs/core/nest-application.js:96:20)

Expected behavior

The ablity to override providers with dynamic mocks.

Minimal reproduction of the problem with instructions

Just to establish some context…

• the mocking api is ts-mockito
• the exists method on the PageService is used by the controllers to determine if a page exists

describe('Page API', () => {
  let app: INestApplication;
  const mockPageService: PageService = mock(PageService);

  beforeAll(async () => {
    const mod = await Test.createTestingModule({
      imports: [PagesModule],
    })
      .overrideProvider(PageService)
      .useValue(instance(mockPageService))
      .compile();

    app = mod.createNestApplication();
    await app.init();  // <---- exception is thrown here
  });

  it('[GET] /pages', () => {
    return request(app.getHttpServer())
      .get('/pages')
      .expect(200);
  });

  describe('[GET] /pages/:slug', () => {
    beforeAll(() => {
      when(mockPageService.exists('non-existent-page')).thenReturn(false);
      when(mockPageService.exists('example-page')).thenReturn(true);
    });
    it('should return 4o4 when :slug cannot be found', () => {
      return request(app.getHttpServer())
        .get('/pages/non-existent-page')
        .expect(404);
    });

    it('should return 200 when :slug can be found', () => {
      return request(app.getHttpServer())
        .get('/pages/example-page')
        .expect(200);
    });
  });

  afterAll(async () => {
    await app.close();
  });
});

What is the motivation / use case for changing the behavior?

Dynamic mocks are awesome.

Environment

Nest version: 5.5.0

 
For Tooling issues:
- Node version: v8.11.1  
- Platform: Windows 10  

Others:

[yavivi]

The issue still remains. For further clarification, please see this branch of my repository.

Get same issue on nestjs 6.1.1

[BrunnerLivio]

I looked into it; it is actually a issue by Nest. In the following function we check whether instance.onModuleInit is undefined.

https://github.com/nestjs/nest/blob/baa20004fccca575336d7455a3a3e754400cc0e9/packages/core/hooks/on-module-init.hook.ts#L16-L18

But (probably) due to the mocking library, instance.onModuleInit is null, therefore hasOnModuleInitHook returns true.

Changing it to return !isNil((instance as OnModuleInit).onModuleInit); will fix this issue.

Thanks a lot for your repository @nrhoffmann, it allowed me to get to the root cause of this issue quickly ! Sorry for your inconveniences and closing this issue. We review a lot of issues, so every now and then an issue gets closed, which should not have been 😃