Type signature for TestModule.get() is too restrictive

[michaelbromley]

I'm submitting a...

[ ] Regression 
[ ] 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

In a spec file:

let productService: ProductService;
let connection: MockConnection;

beforeEach(async () => {
    const module = await Test.createTestingModule({
        providers: [
            ProductService,
            { provide: Connection, useClass: MockConnection },
        ],
    }).compile();

    productService = module.get(ProductService);
    connection = module.get<MockConnection>(Connection); // <-- Error: Type 'Connection' is not assignable to type 'MockConnection'.    
});

Expected behavior

I would expect that I could explicitly set the generic argument as MockConnection without error.

Minimal reproduction of the problem with instructions

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

I want to get a reference to the mocked connection instance without resorting to casting to any.

For a comparison, Angular's TestBed.get() is typed with token: any, which I feel is too loose. I like the fact that in Nest, the type is inferred with a generic arg, but for testing, where mocks are the norm, this seems too strict.

I would suggest implementing a slightly looser definition of get() (simply adding Type<any> to the union) on the TestingModule class, like this:

export class TestingModule extends NestApplicationContext {
    // ...
   get<T>(typeOrToken: Type<T> | Type<any> | string | symbol, options?: { strict: boolean; }): T {
       return super.get(typeOrToken, options);
   }
}

This would allow both patterns to work:

module.get(Connection); // correctly infers return type Connection
module.get<MockConnection>(Connection); // returns type MockConnection

If you think this would make sense to add, I would happy to submit this as a pull request. I am building something on top of Nest and I'd be happy to contribute back to this excellent project!

Environment

Nest version: 5.0.1

[kamilmysliwiec]

Fixed in v5.1.0

[lock]

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