Jest service mocks have wrong types

[DaSchTour]

I have some code that uses mocks and jest functions like mockReturnValue. For example like this

const fooService = spectator.inject(FooService);
fooService.someMethod.mockReturnValue({foo: 'bar'});

This worked fine but now suddenly I get typescript errors TS2339: Property 'mockReturnValue' does not exist on type '((key: string | null, location?: string | undefined) => Observable ) & CompatibleSpy'..

It looks like typescript doesn't use the jest typings but the jasmine version.

I'm not sure if that is an issue with my configuration, with a wrong version of jest or maybe caused by TypeScript 5. Did anybody else expect similar issues?

[DaSchTour]

I searched a bit deeper into this issue and it seams that this change 4fc8e24 is causing the problem.

When reverting to the previous version mocks are typed correctly.

This is obviously a bug #614

[chimurai]

It might seem to work...
If you revert the code and run yarn build; you'll get this build error:

projects/spectator/jest/src/lib/mock.ts:7:126 - error TS2344: Type 'R' does not satisfy the constraint 'FunctionLike'.

7 export type SpyObject<T> = BaseSpyObject<T> & { [P in keyof T]: T[P] & (T[P] extends (...args: any[]) => infer R ? jest.Mock<R> : T[P]) };
                                                                                                                               ~

  projects/spectator/jest/src/lib/mock.ts:7:112
    7 export type SpyObject<T> = BaseSpyObject<T> & { [P in keyof T]: T[P] & (T[P] extends (...args: any[]) => infer R ? jest.Mock<R> : T[P]) };
                                                                                                                     ~
    This type parameter might need an `extends FunctionLike` constraint.

Hope someone can help out to fix this type issue properly 🙏

[NetanelBasal]

@chimurai, could you please assist in resolving the issue or potentially reverting the changes? Unfortunately, I am currently pressed for time and unable to investigate the matter at the moment.

[DaSchTour]

Maybe one thing to add is, that when adding () so actually calling methods typescript shows the correct type.
But I really can't decode the current type to understand where the issue is. The type should reflect, that if it is a function the property itself has the mock and not the return of the function. Hope that makes sense.

[chimurai]

Created a PR with a fix: #615

Would be nice if @DaSchTour could verify the fix.