spyOn(...).mockImplementation should return a SpyInstance rather than a Mock

[jamiecopeland]

• I tried using the @types/jest package and had problems.
• I tried using the latest stable version of tsc. https://www.npmjs.com/package/typescript
• I have a question that is inappropriate for StackOverflow. (Please ask any appropriate questions there).
• @alexjoverm @asvetliakov @NoHomey @orta

While attempting to write a system to un-mock/un-spy on modules I came across what seems to be a problem with types returned by mockImplementation (and mockImplementationOnce, mockReturnThis, mockReturnValue, mockReturnValueOnce) as a result of calling spyOn. This is that while the typings specify that mockImplementation returns a Mock, what actually comes back is a SpyInstance with the mockRestore function available to call. It'd be great to get some feedback on this, and if you think it's a valid fix, I can get a PR put together reflecting this change.

The type hack version below works, even though the current types specify that it shouldn't

// Spy creating/cleaning utility (as it should be)
const createSpies = (spies: jest.SpyInstance<any>[]) => () => spies.forEach(spy => spy.mockRestore());

// Spy creating/cleaning utility (with hack to prevent compiler from complaining)
const createSpies = (spies: any[]) => () => spies.forEach(spy => spy.mockRestore());

// Test
it('should...', () => {
  const restoreMocks = createSpies([
    jest.spyOn(moduleA, 'sayHi').mockImplementation(() => 'mock hello')
    jest.spyOn(moduleB, 'sayBye').mockImplementationOnce(() => 'mock goodbye')
  ]);

  // Do tests...

  restoreMocks();
});

[duro]

We need this! @alexjoverm @asvetliakov @NoHomey @orta

Can we get an update, they types haven't been updated in over a month

[diofeher]

+1 on that

[vkrol]

Is this still an issue? I don't think so. The example from the first message in this thread is working without type errors. You can try it: https://github.com/vkrol/typescript-jest-spy-on-playground
Steps:

1. Clone the repository
2. Run the following commands:
   yarn
yarn typecheck

[orta]

Is this needed now that there's been some pretty massive refactoring in
#32579 (comment) and #32816 also ?

[orta]

Hi thread, we're moving DefinitelyTyped to use GitHub Discussions for conversations the @types modules in DefinitelyTyped.

To help with the transition, we're closing all issues which haven't had activity in the last 6 months, which includes this issue. If you think closing this issue is a mistake, please pop into the TypeScript Community Discord and mention the issue in the definitely-typed channel.