fix: DeepPartial with generic parameter should allow assigning {}

[mpiniarski]

Description

DeepPartial supports the assignment of {} when the passed type is generic:

const result: DeepPartial<T> = {}

It's not possible to test with dts-jest, so I setup an additional tsconfig.test-d.json used to run tsc on src/**/*.test-d.ts files.
It would be even better to integrate types testing library like tsd, to be able to assert also cases when type error is expected.

Related issues:

• Resolved DeepPartial does not allow empty object for generics #183

Checklist

• I have read CONTRIBUTING.md
• I have linked all related issues above
• I have rebased my branch

For bugfixes:

• I have added at least one unit test to confirm the bug have been fixed
• I have checked and updated TOC and API Docs when necessary

[mpiniarski]

@piotrwitek can you take a look?
What do you think about tests?

[piotrwitek]

@mpiniarski thanks I'll tomorrow morning :)

[piotrwitek]

@mpiniarski could you please remove the package-lock file from the PR, it shouldn't be committed as it's unrelated

[piotrwitek]

@mpiniarski I think this test should look like this to reflect the original issue report, could you try it?

<T extends{}>() => {
    // @dts-jest:pass:snap -> I'm not sure about what type will be resulting here from dts as it's using generic
    // possibly ` DeepPartial<T>`, let me know we'll figure it out
    testType<DeepPartial<T>>({});
  };

In summary, whatever dts will derive and there is no error from the compiler on test assignments we can assume it's working correctly

[piotrwitek]

Hey @mpiniarski, have you seen my comments?

[mpiniarski]

Fixed, sorry for the delay.

[piotrwitek]

No problem, thanks a lot. I'll have a look shortly :)

[piotrwitek]

Now it looks exactly as in the ticket, nice :)

[piotrwitek]

Amazing work @mpiniarski thanks again :)