Ts-toolbelt: Pick two different branch of an object that have different subobject names

[mifozski]

🤔 Question

Describe your question

How do I pick two different paths of an object that have different subobject names, for example:

interface Test {
  foo: {
    foofoo: string;
  };
  bar: number;
  unneeded: null;
}

type pickedTest = O.P.Pick<Test, ['foo' | 'bar', 'foofoo']>;

I want pickedTest to be

type pickedTest = {
  foo: {
    foofoo: string;
  };
  bar: number;
}

but the resulting type is

type pickedTest = {
  foo: {
    foofoo: string;
  };
}

which kinda makes sense.
What is the expected syntax here and if that's even possible?

[millsp]

Hi @mifozski,

By default, it does not include something that does not have a valid path.
However, we could write another version called PickAll that would solve your use case:

Imagine the following scenario:

interface Test {
  foo: {
    foofoo: string;
    barbar: string
  };
  bar: {
    foofoo: {
      barbar: string
      yogyog: string
    }
  };
  unneeded: null;
}

type pickedTest = PickAll<Test, ['foo' | 'bar', 'foofoo', 'barbar']>;

and the ouput type would be:

type pickedTest = {
    foo: {
        foofoo: string;
    };
    bar: {
        foofoo: {
            barbar: string;
        };
    };
}

Is it what you need? If so, do you find the name convenient (do you have a better idea)?
PickLazy, PickTry, PickAll. The name must start with Pick, as it's my convention.

So the type just picks whatever it can, trying as it dives.

[millsp]

Maybe I could make it the default behavior... Have to think about it.

[ctrlplusb]

Strangely enough I was trying to solve the exact some problem in my library. 😀

[millsp]

Must be really useful then!

@ctrlplusb what do you think? Should I make this the default behavior?

[mifozski]

I think it makes sense to make it a default behavior as I can't think of a case where we'd want to pick several paths at first and then narrow it down to something that will be valid only for one path.

[ctrlplusb]

Yep, I agree, I thought this would have been the default behaviour too. :)

[millsp]

Well, thanks, closing the debate. I agree that it is inconsistent. Working on it.

[millsp]

@mifozski @ctrlplusb, it's out ! :timer_clock:

Thanks for reporting this bug

[ctrlplusb]

Woot! Gonna experiment with this soon. 🎉

[millsp]

I must say, this was quite a challenging type to write. I am still wondering if it could be simplified :thinking: