Help with Path* methods

[millsp]

Help with Path* methods

[millsp]

Wow this is a crazy quest you've started! (Personally, I use Ramda (it's ok/well typed))

I doubt that anyone would be able to guess the proper ouput type as it's implementation-dependent.

But you could get a wider type though that is the return type of the iteratee as an array/list:
ReturnOf<Iteratee>[]

Where Iteratee is the generic type of the iteratee function that is passed to map.

And if you get this error it means that you're either doing something too complex or what I've explained over here

[regevbr]

@pirix-gh I'm not sure I follow...
The example I presented doesn't work as a standalone so it has nothing to do with overloading of the Iteratee ...

[millsp]

Then I am not sure of what you're doing. I never used underscore. I just saw that the docs specify the second argument but I see that you're passing an array? But I can't see this anywhere in the docs.

So I guess you're trying to do some kind of function type overload and some kind of selection?
If so, then you should write a mapped type that picks the right sub-elements. So it would map your first argument type then transform it (that's what mapped types are used for) with O.Pick

[regevbr]

The docs state vaguely (and the code backs it up) that iteratee value is actually passed to _.iteratee and then if you pass a string path array, it will be passed to _.property so my use case is valid.

But all of this has nothing to do with my problem, as the example above simply fails regardless of the other overloaded methods (which I can send here if you want)

It seems that the issue only happens because we pass an explicit array (instead of spread args)... Where in the following example it works good:

        mapE<T extends object, K extends string[]>(
            list: T[],
            ...iterator: A.Cast<K, O.PathValid<T, K>>): Array<U.Nullable<O.Path<T, K>>>;

_.map( [{arr: {arr2: [5, 1, 7]}}, {arr: {arr2: [5, 1, 7]}}], 'arr', 'arr2');

Can you tell why that happens?

[regevbr]

The following example does work with the original code (no spread).
It seems that it is related to how Typescript realizes the type of the array.

_.map( [{arr: {arr2: [5, 1, 7]}}, {arr: {arr2: [5, 1, 7]}}], ['arr', 'arr2'] as ['arr', 'arr2']);

One can try to use

_.map( [{arr: {arr2: [5, 1, 7]}}, {arr: {arr2: [5, 1, 7]}}], ['arr', 'arr2'] as const);

But then the array becomes readonly and can't be passed into your library types...

[millsp]

You can, use T.Writable before passing it to other types. Sorry that I can't help you more atm. I am very busy.

[regevbr]

That works!
Writable of Tuple is not exported - I will open a bug for it.