`path` methods typing

[wclr]

So what about path (assocPath, etc) methods typings?

Maybe type them for most common cases like string props, and up to 3-4 path length?

[KiaraGrouwstra]

I was just about to link to the thread at TS, then realized you were the OP there. :)

[wclr]

But if I'm not mistaken it works well for basic cases [string, string, string], the only problem is just with the size of signature needed, no? As I said just add common case for 3-4 length string tupple.

[KiaraGrouwstra]

Hm, @ikatyang said those were still in... weird.

[ikatyang]

I didn't touch the path typings, they should still remain the same ( source -> dist ).

[wclr]

Hm I thought path could be typed in basic cases, but for now I see I doen't even work for basic things) Is something.

[ikatyang]

We do not support the 1-length tuple version since it's a special case that tuples with any length can be all considered 1-length tuple, it's the super type of any tuple.

---

@tycho01, It seems we did not support path with excess property originally?

R.path(['a', 'c'], { a: { c: 1 } }); //=> number
R.path(['a', 'c'], { a: { c: 1 }, b: 2 }); //=> {}

[KiaraGrouwstra]

We do not support the 1-length tuple version since it's a special case that tuples with any length can be all considered 1-length tuple, it's the super type of any tuple.

Uhh. afaik there are no special cases, it sees length 2 tuples as super types of length 3+ tuples too. That could be addressed by just putting higher length options first I guess.

It seems we did not support path with excess property originally?

Hm... if it messed up on that I imagine it could be addressed by ensuring we'd match using objects containing a string index as well, e.g. { k: V } & { [K: string]: any }.

[ikatyang]

The & { [X: string]: any } thing seems not working:

declare function path2<T1 extends string, T2 extends string, TResult>(path: [T1, T2], obj: {
    [K1 in T1]: {
        [K2 in T2]: TResult;
    };
}): TResult;

declare function path2withAny<T1 extends string, T2 extends string, TResult>(path: [T1, T2], obj: {
    [K1 in T1]: {
        [K2 in T2]: TResult;
    } & {
        [X: string]: any;
    };
} & {
    [X: string]: any;
}): TResult;

path2(["a", "b"], { a: { b: 1 }}); //=> 1
path2(["a", "b"], { a: { b: 1 }, c: 2 });
/*                ^^^^^^^^^^^^^^^^^^^^^
[ts]
Argument of type '{ a: { b: number; }; c: number; }' is not assignable to parameter of type '{ a: { b: ((radix?: number) => string) | (() => number) | ((locales?: string | string[], options?...'.
  Types of property 'a' are incompatible.
    Type '{ b: number; }' is not assignable to type '{ b: ((radix?: number) => string) | (() => number) | ((locales?: string | string[], options?: Num...'.
      Types of property 'b' are incompatible.
        Type 'number' is not assignable to type '((radix?: number) => string) | (() => number) | ((locales?: string | string[], options?: NumberFo...'.
*/
path2withAny(["a", "b"], { a: { b: 1 }}); //=> 1
path2withAny(["a", "b"], { a: { b: 1 }, c: 2 });
/*                       ^^^^^^^^^^^^^^^^^^^^^
[ts]
Argument of type '{ a: { b: number; }; c: number; }' is not assignable to parameter of type '{ a: { b: ((radix?: number) => string) | (() => number) | ((locales?: string | string[], options?...'.
  Type '{ a: { b: number; }; c: number; }' is not assignable to type '{ a: { b: ((radix?: number) => string) | (() => number) | ((locales?: string | string[], options?...'.
    Types of property 'a' are incompatible.
      Type '{ b: number; }' is not assignable to type '{ b: ((radix?: number) => string) | (() => number) | ((locales?: string | string[], options?: Num...'.
        Type '{ b: number; }' is not assignable to type '{ b: ((radix?: number) => string) | (() => number) | ((locales?: string | string[], options?: Num...'.
          Types of property 'b' are incompatible.
            Type 'number' is not assignable to type '((radix?: number) => string) | (() => number) | ((locales?: string | string[], options?: NumberFo...'.
*/

[clark0x]

[ikatyang]

@clarkorz It seems you're not using our type:

If you're using our type, can you open another issue with steps to reproduce?

[goodmind]

@tycho01 what you think about this?

https://flow.org/try/#0CYUwxgNghgTiAEAzArgOzAFwJYHtX1BAAcBlEARwB4AFAPgAoAoeeAOnaKgwAsAueaowCU-ACQAVZEQggAslCI0ANPEriV1GDiIMiWov03ah8ALy144sxdEBRGQFsQqDOICeREGo37atRsws8IygkLAIAG6w8ERYnmIAwjgORDgAziAASiARIDAZAWB4aRjwGLAA5iAY-ADk5TBVGLVm8PWV1bWFxaUgAB5QKTKtAN6BiDg4-GNB8ABGsNOBs1EQyCBLs7OoICUgwPwNTUrLQQC+pxcsF1dBjEWoJfB7RACMrbGe9OyshKQUTBYtQmOFqJyBCxgYMCtVW6y6QiE9H6g2kICE3UepReACYPnEQN92H8yORAW0dntgAikS9XhjGABueh06bwSkYfZ1I6deBnBkAegAVMwhfA7H1PJhbDAtDBRc8MDAsKgKvAIFhOTAoBB4AADHkYPWsBXibhYNJlDwIC3wFVFFJcLBzYYAd013HZyAcczyooFTJZnKIOP4qG9vpgGKAA
https://gist.github.com/zerobias/6e49651079d23f173f95ecc49b6a6ee1

[KiaraGrouwstra]

For posterity,

the 1-length tuple [is] the super type of any tuple

This is fixed since microsoft/TypeScript#17765.

@goodmind:

So, I haven't paid attention to Flow in a while, notably because the timing I entered front-end engineering got me on the Angular / TS path. But honestly, that looks great.

What I'm getting from this example, and a subsequent glimpse at their docs:

• no erasure (edit: ?)
• composition ($ComposeReverse, $Compose)
• heterogeneous map ($TupleMap, $ObjMap)
• type calls ($Call)

These are the exact game-changers essential for FP I've been clamoring for in TS for ages, and I suppose it only makes sense FB's team behind React and Immutable.js would ensure to get them in.

I guess this goes to show competition is great. I'd seriously consider retrying Flow if I were to try front-end again. Being able to use FP abstractions without having to fight the type system just might make it enjoyable again. :)

[KiaraGrouwstra]

@goodmind: curious to figure out how Flow would fare, I tried a bit to see if I could port my type lib to it in a new branch, WIP. Thoughts:

• I've yet to figure out an equivalent for TS's in, which I used there to make object types from generic keys ({ [P in K]: 1 }, the type equivalent of dynamic JS keys like { [k]: 1 }).
• Not sure how to properly test this yet. Try Flow 404s on a few JS assets, IDE plugins often just seem to hang for me (like for TS). I'm having trouble figuring out the result types -- there doesn't seem to be an equivalent to TS's .d.ts output files, nor to the TS Compiler API we used for type tests at typical.

Guess I'm still pretty new to it, so not quite sure where to look or who to ask yet.

@ikatyang your Jest testing method wasn't taken from a Flow equivalent either, right?

[ikatyang]

I'm not sure what do you mean the testing method, but I didn't use Flow before so it shouldn't be.