g-makarov / dot-path-value Goto Github PK

What – Wrong type for optional paths
Expected – string | undefined
Actual – string

Example

import {getByPath} from 'dot-path-value';

import { Equal, Expect } from "@type-challenges/utils";

type AuthorDetails = {
  author?: {
    location?: {
      city: string;
    };
  };
};

const obj: AuthorDetails = {
  author: {
    location: {
      city: "London"
    }
  },
};

const authorLocationCity = getByPath(obj, "author.location.city");

type cases = [
  // ✅ optional path
  Expect<Equal<typeof authorLocationCity, string | undefined>>,
];

TS Playground – https://tsplay.dev/WJ7e6w

The issue

Given the following code:

import { getByPath } from 'dot-path-value';

type Recursive = {
  a: string;
  r: Recursive;
};

function x(type: Recursive) {
  getByPath(type, '');
  ~~~~~~~~~~~~
}

we get the following error:

Type of property 'r' circularly references itself in mapped type
'{ [K in //keyof Recursive]-?: PathConcat<K & string, Recursive[K]>; }'.(2615)

which makes sense why it would not print until infinity (or at the max TS iterations).

See reproduction

Suggestion

Don't try to infer the fields of the recursive type, or allow inference for only one level deep.

BTW, really cool library, thanks for sharing 🙂

I am using getByPath in a helper function and passing in a Path<T> as a parameter. The path is useful to me in another package, which takes an array rather than a "dotted" path. However, attempting path.split('.') throws up a Property 'split' does not exist on type 'Path<T>' typescript error.

function takesPathAsArray(path: string[]) {
  // does something fancy with the path
}

function helperFn<T>(obj: T, path: Path<T>) {
  const value = getByPath(obj, path);

  // error is here                       v v v v v v v v 
  const somethingElse = takesPathAsArray(path.split('.'));
}

I can of course cast path as a string there, but I was wondering if there was a way for the library to support it?

Hi,

Thanks for the library. It would be great if it provided an hasByPath() method to check the path's availability.

Thanks,

Hello, g-makarov

I think I found vulnerability in this package. Where can I send this report??

It seems that Path doesn't pick out object keys which are numbers, rather than strings. For example:

const obj = {
  days: {
    1: true,
    "2": false,
    3: true
  }
}

type PathObj = Path<typeof obj>;
//    ^? type PathObj = 'days' | 'days.2'

Example playground for reference

const obj = {
  a: {
    b: [
      {
        c: 1,
      },
    ],
  },
}
getPath(obj, a.b[0].c) // 1

js is easy, safe type is too difficult 😅.

export function getByPath(
  obj,
  path,
) {
  return path
    .replace(/\[([^\[\]]*)\]/g, '.$1.')
    .split('.')
    .filter(t => t !== '')
    .reduce((prev, cur) => prev && prev[cur], obj)
}

Hi,

It seems that passing a generic which extends something does not correctly resolve at least the extended options:

Reproduction: https://tsplay.dev/NaEx9N

Firstly, tremendous typescript expertise on offer here. Lots to learn from.

I was wondering how you might feel about a PR for a setByPath function? I have knocked up a basic one locally using your existing getByPath function.

Let me know and I will put one together!

The type of the item accessed is a union of all the types of the items in the array:

const obj = {
    a: {
        b: [
            {
                c: 1,
            },
            'test',
            true
        ],
    },
};

const value = getByPath(obj, 'a.b.1');

In this case the type of value is string | boolean | { c: number; } where it should be string