O.Compact broken in 6.13

[mesqueeb]

🐞 Bug Report

import { O } from 'ts-toolbelt'

export enum ACTIVE_LESSON_STUDENT_STATUS {
	NEEDS_HELP = "NEEDS_HELP",
}

export interface StudentMeta {
	statuses: ACTIVE_LESSON_STUDENT_STATUS[]
}

type MergedWithCompact = O.Compact<StudentMeta, [Partial<StudentMeta>], 'deep'>

// v6.12 ✅
// type MergedWithCompact = {
// 	statuses: ACTIVE_LESSON_STUDENT_STATUS[];
// }

// v6.13 ❌
// type MergedWithCompact = {
// 	statuses: {
// 			[x: number]: ACTIVE_LESSON_STUDENT_STATUS;
// 	};
// }

The 0.13 is breaking a lot of things in my libraries with ts-toolbelt as depedency.

Right now my solution is to hard-code the version to v0.12 in all my libraries & tools that use ts-toolbelt.

[millsp]

Looking into this

[millsp]

This is happening because the new Merge is able to merge lists too, the old one would just skip it. This was a huge issue for type safety. And the problem here is that I chose to set the merging default to ramda style, that means that lists are not preserved by default...

So if you enable lodash-merging style, you can do pretty amazing things!

type t0 = Merge<{
    a: number[]
    b: {a: 1}[]
    c: {a: [0]}
}, {
    a: string[]
    b: {b: 2}[]
    c: {a: [0, 1, 2]}
}, 'deep', 0>

// {
//     a: (string | number)[];
//     b: {
//         a: 1;
//         b: 2;
//     }[];
//     c: {
//         a: [0, 1, 2];
//     };
// }

Actually, I plan to make the lodash-merging style the default soon.

[mesqueeb]

@millsp
I'm all for positive change and increasing possibilities!

How do we enable "Lodash-merging style"? I've never used Lodash before. 😅

[millsp]

You just have to pass the 0 option like in the example. 1 for ramda.

[millsp]

Waiting for this to merge DefinitelyTyped/DefinitelyTyped#46213

[millsp]

The only thing to know when using lodash merging style is that when one of your fields is undefined, lodash will fill that gap when merging, that's not the case for ramda. Ramda instead checks if the key exists or not. So if you have a field that you explicitly set to undefined, ramda wont complete it when merging, lodash will.

[millsp]

Fixed!