New Type: AllUnionFields (similar to SharedUnionFields)

[RebeccaStevens]

Type description + examples

Expand on SharedUnionFields with a type that keeps all the union fields.
This is a simplified version of #386.

This new type will simply change non-shared fields to optional with value unknown. Or with an option (proposed name exact), will be changed to be optional with a value of the union of all values for that property within the union.

Edit: This new type will change each field to be optional with a value of the union of all values for that property within the union.

Simple example by modifying the SharedUnionFields's example (probably not that great an example of why you'd actually want to use this type)

import type {AllUnionFields} from 'type-fest';

type Cat = {
	name: string;
	type: 'cat';
	catType: string;
};

type Dog = {
	name: string;
	type: 'dog';
	dogType: string;
};

function displayPetInfo(petInfo: Cat | Dog) {
	// typeof petInfo =>
	// {
	// 	name: string;
	// 	type: 'cat';
	// 	catType: string;
	// } | {
	// 	name: string;
	// 	type: 'dog';
	// 	dogType: string;
	// }

	console.log('name: ', petInfo.name);
	console.log('type: ', petInfo.type);

	// TypeScript complains about `catType` and `dogType` not existing on type `Cat | Dog`.
	console.log('animal type: ', petInfo.catType ?? petInfo.dogType);
}

function displayPetInfo(petInfo: AllUnionFields<Cat | Dog>) {
	// typeof petInfo =>
	// {
	// 	name: string;
	// 	type: 'cat' | 'dog';
	//  catType?: string;
	//  dogType?: string;
	// }

	console.log('name: ', petInfo.name);
	console.log('type: ', petInfo.type);

	// No TypeScript error.
	console.log('animal type: ', petInfo.catType ?? petInfo.dogType);
}

Type source

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[Emiyaaaaa]

I think this result is better (don't need a option to choose unknown or exact type):

type petinfo = {
 name: string;
 type: 'cat' | 'dog';
 catType?: string;
 dogType?: string;
}

I'm not sure if I'm missing it, I don't find the similar type in type-fest, I think it's a useful type (need a better type name).

[RebeccaStevens]

After thinking about this a bit more, I think I was being overly cautious with the exact option opt-in. I think that should probably be just the way it works.