Exact not function correctly with Dates since last commit

[nlynzaad]

Hi,

First off, I'm a new user of the project and just want to say thanks for your efforts in maintaining this exceptionally handy project.

Was struggling to get the Exact type to work and it seems to be related to a change that was made in commit #902, specifically the change from object to JsonObject. When having a date field, the validation does not throw an error as expected. The error however does appear in the version prior to the commit and in the new version if the Date field is removed.

import type {Exact, IsEqual, JsonObject} from "type-fest";
import type {ArrayElement} from "type-fest/source/internal";
import type {TagContainer} from "type-fest/source/opaque";
import {ExactObject} from "type-fest/source/exact";

type UserType = {
	id: string,
	name: string,
	createdAt: Date,
	email?: string,
};

type UserTypeWithoutDate = {
	id: string,
	name: string,
	email?: string | undefined,
};

const testValues = {
	id: 'asd',
	name: 'John',
	createdAt: new Date(),
	email: undefined,
	surname: 'Doe',
};

const testValuesWithoutDate = {
	id: 'asd',
	name: 'John',
	email: undefined,
	surname: 'Doe',
};

export type Exact_OLD<ParameterType, InputType> =
	IsEqual<ParameterType, InputType> extends true ? ParameterType
		// Convert union of array to array of union: A[] & B[] => (A & B)[]
		: ParameterType extends unknown[] ? Array<Exact<ArrayElement<ParameterType>, ArrayElement<InputType>>>
			// In TypeScript, Array is a subtype of ReadonlyArray, so always test Array before ReadonlyArray.
			: ParameterType extends readonly unknown[] ? ReadonlyArray<Exact<ArrayElement<ParameterType>, ArrayElement<InputType>>>
				// Leave tagged types as-is. We could try to make the untagged part Exact, and just leave the tag as-is, but that seems to create instanitation excessively deep errors.
				: ParameterType extends TagContainer<unknown> ? ParameterType
					: ParameterType extends object ? ExactObject<ParameterType, InputType>
						: ParameterType;

export type Exact_NEW<ParameterType, InputType> =
	IsEqual<ParameterType, InputType> extends true ? ParameterType
		// Convert union of array to array of union: A[] & B[] => (A & B)[]
		: ParameterType extends unknown[] ? Array<Exact<ArrayElement<ParameterType>, ArrayElement<InputType>>>
			// In TypeScript, Array is a subtype of ReadonlyArray, so always test Array before ReadonlyArray.
			: ParameterType extends readonly unknown[] ? ReadonlyArray<Exact<ArrayElement<ParameterType>, ArrayElement<InputType>>>
				// Only apply Exact for pure object types. For types from a class, leave it unchanged to TypeScript to handle.
				: ParameterType extends JsonObject ? ExactObject<ParameterType, InputType>
					: ParameterType;

function oldExactFunc <T extends Exact_OLD<UserType, T>>(user: T) {
	return user
}

function newExactFunc <T extends Exact_NEW<UserType, T>>(user: T) {
	return user
}

function newExactFuncWithoutDate <T extends Exact_NEW<UserTypeWithoutDate, T>>(user: T) {
	return user
}
const oldExactResult = oldExactFunc(testValues) //this errors correctly
const newExactResult = newExactFunc(testValues) //this does not error.
const newExactResultWithoutDate = newExactFuncWithoutDate(testValuesWithoutDate) //this errors correctly.

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[sindresorhus]

// @zorji

[zorji]

Hi @nlynzaad

I am trying to reproduce the issue but I can't in my IDE. Just want to clarify this with you, are you expecting the Exact type to throw error because surname is the excess field? I also noticed that email should be reported as well as the type does not allow undefined but the field can be optional.

[nlynzaad]

Hi @zorji ,

Thanks for looking into this.

Yes I'm expecting it to fail due to the additional "surname" property. I usually work in webstorm where I picked this issue up, confirmed now with vscode the editor show it as well and tsc also only fails using EXACT_OLD or with no date field

[nlynzaad]

for testing I got EXACT_OLD from the pre-commit diff and EXACT_NEW from current master.

[nlynzaad]

I created a stackblitz with the issue: Exact Issue

[zorji]

@nlynzaad Thanks I can reproduce it when using a variable. Let me see if I can provide a fix.

[zorji]

I drafted this fix #911

Do you mind help test if that fixes the issue for you?

[nlynzaad]

@zorji Thanks a lot.

I copied the draft into the larger project and worked as intended