Except

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

type Foo = {
	a: number;
	b: string;
};

type FooWithoutA = Except<Foo, 'a'>;
//=> {b: string}

// @ts-expect-error
const fooWithoutA: FooWithoutA = {a: 1, b: '2'};
// errors: 'a' does not exist in type '{ b: string; }'

type FooWithoutB = Except<Foo, 'b', {requireExactProps: true}>;
//=> {a: number} & Partial<Record<'b', never>>

// @ts-expect-error
const fooWithoutB: FooWithoutB = {a: 1, b: '2'};
// errors at 'b': Type 'string' is not assignable to type 'undefined'.

// The `Omit` utility type doesn't work when omitting specific keys from objects containing index signatures.

// Consider the following example:

type UserData = {
	[metadata: string]: string;
	email: string;
	name: string;
	role: 'admin' | 'user';
};

// `Omit` clearly doesn't behave as expected in this case:
type PostPayload = Omit<UserData, 'email'>;
//=> {[x: string]: string; [x: number]: string}

// In situations like this, `Except` works better.
// It simply removes the `email` key while preserving all the other keys.
type PostPayloadFixed = Except<UserData, 'email'>;
//=> {[x: string]: string; name: string; role: 'admin' | 'user'}

 Object