1/**
2Create a type that makes the given keys optional. The remaining keys are kept as is. The sister of the `SetRequired` type.
3
4Use-case: You want to define a single model where the only thing that changes is whether or not some of the keys are optional.
5
6@example
7```
8import {SetOptional} from 'type-fest';
9
10type Foo = {
11	a: number;
12	b?: string;
13	c: boolean;
14}
15
16type SomeOptional = SetOptional<Foo, 'b' | 'c'>;
17// type SomeOptional = {
18// 	a: number;
19// 	b?: string; // Was already optional and still is.
20// 	c?: boolean; // Is now optional.
21// }
22```
23*/
24export type SetOptional<BaseType, Keys extends keyof BaseType = keyof BaseType> =
25	// Pick just the keys that are not optional from the base type.
26	Pick<BaseType, Exclude<keyof BaseType, Keys>> &
27	// Pick the keys that should be optional from the base type and make them optional.
28	Partial<Pick<BaseType, Keys>> extends
29	// If `InferredType` extends the previous, then for each key, use the inferred type key.
30	infer InferredType
31		? {[KeyType in keyof InferredType]: InferredType[KeyType]}
32		: never;
33