type-fest/source/set-required.d.ts

import type {Except} from './except';
import type {Simplify} from './simplify';

/**
Create a type that makes the given keys required. The remaining keys are kept as is. The sister of the `SetOptional` type.

Use-case: You want to define a single model where the only thing that changes is whether or not some of the keys are required.

@example
```
import type {SetRequired} from 'type-fest';

type Foo = {
	a?: number;
	b: string;
	c?: boolean;
}

type SomeRequired = SetRequired<Foo, 'b' | 'c'>;
// type SomeRequired = {
// 	a?: number;
// 	b: string; // Was already required and still is.
// 	c: boolean; // Is now required.
// }
```

@category Object
*/
export type SetRequired<BaseType, Keys extends keyof BaseType> =
	// `extends unknown` is always going to be the case and is used to convert any
	// union into a [distributive conditional
	// type](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-8.html#distributive-conditional-types).
	BaseType extends unknown
		? Simplify<
		// Pick just the keys that are optional from the base type.
		Except<BaseType, Keys> &
		// Pick the keys that should be required from the base type and make them required.
		Required<Pick<BaseType, Keys>>
		>
		: never;