blob: 35398992b907e24123b98c724155d2dfc6d123a0 [file] [log] [blame]
import {Except} from './except';
/**
Create a type that makes the given keys optional. The remaining keys are kept as is. The sister of the `SetRequired` 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 optional.
@example
```
import {SetOptional} from 'type-fest';
type Foo = {
a: number;
b?: string;
c: boolean;
}
type SomeOptional = SetOptional<Foo, 'b' | 'c'>;
// type SomeOptional = {
// a: number;
// b?: string; // Was already optional and still is.
// c?: boolean; // Is now optional.
// }
```
*/
export type SetOptional<BaseType, Keys extends keyof BaseType = keyof BaseType> =
// Pick just the keys that are not optional from the base type.
Except<BaseType, Keys> &
// Pick the keys that should be optional from the base type and make them optional.
Partial<Pick<BaseType, Keys>> extends
// If `InferredType` extends the previous, then for each key, use the inferred type key.
infer InferredType
? {[KeyType in keyof InferredType]: InferredType[KeyType]}
: never;