import type {Except} from './except'; import type {HomomorphicPick} from './internal'; import type {KeysOfUnion} from './keys-of-union'; import type {Simplify} from './simplify'; /** 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 type {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. // } ``` @category Object */ export type SetOptional<BaseType, Keys extends keyof BaseType> = BaseType extends unknown // To distribute `BaseType` when it's a union type. ? Simplify< // Pick just the keys that are readonly from the base type. Except<BaseType, Keys> & // Pick the keys that should be mutable from the base type and make them mutable. Partial<HomomorphicPick<BaseType, Keys & KeysOfUnion<BaseType>>> > : never;