| /** |
| 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. |
| Pick<BaseType, Exclude<keyof 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; |