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