Recursive Partial<T> in TypeScript

Question

I have this interface:

export interface UserSettings {     one: {         three: number;         four: number;     };     two: {         five: number;         six: number;     }; } 

...and want to turn it into this:

export interface UserSettingsForUpdate {     one?: {         three?: number;         four?: number;     };     two?: {         five?: number;         six?: number;     }; } 

...but Partial<UserSettings> produces this:

{     one?: {         three: number;         four: number;     };     two?: {         five: number;         six: number;     }; } 

Is it possible to use mapped types to make all the properties on all depths optional, or do I have to create an interface manually for that?

Answer 1

With the landing of Conditional Types in 2.8, we can now declare a recursive partial type as follows.

type RecursivePartial<T> = {   [P in keyof T]?:     T[P] extends (infer U)[] ? RecursivePartial<U>[] :     T[P] extends object ? RecursivePartial<T[P]> :     T[P]; }; 

Reference:

http://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-8.html

Answer 2

you could make your own mapping type, like this:

type RecursivePartial<T> = {     [P in keyof T]?: RecursivePartial<T[P]>; }; 

Unfortunately, this does not work for array-typed fields. There does not seem to be a way to do conditional type mapping yet either; i.e. limit to primitives. See https://github.com/Microsoft/TypeScript/pull/12114#issuecomment-259776847 Its possible now, see other answer.