Object.Partial deep and array object values

[Oikio]

🐞 Bug Report

Describe the bug

Object.Partial with deep flag changes the value of a key if it is an array by mapping array of type Type[] to (Type | undefined)[] | undefined, so it changes type type of an array.
Is it intentional or a bug? And if it is intentional, then how to avoid mapping values of the array.

Reproduce the bug

import type { Object } from 'ts-toolbelt'

const test: Object.Partial<{ foo: string[] }, 'deep'> = {} as any
test.foo // here

Expected behavior

foo?: (string | undefined)[] | undefined should be foo?: string[] | undefined

Possible Solution

Not sure if it was intentional

Screenshots

Additional context

[Oikio]

Solution to exclude array which works in our case, might be useful for someone:

type ObjectFieldsOptional<T> = {
  [P in keyof T]?: T[P] extends Array<any>
    ? T[P]
    : T[P] extends object
    ? ObjectFieldsOptional<T[P]>
    : T[P]
}