deep-required

DeepRequired<Type> constructs a type by picking all properties from type Type recursively and setting as required

interface DeepPartialCompany {
  name?: string | undefined;
  employees?: ({ name?: string | undefined } | undefined)[] | undefined;
}

type Company = DeepRequired<DeepPartialCompany>;
//   ^? { name: string; employees: { name: string }[] }

Useful when deep partial object type is a source of truth and you need to have required object type, e.g. for default values:

const defaultCompany: Company = {
  name: "Unidentified company name",
  employees: [
    {
      name: "Unidentified CEO name",
    },
  ],
};

TS Playground – https://tsplay.dev/Nr8KaW

It's different from DeepNonNullable as it doesn't remove null:

interface Person {
  name?: string | null | undefined;
}

type NonNullablePerson = DeepNonNullable<Person>;
//   ^? { name?: string | undefined; }
type RequiredPerson = DeepRequired<Person>;
//   ^? { name: string | null; }

TS Playground – https://tsplay.dev/N9jy8m