TypeScript cast as Partial<T> but keys must exist

Question

I'm in need of two utility types: one subset of a type with matching value types and one that only needs the keys to exist in the other type.
I came up with the following which seems ok at first glance but I can't help but wonder if I'm doing something that is already built into TS (v4.7).

Update:
The problem why I was working on this was not with the type itself but with casting. Casting { nammme: 'John' as any } as Partial<Person> works, which I want to prevent. I need to override the type of some properties (but preferably not all).

// This works...
const fields: Partial<DbUser> = {
  organizationId: FieldValue.delete() as any,
  groups: FieldValue.delete() as any,
};

return getFirestore()
  .collection(constants.dbCollections.users)
  .doc(context.auth.uid)
  .update(fields);

// This allows typos...
return getFirestore()
  .collection(constants.dbCollections.users)
  .doc(context.auth.uid)
  .update({
    organizationId: FieldValue.delete() as any,
    groups: FieldValue.delete() as any,
    typoooo: 1 as any,
} as Partial<DbUser>);

Code example

type Person = {
  name: string;
  age: number;
};

export type KeysIn<T> = {
  [key in keyof Partial<T>]: any;
};

export type MustContainKeyButTypeOfKeyCanBeOverwritten<T> = unknown; // ?

// Valid: Key exists in Person
const valid1: KeysIn<Person> = {
  name: 0,
};

// Valid: Key exists in Person and type matches
const valid2: Partial<Person> = {
  name: '',
};

// Invalid: Key does not exist in Person
const invalid1: KeysIn<Person> = {
  x: true,
};

// Invalid: Key exists in Person but type does not match
const invalid2: Partial<Person> = {
  name: 0,
};

// Invalid: Key does not exist in Person
const invalid3: Partial<Person> = {
  x: true,
};

// Typo with cast to any
const invalid4: KeysIn<Person> = {
  namessss: '' as any,
};

const invalid5 = {
  namessss: '' as any,
} as Partial<Person>; // Why is this valid?

const invalid6 = {
  namessss: '' as any,
} as KeysIn<Person>; // Why is this valid? I need this to be invalid

const idealExample: MustContainKeyButTypeOfKeyCanBeOverwritten<Person> = {
  name: 1 as any, // Allowed type override
  aggggggge: 1, // Typo, invalid
  age: '2', // Wrong type, invalid
};

Can I override only certain keys with new types while preventing typos?

^stackblitz

Answer 1

Partial does what you want out of Subset .

export type Subset<T> = Partial<T>;

For KeysIn I think your definition makes sense, an alternative is the following.

export type KeysIn<T> = Partial<Record<keyof T, any>>;