I have this TypeScript React code, for fetching a firestore collection (using react-firebase-hooks):

const [membersSnapshot, loading, error] = useCollectionData(
  query(
    collection(db, USERS_COLLECTION).withConverter(UserConverter.prototype),
    where(UserFields.FamilyId, "==", familyId)
  )
);

console.assert(error === undefined, error);

Which without rules, works as expected (assertion not failing).

I have added this rule (I’m adding only the relevant parts):

function getUser() {
  return getUserData(request.auth.uid);
}
    
function getUserData(userId) {
  return get(/databases/$(database)/documents/users/$(userId)).data;
}

function isSignedIn() {
  return request.auth != null;
} 

function inSameFamily(userId) {
  return getUser().familyId == getUserData(userId).familyId;
}

match /users/{userId} {
  allow read: if isSignedIn() && request.auth.uid == userId || isSignedIn() && inSameFamily(userId); 
}

With this rule, the assertion fails,

Assertion failed: FirebaseError: Missing or insufficient permissions.

and I do not understand what’s the problem.

I tried to change the where condition, to:

where(UserFields.Email, "==", userEmail)

and expected it to not fail when I’m trying to get the user itself, but it failed.

Please help…