Firestore security rule get() not work

Question

The solution is in the end of the post. Check it out.

Решение проблемы в конце поста. Дочитайте.

just a simple question: whats wrong with this and why this is not working?

Trying to get access with user who has role 'admin' in users section to the /titles/{anyTitle} but still get

Missing or insufficient permissions.

service cloud.firestore {
  match /databases/{database}/documents {
    match /{document=**} {
      allow write: if false;
      allow read: if false;
    }
    function userCanWrite () {
      return get(/databases/{database}/documents/users/$(request.auth.uid)).data.role == "admin";
    }
    match /titles/{anyTitle=**} {
      allow read: if request.auth != null;
      allow write: if userCanWrite();
    }
  }
}

Here is my database structure

P.S.

I tried another rule from official documents get(/databases/{database}/documents/users/$(request.auth.uid‌​)).data.isAdmin == true;

and this is not working too

UPDATE: CORRECT WAY TO DO IT

Support helped me find the solution this is how you should do:

db structure:

users -> {{ userid }} -> { role: "admin" }

database rule settings:

get(usersPath/$(request.auth.uid)).role == "admin" || get(usersPath/$(request.auth.uid)).data.role == "admin";

Answer 1

I contacted to the Firebase support to report that bug and they gave me a temporary solution on this. It seems that they are having a bug in their systems on the security rules side. They say that the documentation is ok, but for now we should workaround this way:

get(path).data.field == true || get(path).field == true;

Because the bug is that data object isn't populated, you should check both properties. There's no ETA for launching a solution on this bug, so I asked they if they could give me an advice when they solved this issue, so I'll keep this answer up-to-date with their information.