Firestore security rules based on map values

Question

I want to store if a user is permitted to read a document in the document itself, based on the user\'s email address. Multiple users should have access to the same document.

Answer 1

Whenever you have (optional) nested properties you should make sure the property exists before continuing to check its' value eg.

allow read: if role in request.auth.token && request.auth.token[role] == true

in your case:

allow read: if test in resource.data.shared && resource.data.shared.test == true

, I was struggling a long time with roles until I realized that on non-admin users the admin field is undefined and firestore rules just crashes and doesn't continue checking other possible matches.

For a user without token.admin, this will always crash no matter if you have other matches that are true eg:

function userHasRole(role) {
  return isSignedIn() && request.auth.token[role] == true
}