SpiceDB having multiple caveats on resources of the same type may improperly result in no permission

Background

Multiple caveats over the same indirect subject type on the same relation can result in no permission being returned when permission is expected

For example, given this schema:

definition user {}

caveat somecaveat(somefield int) {
  somefield == 42
}

definition group {
  relation member: user
}

definition resource {
  relation viewer: group#member with somecaveat
  permission view = folder->view
}

If the resource has multiple groups, and each group is caveated, it is possible for the returned permission to be “no permission” when permission is expected.

Impact

Permission is returned as NO_PERMISSION when PERMISSION is expected on the CheckPermission API.

Workarounds

Do not use caveats or do not use caveats on an indirect subject type with multiple entries