Prevent removal of machines with assigned services

Ensures machines cannot be removed if user services are still assigned,
preventing orphaned user service records from counting against the
limit and improving data consistency.

Author: aschumann-virtualcable

src/uds/core/services/generics/fixed/service.py

@@ -28,6 +28,7 @@
 """
 Author: Adolfo Gómez, dkmaster at dkmon dot com
 """
+
 import random  # Not for cryptographic purposes, just to randomize the assignation of machines
 import abc
 import contextlib
@@ -147,9 +148,16 @@ def initialize(self, values: 'types.core.ValuesType') -> None:
             if not self.machines.value:
                 raise exceptions.ui.ValidationError(gettext('We need at least a machine'))
 
-            # Remove machines not in values from "assigned" set
+            # Do not allow removing machines that still have assigned user services.
+            # (their UserService rows would linger, counting against userservices_limit)
             with self._assigned_access() as assigned_vms:
-                assigned_vms &= set(self.machines.as_list())
+                removed_assigned = assigned_vms - set(self.machines.as_list())
+                if removed_assigned:
+                    raise exceptions.ui.ValidationError(
+                        gettext('Cannot remove machines with assigned services: {}').format(
+                            ', '.join(self.get_name(m) or m for m in sorted(removed_assigned))
+                        )
+                    )
             self.token.value = self.token.value.strip()
 
     @contextlib.contextmanager