Remove weird single-CP supply route edge case.

A CP with a factory would be able to supply itself, but was not in a
supply route if it was the only connected friendly CP. When the player
starts with only one base against an enemy base this meant that it was
in no supply route, causing it to not be a recruitment location or a
place to buy more than a reserve of vehicles automatically.

game/event/event.py

@@ -551,8 +551,6 @@ class UnitsDeliveryEvent:
             return self.destination
 
         supply_route = SupplyRoute.for_control_point(self.destination)
-        if supply_route is None:
-            return None
 
         sources = []
         for control_point in supply_route:

game/theater/controlpoint.py

@@ -346,11 +346,7 @@ class ControlPoint(MissionTarget, ABC):
 
         from game.theater.supplyroutes import SupplyRoute
 
-        supply_route = SupplyRoute.for_control_point(self)
-        if supply_route is None:
-            return False
-
-        for cp in supply_route:
+        for cp in SupplyRoute.for_control_point(self):
             if cp.can_recruit_ground_units(game):
                 return True
         return False

game/theater/supplyroutes.py

@@ -42,11 +42,14 @@ class SupplyRoute:
     def __iter__(self) -> Iterator[ControlPoint]:
         yield from self.control_points
 
+    def __len__(self) -> int:
+        return len(self.control_points)
+
     @classmethod
-    def for_control_point(cls, control_point: ControlPoint) -> Optional[SupplyRoute]:
+    def for_control_point(cls, control_point: ControlPoint) -> SupplyRoute:
         connected_friendly_points = control_point.transitive_connected_friendly_points()
         if not connected_friendly_points:
-            return None
+            return SupplyRoute([control_point])
         return SupplyRoute([control_point] + connected_friendly_points)
 
     def shortest_path_between(

game/transfers.py

@@ -40,8 +40,6 @@ class RoadTransferOrder(TransferOrder):
 
     def path(self) -> List[ControlPoint]:
         supply_route = SupplyRoute.for_control_point(self.position)
-        if supply_route is None:
-            raise RuntimeError(f"Supply route from {self.position.name} interrupted")
         return supply_route.shortest_path_between(self.position, self.destination)
 
 
@@ -83,7 +81,7 @@ class PendingTransfers:
             return True
 
         supply_route = SupplyRoute.for_control_point(transfer.destination)
-        if supply_route is None or transfer.position not in supply_route:
+        if transfer.position not in supply_route:
             logging.info(
                 f"Route from {transfer.position.name} to {transfer.destination.name} "
                 "was cut off."

qt_ui/windows/basemenu/QBaseMenu2.py

@@ -105,7 +105,7 @@ class QBaseMenu2(QDialog):
 
     @property
     def has_transfer_destinations(self) -> bool:
-        return SupplyRoute.for_control_point(self.cp) is not None
+        return len(SupplyRoute.for_control_point(self.cp)) > 1
 
     @property
     def can_repair_runway(self) -> bool: