Don't allow items to swap infinitly

Fill.py

@@ -2,6 +2,8 @@ import logging
 import typing
 import collections
 import itertools
+from collections import Counter
+
 
 from BaseClasses import CollectionState, Location, MultiWorld, Item
 from worlds.generic import PlandoItem
@@ -25,6 +27,7 @@ def fill_restrictive(world: MultiWorld, base_state: CollectionState, locations,
     unplaced_items = []
     placements = []
 
+    swapped_items: Counter[Item] = Counter()
     reachable_items = {}
     for item in itempool:
         reachable_items.setdefault(item.player, []).append(item)
@@ -59,6 +62,8 @@ def fill_restrictive(world: MultiWorld, base_state: CollectionState, locations,
                 # try swaping this item with previously placed items
                 for(i, location) in enumerate(placements):
                     placed_item = location.item
+                    if swapped_items[placed_item.name] > 0:
+                        continue
                     location.item = None
                     placed_item.location = None
                     swap_state = sweep_from_pool(base_state, itempool)
@@ -67,7 +72,9 @@ def fill_restrictive(world: MultiWorld, base_state: CollectionState, locations,
                         # Add this item to the exisiting placement, and
                         # add the old item to the back of the queue
                         spot_to_fill = placements.pop(i)
-                        reachable_items.setdefault(placed_item.player, []).append(placed_item)
+                        swapped_items[placed_item.name] += 1
+                        reachable_items.setdefault(
+                            placed_item.player, []).append(placed_item)
                         itempool.append(placed_item)
                         break
                     else:

test/base/TestFill.py

@@ -150,3 +150,22 @@ class TestBase(unittest.TestCase):
         set_rule(loc0, lambda state: state.has(item2.name, player1_id))
         with pytest.raises(FillError):
             fill_restrictive(multi_world, multi_world.state, locations, items)
+
+    def test_competing_fill_restrictive(self):
+        multi_world = generate_multi_world()
+        player1_id = 1
+        player1_menu = multi_world.get_region("Menu", player1_id)
+
+        locations = generate_locations(2, player1_id, None, player1_menu)
+        items = generate_items(2, player1_id, True)
+
+        item0 = items[0]
+        item1 = items[1]
+        loc1 = locations[1]
+
+        multi_world.completion_condition[player1_id] = lambda state: state.has(
+            item0.name, player1_id) and state.has(item0.name, player1_id) and state.has(item1.name, player1_id)
+        set_rule(loc1, lambda state: state.has(item0.name, player1_id)
+                 and state.has(item1.name, player1_id))
+        with pytest.raises(FillError):
+            fill_restrictive(multi_world, multi_world.state, locations, items)