GER: Only consider usable exits when calculating dead-ends (#4701)

* Only consider usable exits when calculating whether or not a region is a dead-end

* Update EntranceLookup unit tests

* Add new dead-end test

* Add additional explanation to the new test

* minor formatting tweak

based on review feedback

---------

Co-authored-by: CodeGorilla <3672561+Ars-Ignis@users.noreply.github.com>

entrance_rando.py

@@ -50,13 +50,15 @@ class EntranceLookup:
     _random: random.Random
     _expands_graph_cache: dict[Entrance, bool]
     _coupled: bool
+    _usable_exits: set[Entrance]
 
-    def __init__(self, rng: random.Random, coupled: bool):
+    def __init__(self, rng: random.Random, coupled: bool, usable_exits: set[Entrance]):
         self.dead_ends = EntranceLookup.GroupLookup()
         self.others = EntranceLookup.GroupLookup()
         self._random = rng
         self._expands_graph_cache = {}
         self._coupled = coupled
+        self._usable_exits = usable_exits
 
     def _can_expand_graph(self, entrance: Entrance) -> bool:
         """
@@ -95,7 +97,8 @@ class EntranceLookup:
                 # randomizable exits which are not reverse of the incoming entrance.
                 # uncoupled mode is an exception because in this case going back in the door you just came in could
                 # actually lead somewhere new
-                if not exit_.connected_region and (not self._coupled or exit_.name != entrance.name):
+                if (not exit_.connected_region and (not self._coupled or exit_.name != entrance.name)
+                        and exit_ in self._usable_exits):
                     self._expands_graph_cache[entrance] = True
                     return True
                 elif exit_.connected_region and exit_.connected_region not in visited:
@@ -333,7 +336,6 @@ def randomize_entrances(
 
     start_time = time.perf_counter()
     er_state = ERPlacementState(world, coupled)
-    entrance_lookup = EntranceLookup(world.random, coupled)
     # similar to fill, skip validity checks on entrances if the game is beatable on minimal accessibility
     perform_validity_check = True
 
@@ -349,6 +351,7 @@ def randomize_entrances(
 
     # used when membership checks are needed on the exit list, e.g. speculative sweep
     exits_set = set(exits)
+    entrance_lookup = EntranceLookup(world.random, coupled, exits_set)
     for entrance in er_targets:
         entrance_lookup.add(entrance)
 

test/general/test_entrance_rando.py

@@ -65,8 +65,10 @@ class TestEntranceLookup(unittest.TestCase):
         """tests that get_targets shuffles targets between groups when requested"""
         multiworld = generate_test_multiworld()
         generate_disconnected_region_grid(multiworld, 5)
+        exits_set = set([ex for region in multiworld.get_regions(1)
+                        for ex in region.exits if not ex.connected_region])
 
-        lookup = EntranceLookup(multiworld.worlds[1].random, coupled=True)
+        lookup = EntranceLookup(multiworld.worlds[1].random, coupled=True, usable_exits=exits_set)
         er_targets = [entrance for region in multiworld.get_regions(1)
                       for entrance in region.entrances if not entrance.parent_region]
         for entrance in er_targets:
@@ -86,8 +88,10 @@ class TestEntranceLookup(unittest.TestCase):
         """tests that get_targets does not shuffle targets between groups when requested"""
         multiworld = generate_test_multiworld()
         generate_disconnected_region_grid(multiworld, 5)
+        exits_set = set([ex for region in multiworld.get_regions(1)
+                        for ex in region.exits if not ex.connected_region])
 
-        lookup = EntranceLookup(multiworld.worlds[1].random, coupled=True)
+        lookup = EntranceLookup(multiworld.worlds[1].random, coupled=True, usable_exits=exits_set)
         er_targets = [entrance for region in multiworld.get_regions(1)
                       for entrance in region.entrances if not entrance.parent_region]
         for entrance in er_targets:
@@ -99,6 +103,30 @@ class TestEntranceLookup(unittest.TestCase):
         group_order = [prev := group.randomization_group for group in retrieved_targets if prev != group.randomization_group]
         self.assertEqual([ERTestGroups.TOP, ERTestGroups.BOTTOM], group_order)
 
+    def test_selective_dead_ends(self):
+        """test that entrances that EntranceLookup has not been told to consider are ignored when finding dead-ends"""
+        multiworld = generate_test_multiworld()
+        generate_disconnected_region_grid(multiworld, 5)
+        exits_set = set([ex for region in multiworld.get_regions(1)
+                        for ex in region.exits if not ex.connected_region
+                         and ex.name != "region20_right" and ex.name != "region21_left"])
+
+        lookup = EntranceLookup(multiworld.worlds[1].random, coupled=True, usable_exits=exits_set)
+        er_targets = [entrance for region in multiworld.get_regions(1)
+                      for entrance in region.entrances if not entrance.parent_region and
+                      entrance.name != "region20_right" and entrance.name != "region21_left"]
+        for entrance in er_targets:
+            lookup.add(entrance)
+        # region 20 is the bottom left corner of the grid, and therefore only has a right entrance from region 21
+        # and a top entrance from region 15; since we've told lookup to ignore the right entrance from region 21,
+        # the top entrance from region 15 should be considered a dead-end
+        dead_end_region = multiworld.get_region("region20", 1)
+        for dead_end in dead_end_region.entrances:
+            if dead_end.name == "region20_top":
+                break
+        # there should be only this one dead-end
+        self.assertTrue(dead_end in lookup.dead_ends)
+        self.assertEqual(len(lookup.dead_ends), 1)
 
 class TestBakeTargetGroupLookup(unittest.TestCase):
     def test_lookup_generation(self):