Fix phantom entity counts left by portaled mobs

src/main/java/world/bentobox/limits/listeners/EntityLimitListener.java

@@ -59,8 +59,6 @@ public class EntityLimitListener implements Listener {
     private final Limits addon;
     /** Entity UUIDs that have just spawned to prevent double-processing. */
     private final List<UUID> justSpawned = new ArrayList<>();
-    /** Entity UUIDs that are currently portaling to prevent double-decrement on cross-world removal. */
-    private final List<UUID> justPortaled = new ArrayList<>();
     /** Maps entity UUID to island ID so decrement works even when the entity dies off-island. */
     private final Map<UUID, String> entityIslandMap = new HashMap<>();
     /** Cardinal directions used for block structure detection. */
@@ -344,9 +342,6 @@ public void onEntityRemove(EntityRemoveEvent e) {
         World w = entity.getWorld();
         if (!addon.inGameModeWorld(w)) return;
 
-        // Entity is being portaled — count transfer was already handled by onEntityPortal.
-        if (justPortaled.remove(entity.getUniqueId())) return;
-
         String islandId = entityIslandMap.remove(entity.getUniqueId());
         if (islandId != null) {
             addon.getBlockLimitListener().decrementEntity(islandId, envOf(w), entity.getType());
@@ -374,8 +369,9 @@ public void onEntityPortal(EntityPortalEvent e) {
         if (fromEnv == toEnv) return;
         if (!addon.inGameModeWorld(fromWorld) && !addon.inGameModeWorld(toWorld)) return;
 
-        // Prevent onEntityRemove from double-decrementing for the source-world removal.
-        justPortaled.add(entity.getUniqueId());
+        // No EntityRemoveEvent guard is needed here: Paper suppresses the event for
+        // dimension changes (RemovalReason.CHANGED_DIMENSION carries a null Bukkit cause),
+        // so the source-world removal never reaches onEntityRemove.
 
         // Decrement at source if on a tracked island
         if (addon.inGameModeWorld(fromWorld)) {

src/test/java/world/bentobox/limits/listeners/EntityLimitListenerTest.java

@@ -37,6 +37,7 @@
 import org.bukkit.event.entity.CreatureSpawnEvent;
 import org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason;
 import org.bukkit.event.entity.EntityBreedEvent;
+import org.bukkit.event.entity.EntityPortalEvent;
 import org.bukkit.event.entity.EntityRemoveEvent;
 import org.bukkit.event.Event;
 import org.bukkit.event.block.Action;
@@ -803,6 +804,74 @@
         assertFalse(entityIslandMap().containsKey(enderman.getUniqueId()));
     }
 
+    // --- EntityPortalEvent / phantom-count tests ---
+
+    @Test
+    void testEntityPortalTransfersCountBetweenEnvironments() throws Exception {
+        Location netherLoc = mockNetherLocation();
+        LivingEntity chicken = mockEntity(EntityType.CHICKEN, location);
+        ibc.incrementEntity(Environment.NORMAL, EntityType.CHICKEN);
+
+        ell.onEntityPortal(new EntityPortalEvent(chicken, location, netherLoc));
+
+        assertEquals(0, ibc.getEntityCount(Environment.NORMAL, EntityType.CHICKEN));
+        assertEquals(1, ibc.getEntityCount(Environment.NETHER, EntityType.CHICKEN));
+        assertEquals("test-island-id", entityIslandMap().get(chicken.getUniqueId()));
+    }
+
+    @Test
+    void testPortaledEntityDeathStillDecrements() throws Exception {
+        // Regression: Paper never fires an EntityRemoveEvent for the dimension change itself
+        // (RemovalReason.CHANGED_DIMENSION has a null Bukkit cause), so the old justPortaled
+        // guard was never consumed and instead swallowed the entity's real death decrement,
+        // leaving a phantom count in the destination environment.
+        Location netherLoc = mockNetherLocation();
+        World nether = netherLoc.getWorld();
+        LivingEntity chicken = mockEntity(EntityType.CHICKEN, location);
+        ibc.incrementEntity(Environment.NORMAL, EntityType.CHICKEN);
+        ell.onEntityPortal(new EntityPortalEvent(chicken, location, netherLoc));
+        assertEquals(1, ibc.getEntityCount(Environment.NETHER, EntityType.CHICKEN));
+
+        // The entity now lives in the nether and dies there.
+        when(chicken.getWorld()).thenReturn(nether);
+        when(chicken.getLocation()).thenReturn(netherLoc);
+        ell.onEntityRemove(new EntityRemoveEvent(chicken, EntityRemoveEvent.Cause.DEATH));
+
+        assertEquals(0, ibc.getEntityCount(Environment.NETHER, EntityType.CHICKEN));
+        assertFalse(entityIslandMap().containsKey(chicken.getUniqueId()));
+    }
+
+    @Test
+    void testRoundTripPortalThenDeathLeavesNoPhantomCount() throws Exception {
+        // The reported symptom: a mob portals to the nether, comes back, and dies in the
+        // overworld — the overworld count must return to zero, not stick at a phantom 1.
+        Location netherLoc = mockNetherLocation();
+        World nether = netherLoc.getWorld();
+        LivingEntity chicken = mockEntity(EntityType.CHICKEN, location);
+        ibc.incrementEntity(Environment.NORMAL, EntityType.CHICKEN);
+
+        ell.onEntityPortal(new EntityPortalEvent(chicken, location, netherLoc));
+        when(chicken.getWorld()).thenReturn(nether);
+        when(chicken.getLocation()).thenReturn(netherLoc);
+        ell.onEntityPortal(new EntityPortalEvent(chicken, netherLoc, location));
+        when(chicken.getWorld()).thenReturn(world);
+        when(chicken.getLocation()).thenReturn(location);
+
+        ell.onEntityRemove(new EntityRemoveEvent(chicken, EntityRemoveEvent.Cause.DEATH));
+
+        assertEquals(0, ibc.getEntityCount(Environment.NORMAL, EntityType.CHICKEN));
+        assertEquals(0, ibc.getEntityCount(Environment.NETHER, EntityType.CHICKEN));
+    }
+
+    private Location mockNetherLocation() {
+        World nether = mock(World.class);
+        when(nether.getEnvironment()).thenReturn(Environment.NETHER);
+        when(addon.inGameModeWorld(nether)).thenReturn(true);
+        Location netherLoc = mock(Location.class);
+        when(netherLoc.getWorld()).thenReturn(nether);
+        return netherLoc;
+    }
+
     @SuppressWarnings("unchecked")
     private Map<UUID, String> entityIslandMap() throws Exception {
         Field f = EntityLimitListener.class.getDeclaredField("entityIslandMap");