Temporary fix with inventory held click

src/main/java/net/minestom/server/benchmark/BenchmarkManager.java

@@ -8,6 +8,7 @@ import java.lang.management.ManagementFactory;
 import java.lang.management.ThreadInfo;
 import java.lang.management.ThreadMXBean;
 import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
 
 import static net.minestom.server.MinecraftServer.*;
 
@@ -27,7 +28,7 @@ public class BenchmarkManager {
     private Map<Long, Long> lastUserTimeMap = new HashMap<>();
     private Map<Long, Long> lastBlockedMap = new HashMap<>();
 
-    private Map<String, ThreadResult> resultMap = new HashMap<>();
+    private Map<String, ThreadResult> resultMap = new ConcurrentHashMap<>();
 
     private boolean enabled = false;
     private volatile boolean stop = false;

src/main/java/net/minestom/server/instance/Chunk.java

@@ -333,21 +333,22 @@ public class Chunk implements Viewable {
     }
 
     public ChunkDataPacket getFreshFullDataPacket() {
-        ChunkDataPacket fullDataPacket = new ChunkDataPacket();
+        ChunkDataPacket fullDataPacket = getFreshPacket();
         fullDataPacket.fullChunk = true;
-        fullDataPacket.biomes = biomes.clone();
-        fullDataPacket.chunkX = chunkX;
-        fullDataPacket.chunkZ = chunkZ;
-        fullDataPacket.blocksId = blocksId.clone();
-        fullDataPacket.customBlocksId = customBlocksId.clone();
-        fullDataPacket.blockEntities = new CopyOnWriteArraySet<>(blockEntities);
-        fullDataPacket.blocksData = new Int2ObjectOpenHashMap<>(blocksData);
         return fullDataPacket;
     }
 
     public ChunkDataPacket getFreshPartialDataPacket() {
-        ChunkDataPacket fullDataPacket = new ChunkDataPacket();
+        ChunkDataPacket fullDataPacket = getFreshPacket();
         fullDataPacket.fullChunk = false;
+        return fullDataPacket;
+    }
+
+    /**
+     * @return a {@link ChunkDataPacket} containing a copy this chunk data
+     */
+    private ChunkDataPacket getFreshPacket() {
+        ChunkDataPacket fullDataPacket = new ChunkDataPacket();
         fullDataPacket.biomes = biomes.clone();
         fullDataPacket.chunkX = chunkX;
         fullDataPacket.chunkZ = chunkZ;

src/main/java/net/minestom/server/inventory/Inventory.java

@@ -328,6 +328,9 @@ public class Inventory implements InventoryModifier, InventoryClickHandler, View
         if (!clickResult.isCancel())
             callClickEvent(player, this, slot, ClickType.CHANGE_HELD, clicked, getCursorItem(player));
 
+        // Weird synchronization issue when omitted
+        updateFromClick(clickResult, player);
+
         return !clickResult.isCancel();
     }
 

src/main/java/net/minestom/server/inventory/PlayerInventory.java

@@ -219,14 +219,14 @@ public class PlayerInventory implements InventoryModifier, InventoryClickHandler
 
             this.items[slot] = itemStack;
 
-            // Refresh slot
-            update();
-            //refreshSlot(slot); seems to break things concerning +64 stacks
-
             // Sync equipment
             if (equipmentSlot != null) {
                 player.syncEquipment(equipmentSlot);
             }
+
+            // Refresh slot
+            update();
+            //refreshSlot(slot); seems to break things concerning +64 stacks
         }
     }
 
@@ -365,8 +365,9 @@ public class PlayerInventory implements InventoryModifier, InventoryClickHandler
 
         InventoryClickResult clickResult = clickProcessor.changeHeld(null, player, slot, key, clicked, heldItem);
 
-        if (clickResult.doRefresh())
+        if (clickResult.doRefresh()) {
             sendSlotRefresh((short) slot, clicked);
+        }
 
         setItemStack(slot, OFFSET, clickResult.getClicked());
         setItemStack(key, clickResult.getCursor());
@@ -374,6 +375,9 @@ public class PlayerInventory implements InventoryModifier, InventoryClickHandler
         if (!clickResult.isCancel())
             callClickEvent(player, null, slot, ClickType.CHANGE_HELD, clicked, getCursorItem());
 
+        // Weird synchronization issue when omitted
+        update();
+
         return !clickResult.isCancel();
     }
 

src/main/java/net/minestom/server/inventory/click/InventoryClickProcessor.java

@@ -145,8 +145,8 @@ public class InventoryClickProcessor {
 
         if (clicked.isAir()) {
             // Set held item [key] to slot
-            resultClicked = ItemStack.getAirItem();
+            resultClicked = cursor.clone();
-            resultHeld = clicked.clone();
+            resultHeld = ItemStack.getAirItem();
         } else {
             if (cursor.isAir()) {
                 // if held item [key] is air then set clicked to held