Fix server replaying the close window packet

src/main/java/net/minestom/server/entity/Player.java

@@ -1758,6 +1758,39 @@ public class Player extends LivingEntity implements CommandSender, Localizable,
         }
     }
 
+    /**
+     * Updates the player's inventory state, given a window id to compare against.
+     * Note: This should only be used when receiving a {@link net.minestom.server.network.packet.client.play.ClientCloseWindowPacket}.
+     * Use {@link #closeInventory()} instead for more general use.
+     * @param windowId The window id to compare against.
+     */
+    public void updateCloseInventoryState(byte windowId) {
+        if (windowId == 0) {
+            // Put cursor item back in inventory if possible
+            ItemStack stack = getInventory().getCursorItem();
+            boolean success = getInventory().addItemStack(stack);
+            // Drop if inventory is full
+            if (!success) {
+                dropItem(stack);
+            }
+            getInventory().setCursorItem(ItemStack.AIR);
+        } else {
+            if (getOpenInventory() != null && windowId == getOpenInventory().getWindowId()) {
+                ItemStack stack = getOpenInventory().getCursorItem(this);
+                // Try to put item into our inventory
+                boolean success = getInventory().addItemStack(stack);
+                // Drop if inventory is full
+                if (!success) {
+                    dropItem(stack);
+                }
+                getOpenInventory().setCursorItem(this, ItemStack.AIR);
+            } else {
+                // Something has gone wrong
+                logger.warn("Tried to update inventory state with invalid window id!");
+            }
+        }
+    }
+
     /**
      * Used internally to prevent an inventory click to be processed
      * when the inventory listeners closed the inventory.

src/main/java/net/minestom/server/listener/WindowListener.java

@@ -27,8 +27,6 @@ public class WindowListener {
         final byte button = packet.button();
         final ClientClickWindowPacket.ClickType clickType = packet.clickType();
 
-        //System.out.println("Window id: " + windowId + " | slot: " + slot + " | button: " + button + " | clickType: " + clickType);
-
         boolean successful = false;
 
         // prevent click in a non-interactive slot (why does it exist?)
@@ -90,7 +88,7 @@ public class WindowListener {
         InventoryCloseEvent inventoryCloseEvent = new InventoryCloseEvent(player.getOpenInventory(), player);
         EventDispatcher.call(inventoryCloseEvent);
 
-        player.closeInventory();
+        player.updateCloseInventoryState(packet.windowId());
 
         Inventory newInventory = inventoryCloseEvent.getNewInventory();
         if (newInventory != null)
@@ -103,10 +101,10 @@ public class WindowListener {
      */
     private static void refreshCursorItem(Player player, AbstractInventory inventory) {
         ItemStack cursorItem;
-        if (inventory instanceof PlayerInventory) {
+        if (inventory instanceof PlayerInventory playerInventory) {
-            cursorItem = ((PlayerInventory) inventory).getCursorItem();
+            cursorItem = playerInventory.getCursorItem();
-        } else if (inventory instanceof Inventory) {
+        } else if (inventory instanceof Inventory standardInventory) {
-            cursorItem = ((Inventory) inventory).getCursorItem(player);
+            cursorItem = standardInventory.getCursorItem(player);
         } else {
             throw new RuntimeException("Invalid inventory: " + inventory.getClass());
         }
@@ -115,10 +113,10 @@ public class WindowListener {
     }
 
     private static void setCursor(Player player, AbstractInventory inventory, ItemStack itemStack) {
-        if (inventory instanceof PlayerInventory) {
+        if (inventory instanceof PlayerInventory playerInventory) {
-            ((PlayerInventory) inventory).setCursorItem(itemStack);
+            playerInventory.setCursorItem(itemStack);
-        } else if (inventory instanceof Inventory) {
+        } else if (inventory instanceof Inventory standardInventory) {
-            ((Inventory) inventory).setCursorItem(player, itemStack);
+            standardInventory.setCursorItem(player, itemStack);
         } else {
             throw new RuntimeException("Invalid inventory: " + inventory.getClass());
         }

src/test/java/net/minestom/server/inventory/InventoryCloseStateTest.java

@@ -0,0 +1,36 @@
+package net.minestom.server.inventory;
+
+import net.kyori.adventure.text.Component;
+import net.minestom.server.coordinate.Pos;
+import net.minestom.server.network.ConnectionState;
+import net.minestom.server.network.packet.client.play.ClientCloseWindowPacket;
+import net.minestom.server.network.packet.server.play.CloseWindowPacket;
+import net.minestom.testing.Env;
+import net.minestom.testing.EnvTest;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+@EnvTest
+public class InventoryCloseStateTest {
+
+
+    @Test
+    public void doNotReceiveClosePacketFromServerWhenSendingClientCloseWindowPacket(Env env) {
+        var instance = env.createFlatInstance();
+        var connection = env.createConnection();
+        var player = connection.connect(instance, new Pos(0, 42, 0)).join();
+        assertEquals(instance, player.getInstance());
+
+        var packetTracker = connection.trackIncoming(CloseWindowPacket.class);
+        var inventory = new Inventory(InventoryType.CHEST_2_ROW, Component.text("Test"));
+        player.openInventory(inventory);
+        player.closeInventory(); // Closes the inventory server-side, should send a CloseWindowPacket
+        player.openInventory(inventory);
+        // Send the close window packet
+        player.addPacketToQueue(ConnectionState.PLAY, new ClientCloseWindowPacket(inventory.getWindowId()));
+        player.interpretPacketQueue();
+        packetTracker.assertSingle(closeWindowPacket -> assertEquals(inventory.getWindowId(), closeWindowPacket.windowId()));
+        packetTracker.assertCount(1); // Assert we only get 1 close window packet from the closeInventory(); call
+    }
+}