Clone item stacks in ItemUpdateEvent constructor

Author: NichtStudioCode

invui/src/main/java/xyz/xenondevs/invui/inventory/Inventory.java

@@ -472,7 +472,9 @@ public void callClickEvent(int slot, InventoryClickEvent event) {
      * @param updateReason      The {@link UpdateReason}.
      * @param slot              The slot of the affected {@link ItemStack}.
      * @param previousItemStack The {@link ItemStack} that was previously on that slot.
+     *                          Will be cloned to prevent modifications.
      * @param newItemStack      The {@link ItemStack} that will be on that slot.
+     *                          Will be cloned to prevent modifications.
      * @return The {@link ItemPreUpdateEvent} after it has been handled by the pre update handlers.
      */
     public ItemPreUpdateEvent callPreUpdateEvent(@Nullable UpdateReason updateReason, int slot, @Nullable ItemStack previousItemStack, @Nullable ItemStack newItemStack) {
@@ -496,7 +498,9 @@ public ItemPreUpdateEvent callPreUpdateEvent(@Nullable UpdateReason updateReason
      * @param updateReason      The {@link UpdateReason}.
      * @param slot              The slot of the affected {@link ItemStack}.
      * @param previousItemStack The {@link ItemStack} that was on that slot previously.
+     *                          Will be cloned to prevent modifications.
      * @param newItemStack      The {@link ItemStack} that is on that slot now.
+     *                          Will be cloned to prevent modifications.
      */
     public void callPostUpdateEvent(@Nullable UpdateReason updateReason, int slot, @Nullable ItemStack previousItemStack, @Nullable ItemStack newItemStack) {
         if (updateReason == UpdateReason.SUPPRESSED)

invui/src/main/java/xyz/xenondevs/invui/inventory/event/ItemPreUpdateEvent.java

@@ -4,6 +4,7 @@
 import org.bukkit.inventory.ItemStack;
 import org.jspecify.annotations.Nullable;
 import xyz.xenondevs.invui.inventory.Inventory;
+import xyz.xenondevs.invui.util.ItemUtils;
 
 /**
  * An event that is called whenever a slot inside a {@link Inventory} gets updated.
@@ -38,7 +39,7 @@ public ItemPreUpdateEvent(Inventory inventory, int slot, @Nullable UpdateReason
      *                if the {@link ItemPreUpdateEvent} is not cancelled.
      */
     public void setNewItem(@Nullable ItemStack newItem) {
-        this.newItemStack = newItem;
+        this.newItemStack = ItemUtils.takeUnlessEmpty(newItem);
     }
 
     /**

invui/src/main/java/xyz/xenondevs/invui/inventory/event/ItemUpdateEvent.java

@@ -4,6 +4,7 @@
 import org.bukkit.inventory.ItemStack;
 import org.jspecify.annotations.Nullable;
 import xyz.xenondevs.invui.inventory.Inventory;
+import xyz.xenondevs.invui.util.ItemUtils;
 
 abstract class ItemUpdateEvent {
 
@@ -31,8 +32,8 @@ public ItemUpdateEvent(Inventory inventory, int slot, @Nullable UpdateReason upd
         this.inventory = inventory;
         this.slot = slot;
         this.updateReason = updateReason;
-        this.previousItemStack = previousItem;
-        this.newItemStack = newItem;
+        this.previousItemStack = ItemUtils.cloneUnlessEmpty(previousItem);
+        this.newItemStack = ItemUtils.cloneUnlessEmpty(newItem);
     }
 
     /**
@@ -63,7 +64,7 @@ public Inventory getInventory() {
     }
 
     /**
-     * Gets clone of the new {@link ItemStack} that will be there if the event isn't cancelled.
+     * Gets a clone of the new {@link ItemStack} that will be there if the event isn't cancelled.
      *
      * @return The new {@link ItemStack}
      */

invui/src/main/java/xyz/xenondevs/invui/util/ItemUtils.java

@@ -55,4 +55,17 @@ public static boolean isEmpty(@Nullable ItemStack itemStack) {
         return clone;
     }
 
+    /**
+     * Clones the given {@link ItemStack} and returns it, unless it is empty, in which case null is returned.
+     *
+     * @param itemStack The {@link ItemStack} to clone.
+     * @return The cloned {@link ItemStack} or null if it is empty.
+     */
+    public static @Nullable ItemStack cloneUnlessEmpty(@Nullable ItemStack itemStack) {
+        if (isEmpty(itemStack))
+            return null;
+        
+        return itemStack.clone();
+    }
+    
 }