Item Mutation Fixes

paper-api/src/main/java/org/bukkit/event/block/InventoryBlockStartEvent.java

@@ -17,7 +17,7 @@ import org.jetbrains.annotations.NotNull;
 public class InventoryBlockStartEvent extends BlockEvent {
 
     private static final HandlerList handlers = new HandlerList();
-    private final ItemStack source;
+    protected ItemStack source; // Paper
 
     public InventoryBlockStartEvent(@NotNull final Block block, @NotNull ItemStack source) {
         super(block);

paper-api/src/main/java/org/bukkit/event/enchantment/EnchantItemEvent.java

@@ -20,7 +20,7 @@ import org.jetbrains.annotations.NotNull;
 public class EnchantItemEvent extends InventoryEvent implements Cancellable {
     private static final HandlerList handlers = new HandlerList();
     private final Block table;
-    private final ItemStack item;
+    private ItemStack item; // Paper
     private int level;
     private boolean cancelled;
     private final Map<Enchantment, Integer> enchants;
@@ -72,6 +72,17 @@ public class EnchantItemEvent extends InventoryEvent implements Cancellable {
         return item;
     }
 
+    // Paper start
+    /**
+     * Sets the item to be enchanted
+     *
+     * @param item item
+     */
+    public void setItem(@NotNull final ItemStack item) {
+        this.item = item;
+    }
+    // Paper end
+
     /**
      * Gets the cost (minimum level) which is displayed as a number on the right
      * hand side of the enchantment offer.