#639: Deep clone itemmetas persistent container on clone

After this commit, spigot now creates a deep copy of the
itemmeta's persistent data container when the itemmeta
instance is cloned.

This change fixes the bug that, after cloning itemmeta, the container
instance the cloned meta would point to was equal to the original one.
This resulted in two itemmeta instances sharing a single persistent
container.

src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaItem.java

@@ -279,7 +279,7 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable, BlockDataMeta {
 
     private NBTTagCompound internalTag;
     private final Map<String, NBTBase> unhandledTags = new HashMap<String, NBTBase>();
-    private final CraftPersistentDataContainer persistentDataContainer = new CraftPersistentDataContainer(DATA_TYPE_REGISTRY);
+    private CraftPersistentDataContainer persistentDataContainer = new CraftPersistentDataContainer(DATA_TYPE_REGISTRY);
 
     private int version = CraftMagicNumbers.INSTANCE.getDataVersion(); // Internal use only
 
@@ -1197,6 +1197,7 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable, BlockDataMeta {
             if (this.hasAttributeModifiers()) {
                 clone.attributeModifiers = LinkedHashMultimap.create(this.attributeModifiers);
             }
+            clone.persistentDataContainer = new CraftPersistentDataContainer(this.persistentDataContainer.getRaw(), DATA_TYPE_REGISTRY);
             clone.hideFlag = this.hideFlag;
             clone.unbreakable = this.unbreakable;
             clone.damage = this.damage;

src/test/java/org/bukkit/craftbukkit/inventory/PersistentDataContainerTest.java

@@ -310,4 +310,20 @@ public class PersistentDataContainerTest extends AbstractTestingBase {
             return primitive;
         }
     }
+
+    @Test
+    public void testItemMetaClone() {
+        ItemMeta itemMeta = createNewItemMeta();
+        PersistentDataContainer container = itemMeta.getPersistentDataContainer();
+        itemMeta.getPersistentDataContainer().set(VALID_KEY, PersistentDataType.STRING, "notch");
+
+        ItemMeta clonedMeta = itemMeta.clone();
+        PersistentDataContainer clonedContainer = clonedMeta.getPersistentDataContainer();
+
+        assertNotSame(container, clonedContainer);
+        assertEquals(container, clonedContainer);
+
+        clonedContainer.set(VALID_KEY, PersistentDataType.STRING, "dinnerbone");
+        assertNotEquals(container, clonedContainer);
+    }
 }