#1299: Add new PersistentDataContainer methods and clean up docs

src/main/java/org/bukkit/craftbukkit/persistence/CraftPersistentDataContainer.java

@@ -54,6 +54,11 @@ public class CraftPersistentDataContainer implements PersistentDataContainer {
         return registry.isInstanceOf(type.getPrimitiveType(), value);
     }
 
+    @Override
+    public boolean has(NamespacedKey key) {
+        return this.customDataTags.get(key.toString()) != null;
+    }
+
     @Override
     public <T, Z> Z get(NamespacedKey key, PersistentDataType<T, Z> type) {
         Preconditions.checkArgument(key != null, "The NamespacedKey key cannot be null");
@@ -99,6 +104,18 @@ public class CraftPersistentDataContainer implements PersistentDataContainer {
         return this.customDataTags.isEmpty();
     }
 
+    @Override
+    public void copyTo(PersistentDataContainer other, boolean replace) {
+        Preconditions.checkArgument(other != null, "The target container cannot be null");
+
+        CraftPersistentDataContainer target = (CraftPersistentDataContainer) other;
+        if (replace) {
+            target.customDataTags.putAll(customDataTags);
+        } else {
+            customDataTags.forEach(target.customDataTags::putIfAbsent);
+        }
+    }
+
     @Override
     public PersistentDataAdapterContext getAdapterContext() {
         return this.adapterContext;

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

@@ -50,6 +50,13 @@ public class PersistentDataContainerTest extends AbstractTestingBase {
         assertThrows(IllegalArgumentException.class, () -> itemMeta.getPersistentDataContainer().has(VALID_KEY, new PrimitiveTagType<>(boolean.class)));
     }
 
+    @Test
+    public void testHasNoType() {
+        ItemMeta itemMeta = createNewItemMeta();
+        itemMeta.getPersistentDataContainer().set(VALID_KEY, PersistentDataType.INTEGER, 1); // We gotta set this so we at least try to compare it
+        assertTrue(itemMeta.getPersistentDataContainer().has(VALID_KEY));
+    }
+
     /*
         Getting a tag
      */
@@ -88,6 +95,28 @@ public class PersistentDataContainerTest extends AbstractTestingBase {
         return new NamespacedKey("test-plugin", keyName.toLowerCase());
     }
 
+    @Test
+    public void testCopyTo() {
+        PersistentDataContainer container = createComplexItemMeta().getPersistentDataContainer();
+        PersistentDataContainer target = container.getAdapterContext().newPersistentDataContainer();
+        target.set(VALID_KEY, PersistentDataType.INTEGER, 1);
+        container.set(VALID_KEY, PersistentDataType.INTEGER, 2);
+        container.copyTo(target, false);
+
+        assertEquals(1, target.get(VALID_KEY, PersistentDataType.INTEGER)); // Should not be replaced
+    }
+
+    @Test
+    public void testCopyToReplace() {
+        PersistentDataContainer container = createComplexItemMeta().getPersistentDataContainer();
+        PersistentDataContainer target = container.getAdapterContext().newPersistentDataContainer();
+        target.set(VALID_KEY, PersistentDataType.INTEGER, 1);
+        container.set(VALID_KEY, PersistentDataType.INTEGER, 2);
+        container.copyTo(target, true);
+
+        assertEquals(container, target);
+    }
+
     /*
         Removing a tag
      */