Item impl cleanup

src/main/java/net/minestom/server/item/ItemMeta.java

@@ -53,7 +53,7 @@ public class ItemMeta implements TagReadable, Writeable {
         this.canPlaceOn = Set.copyOf(metaBuilder.canPlaceOn);
 
         this.metaBuilder = metaBuilder;
-        this.nbt = metaBuilder.nbt();
+        this.nbt = metaBuilder.nbt.toCompound();
     }
 
     @Contract(value = "_, -> new", pure = true)

src/main/java/net/minestom/server/item/ItemMetaBuilder.java

@@ -15,17 +15,11 @@ import org.jglrxavpok.hephaistos.nbt.*;
 import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 
 import java.util.*;
-import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
 
 public abstract class ItemMetaBuilder implements TagWritable {
-
+    MutableNBTCompound nbt = new MutableNBTCompound();
-    private static final AtomicReferenceFieldUpdater<ItemMetaBuilder, NBTCompound> NBT_UPDATER =
-            AtomicReferenceFieldUpdater.newUpdater(ItemMetaBuilder.class, NBTCompound.class, "nbt");
-
-    protected volatile boolean built = false;
-    private volatile NBTCompound nbt = new NBTCompound();
 
     protected int damage;
     protected boolean unbreakable;
@@ -106,7 +100,7 @@ public abstract class ItemMetaBuilder implements TagWritable {
     public @NotNull ItemMetaBuilder enchantments(@NotNull Map<Enchantment, Short> enchantments) {
         this.enchantmentMap = new HashMap<>(enchantments);
         handleMap(enchantmentMap, "Enchantments", () -> {
-            MutableNBTCompound mutableCopy = new MutableNBTCompound(nbt);
+            MutableNBTCompound mutableCopy = nbt.toMutableCompound();
             NBTUtils.writeEnchant(mutableCopy, "Enchantments", enchantmentMap);
             return mutableCopy.get("Enchantments");
         });
@@ -205,24 +199,11 @@ public abstract class ItemMetaBuilder implements TagWritable {
 
     protected abstract @NotNull Supplier<@NotNull ItemMetaBuilder> getSupplier();
 
-    protected synchronized void mutateNbt(Consumer<MutableNBTCompound> consumer) {
+    protected void mutateNbt(Consumer<MutableNBTCompound> consumer) {
-        MutableNBTCompound copy = new MutableNBTCompound(nbt);
+        consumer.accept(nbt);
-        consumer.accept(copy);
-        if (built) {
-            built = false;
-            final var currentNbt = nbt;
-            NBT_UPDATER.compareAndSet(this, currentNbt, copy.toCompound());
-        } else {
-            nbt = copy.toCompound();
-        }
-    }
-
-    protected synchronized NBTCompound nbt() {
-        return nbt;
     }
 
     protected @NotNull ItemMeta generate() {
-        this.built = true;
         return build();
     }
 
@@ -280,8 +261,8 @@ public abstract class ItemMetaBuilder implements TagWritable {
     @Contract(value = "_, _ -> new", pure = true)
     public static @NotNull ItemMetaBuilder fromNBT(@NotNull ItemMetaBuilder src, @NotNull NBTCompound nbtCompound) {
         ItemMetaBuilder dest = src.getSupplier().get();
-        dest.nbt = nbtCompound;
+        dest.nbt = nbtCompound.toMutableCompound();
-        NBTUtils.loadDataIntoMeta(dest, dest.nbt);
+        NBTUtils.loadDataIntoMeta(dest, nbtCompound);
         return dest;
     }
 

src/main/java/net/minestom/server/item/ItemStackBuilder.java

@@ -112,8 +112,7 @@ public class ItemStackBuilder {
 
     @Contract(value = "-> new", pure = true)
     public @NotNull ItemStack build() {
-        if (amount < 1)
+        if (amount < 1) return ItemStack.AIR;
-            return ItemStack.AIR;
         return new ItemStack(material, amount, metaBuilder.generate(), stackingRule);
     }
 

src/main/java/net/minestom/server/item/metadata/FireworkMeta.java

@@ -14,7 +14,6 @@ import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.function.Supplier;
-import java.util.stream.Collectors;
 
 public class FireworkMeta extends ItemMeta implements ItemMetaBuilder.Provider<FireworkMeta.Builder> {
 

src/main/java/net/minestom/server/item/metadata/PotionMeta.java

@@ -16,7 +16,6 @@ import java.time.Duration;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.function.Supplier;
-import java.util.stream.Collectors;
 
 public class PotionMeta extends ItemMeta implements ItemMetaBuilder.Provider<PotionMeta.Builder> {
 

src/main/java/net/minestom/server/item/metadata/WritableBookMeta.java

@@ -13,7 +13,6 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
 import java.util.function.Supplier;
-import java.util.stream.Collectors;
 
 public class WritableBookMeta extends ItemMeta implements ItemMetaBuilder.Provider<WritableBookMeta.Builder> {
 

src/main/java/net/minestom/server/item/metadata/WrittenBookMeta.java

@@ -14,7 +14,6 @@ import org.jglrxavpok.hephaistos.nbt.*;
 
 import java.util.*;
 import java.util.function.Supplier;
-import java.util.stream.Collectors;
 
 public class WrittenBookMeta extends ItemMeta implements ItemMetaBuilder.Provider<WrittenBookMeta.Builder> {
 

src/main/java/net/minestom/server/item/rule/VanillaStackingRule.java

@@ -19,8 +19,7 @@ public final class VanillaStackingRule implements StackingRule {
 
     @Override
     public @NotNull ItemStack apply(@NotNull ItemStack item, int amount) {
-        if (amount > 0) return item.withAmount(amount);
+        return amount > 0 ? item.withAmount(amount) : ItemStack.AIR;
-        return ItemStack.AIR;
     }
 
     @Override

src/test/java/item/ItemTest.java

@@ -103,4 +103,14 @@ public class ItemTest {
         enchantments = item.getMeta().getEnchantmentMap();
         assertEquals(enchantments.get(Enchantment.EFFICIENCY), (short) 10);
     }
+
+    @Test
+    public void testBuilderReuse() {
+        var builder = ItemStack.builder(Material.DIAMOND);
+        var item1 = builder.build();
+        var item2 = builder.displayName(Component.text("Name")).build();
+        assertNull(item1.getDisplayName());
+        assertNotNull(item2.getDisplayName());
+        assertNotEquals(item1, item2, "Item builder should be reusable");
+    }
 }

src/test/java/regressions/ItemMetaBuilderRegressions.java

@@ -4,7 +4,6 @@ import net.minestom.server.item.ItemMeta;
 import net.minestom.server.item.ItemMetaBuilder;
 import org.jetbrains.annotations.NotNull;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
-import org.jglrxavpok.hephaistos.nbt.NBTShort;
 import org.jglrxavpok.hephaistos.nbt.NBTString;
 import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 import org.junit.jupiter.api.Test;