From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Noah van der Aa <ndvdaa@gmail.com>
Date: Tue, 3 Aug 2021 17:28:27 +0200
Subject: [PATCH] Hide unnecessary itemmeta from clients


diff --git a/src/main/java/net/minecraft/server/level/ServerEntity.java b/src/main/java/net/minecraft/server/level/ServerEntity.java
index 319dfa82dff1fe188a52bed5aa2d39575853b793..919758363c7b703cb200582768e68c97ce5c807a 100644
--- a/src/main/java/net/minecraft/server/level/ServerEntity.java
+++ b/src/main/java/net/minecraft/server/level/ServerEntity.java
@@ -311,7 +311,7 @@ public class ServerEntity {
                 if (!itemstack.isEmpty()) {
                     // Paper start - prevent oversized data
                     final ItemStack sanitized = LivingEntity.sanitizeItemStack(itemstack.copy(), false);
-                    list.add(Pair.of(enumitemslot, sanitized));
+                    list.add(Pair.of(enumitemslot, ((LivingEntity) this.entity).stripMeta(sanitized, false))); // Paper - remove unnecessary item meta
                     // Paper end
                 }
             }
diff --git a/src/main/java/net/minecraft/world/entity/LivingEntity.java b/src/main/java/net/minecraft/world/entity/LivingEntity.java
index d8522072adb93d47fdd7cfa947132c23c2386952..8dc54061802f0253193bda79bded1d5265591519 100644
--- a/src/main/java/net/minecraft/world/entity/LivingEntity.java
+++ b/src/main/java/net/minecraft/world/entity/LivingEntity.java
@@ -3114,7 +3114,7 @@ public abstract class LivingEntity extends Entity {
 
             // Paper start - prevent oversized data
             ItemStack toSend = sanitizeItemStack(itemstack1, true);
-            list.add(Pair.of(enumitemslot, toSend));
+            list.add(Pair.of(enumitemslot, stripMeta(toSend, toSend == itemstack1))); // Paper - hide unnecessary item meta
             // Paper end
             switch (enumitemslot.getType()) {
                 case HAND:
@@ -3128,6 +3128,59 @@ public abstract class LivingEntity extends Entity {
         ((ServerLevel) this.level).getChunkSource().broadcast(this, new ClientboundSetEquipmentPacket(this.getId(), list));
     }
 
+    // Paper start - hide unnecessary item meta
+    public ItemStack stripMeta(final ItemStack itemStack, final boolean copyItemStack) {
+        if (itemStack.isEmpty() || (!itemStack.hasTag() && itemStack.getCount() < 2)) {
+            return itemStack;
+        }
+
+        final ItemStack copy = copyItemStack ? itemStack.copy() : itemStack;
+        if (level.paperConfig().anticheat.obfuscation.items.hideDurability) {
+            // Only show damage values for elytra's, since they show a different texture when broken.
+            if (!copy.is(Items.ELYTRA) || copy.getDamageValue() < copy.getMaxDamage() - 1) {
+                copy.setDamageValue(0);
+            }
+        }
+
+        if (level.paperConfig().anticheat.obfuscation.items.hideItemmeta) {
+            // Some resource packs show different textures when there is more than one item. Since this shouldn't provide a big advantage,
+            // we'll tell the client if there's one or (more than) two items.
+            copy.setCount(copy.getCount() > 1 ? 2 : 1);
+            // We can't just strip out display, leather helmets still use the display.color tag.
+            final CompoundTag tag = copy.getTag();
+            if (tag != null) {
+                if (tag.get("display") instanceof CompoundTag displayTag) {
+                    displayTag.remove("Lore");
+                    displayTag.remove("Name");
+                }
+
+                if (tag.get("Enchantments") instanceof ListTag enchantmentsTag && !enchantmentsTag.isEmpty()) {
+                    // The client still renders items with the enchantment glow if the enchantments tag contains at least one (empty) child.
+                    ListTag enchantments = new ListTag();
+                    CompoundTag fakeEnchantment = new CompoundTag();
+                    // Soul speed boots generate client side particles.
+                    if (EnchantmentHelper.getItemEnchantmentLevel(Enchantments.SOUL_SPEED, itemStack) > 0) {
+                        fakeEnchantment.putString("id", org.bukkit.enchantments.Enchantment.SOUL_SPEED.getKey().asString());
+                        fakeEnchantment.putInt("lvl", 1);
+                    }
+                    enchantments.add(fakeEnchantment);
+                    tag.put("Enchantments", enchantments);
+                }
+                tag.remove("AttributeModifiers");
+
+                // Books
+                tag.remove("author");
+                tag.remove("filtered_title");
+                tag.remove("pages");
+                tag.remove("filtered_pages");
+                tag.remove("title");
+                tag.remove("generation");
+            }
+        }
+        return copy;
+    }
+    // Paper end
+
     // Paper start - prevent oversized data
     public static ItemStack sanitizeItemStack(final ItemStack itemStack, final boolean copyItemStack) {
         if (itemStack.isEmpty() || !itemStack.hasTag()) {