Fix item duplication and teleport issues

This notably fixes the newest "Donkey Dupe", but also fixes a lot
of dupe bugs in general around nether portals and entity world transfer

We also fix item duplication generically by anytime we clone an item
to drop it on the ground, destroy the source item.

This avoid an itemstack ever existing twice in the world state pre
clean up stage.

So even if something NEW comes up, it would be impossible to drop the
same item twice because the source was destroyed.

paper-server/patches/sources/net/minecraft/world/entity/Entity.java.patch

@@ -141,9 +141,9 @@
 +    }
 +    // Paper end - Share random for entities to make them more random
 +    public org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason spawnReason; // Paper - Entity#getEntitySpawnReason
- 
-+    private CraftEntity bukkitEntity;
 +
++    private CraftEntity bukkitEntity;
+ 
 +    public CraftEntity getBukkitEntity() {
 +        if (this.bukkitEntity == null) {
 +            this.bukkitEntity = CraftEntity.getEntity(this.level.getCraftServer(), this);
@@ -538,17 +538,15 @@
                  if (!this.level().isClientSide() || this.isControlledByLocalInstance()) {
                      Entity.MovementEmission entity_movementemission = this.getMovementEmission();
  
-@@ -1131,8 +1455,22 @@
+@@ -1133,6 +1457,20 @@
- 
-     protected SoundEvent getSwimHighSpeedSplashSound() {
          return SoundEvents.GENERIC_SPLASH;
-+    }
+     }
-+
+ 
 +    // CraftBukkit start - Add delegate methods
 +    public SoundEvent getSwimSound0() {
 +        return this.getSwimSound();
-     }
++    }
- 
++
 +    public SoundEvent getSwimSplashSound0() {
 +        return this.getSwimSplashSound();
 +    }
@@ -891,17 +889,19 @@
      protected abstract void readAdditionalSaveData(CompoundTag nbt);
  
      protected abstract void addAdditionalSaveData(CompoundTag nbt);
-@@ -2153,9 +2654,22 @@
+@@ -2153,9 +2654,23 @@
          if (stack.isEmpty()) {
              return null;
          } else {
+-            ItemEntity entityitem = new ItemEntity(world, this.getX(), this.getY() + (double) yOffset, this.getZ(), stack);
 +            // CraftBukkit start - Capture drops for death event
 +            if (this instanceof net.minecraft.world.entity.LivingEntity && !((net.minecraft.world.entity.LivingEntity) this).forceDrops) {
-+                ((net.minecraft.world.entity.LivingEntity) this).drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asBukkitCopy(stack));
++                ((net.minecraft.world.entity.LivingEntity) this).drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asCraftMirror(stack)); // Paper - mirror so we can destroy it later
 +                return null;
 +            }
 +            // CraftBukkit end
-             ItemEntity entityitem = new ItemEntity(world, this.getX(), this.getY() + (double) yOffset, this.getZ(), stack);
++            ItemEntity entityitem = new ItemEntity(world, this.getX(), this.getY() + (double) yOffset, this.getZ(), stack.copy()); // Paper - copy so we can destroy original
++            stack.setCount(0); // Paper - destroy this item - if this ever leaks due to game bugs, ensure it doesn't dupe
  
              entityitem.setDefaultPickUpDelay();
 +            // CraftBukkit start
@@ -914,7 +914,7 @@
              world.addFreshEntity(entityitem);
              return entityitem;
          }
-@@ -2184,6 +2698,12 @@
+@@ -2184,6 +2699,12 @@
          if (this.isAlive() && this instanceof Leashable leashable) {
              if (leashable.getLeashHolder() == player) {
                  if (!this.level().isClientSide()) {
@@ -927,7 +927,7 @@
                      if (player.hasInfiniteMaterials()) {
                          leashable.removeLeash();
                      } else {
-@@ -2200,6 +2720,13 @@
+@@ -2200,6 +2721,13 @@
  
              if (itemstack.is(Items.LEAD) && leashable.canHaveALeashAttachedToIt()) {
                  if (!this.level().isClientSide()) {
@@ -941,7 +941,7 @@
                      leashable.setLeashedTo(player, true);
                  }
  
-@@ -2265,7 +2792,7 @@
+@@ -2265,7 +2793,7 @@
      }
  
      public boolean showVehicleHealth() {
@@ -950,7 +950,7 @@
      }
  
      public boolean startRiding(Entity entity, boolean force) {
-@@ -2273,7 +2800,7 @@
+@@ -2273,7 +2801,7 @@
              return false;
          } else if (!entity.couldAcceptPassenger()) {
              return false;
@@ -959,7 +959,7 @@
              return false;
          } else {
              for (Entity entity1 = entity; entity1.vehicle != null; entity1 = entity1.vehicle) {
-@@ -2285,11 +2812,32 @@
+@@ -2285,11 +2813,32 @@
              if (!force && (!this.canRide(entity) || !entity.canAddPassenger(this))) {
                  return false;
              } else {
@@ -993,7 +993,7 @@
                  this.vehicle = entity;
                  this.vehicle.addPassenger(this);
                  entity.getIndirectPassengersStream().filter((entity2) -> {
-@@ -2314,19 +2862,30 @@
+@@ -2314,19 +2863,30 @@
      }
  
      public void removeVehicle() {
@@ -1026,7 +1026,7 @@
      protected void addPassenger(Entity passenger) {
          if (passenger.getVehicle() != this) {
              throw new IllegalStateException("Use x.startRiding(y), not y.addPassenger(x)");
-@@ -2349,21 +2908,53 @@
+@@ -2349,21 +2909,53 @@
          }
      }
  
@@ -1086,7 +1086,7 @@
      }
  
      protected boolean canAddPassenger(Entity passenger) {
-@@ -2464,7 +3055,7 @@
+@@ -2464,7 +3056,7 @@
                      if (teleporttransition != null) {
                          ServerLevel worldserver1 = teleporttransition.newLevel();
  
@@ -1095,7 +1095,7 @@
                              this.teleport(teleporttransition);
                          }
                      }
-@@ -2547,7 +3138,7 @@
+@@ -2547,7 +3139,7 @@
      }
  
      public boolean isCrouching() {
@@ -1104,7 +1104,7 @@
      }
  
      public boolean isSprinting() {
-@@ -2563,7 +3154,7 @@
+@@ -2563,7 +3155,7 @@
      }
  
      public boolean isVisuallySwimming() {
@@ -1113,7 +1113,7 @@
      }
  
      public boolean isVisuallyCrawling() {
-@@ -2571,6 +3162,13 @@
+@@ -2571,6 +3163,13 @@
      }
  
      public void setSwimming(boolean swimming) {
@@ -1127,7 +1127,7 @@
          this.setSharedFlag(4, swimming);
      }
  
-@@ -2609,6 +3207,7 @@
+@@ -2609,6 +3208,7 @@
  
      @Nullable
      public PlayerTeam getTeam() {
@@ -1135,7 +1135,7 @@
          return this.level().getScoreboard().getPlayersTeam(this.getScoreboardName());
      }
  
-@@ -2624,8 +3223,12 @@
+@@ -2624,8 +3224,12 @@
          return this.getTeam() != null ? this.getTeam().isAlliedTo(team) : false;
      }
  
@@ -1149,7 +1149,7 @@
      }
  
      public boolean getSharedFlag(int index) {
-@@ -2644,7 +3247,7 @@
+@@ -2644,7 +3248,7 @@
      }
  
      public int getMaxAirSupply() {
@@ -1158,7 +1158,7 @@
      }
  
      public int getAirSupply() {
-@@ -2652,7 +3255,18 @@
+@@ -2652,7 +3256,18 @@
      }
  
      public void setAirSupply(int air) {
@@ -1178,7 +1178,7 @@
      }
  
      public int getTicksFrozen() {
-@@ -2679,11 +3293,40 @@
+@@ -2679,11 +3294,40 @@
  
      public void thunderHit(ServerLevel world, LightningBolt lightning) {
          this.setRemainingFireTicks(this.remainingFireTicks + 1);
@@ -1221,7 +1221,7 @@
      }
  
      public void onAboveBubbleCol(boolean drag) {
-@@ -2713,7 +3356,7 @@
+@@ -2713,7 +3357,7 @@
          this.resetFallDistance();
      }
  
@@ -1230,7 +1230,7 @@
          return true;
      }
  
-@@ -2818,7 +3461,7 @@
+@@ -2818,7 +3462,7 @@
      public String toString() {
          String s = this.level() == null ? "~NULL~" : this.level().toString();
  
@@ -1239,8 +1239,16 @@
      }
  
      public final boolean isInvulnerableToBase(DamageSource damageSource) {
-@@ -2852,6 +3495,26 @@
+@@ -2850,8 +3494,34 @@
+     public Entity teleport(TeleportTransition teleportTarget) {
+         Level world = this.level();
  
++        // Paper start - Fix item duplication and teleport issues
++        if ((!this.isAlive() || !this.valid) && (teleportTarget.newLevel() != world)) {
++            LOGGER.warn("Illegal Entity Teleport " + this + " to " + teleportTarget.newLevel() + ":" + teleportTarget.position(), new Throwable());
++            return null;
++        }
++        // Paper end - Fix item duplication and teleport issues
          if (world instanceof ServerLevel worldserver) {
              if (!this.isRemoved()) {
 +                // CraftBukkit start
@@ -1266,8 +1274,15 @@
                  ServerLevel worldserver1 = teleportTarget.newLevel();
                  boolean flag = worldserver1.dimension() != worldserver.dimension();
  
-@@ -2920,8 +3583,12 @@
+@@ -2918,10 +3588,19 @@
+             gameprofilerfiller.pop();
+             return null;
          } else {
++            // Paper start - Fix item duplication and teleport issues
++            if (this instanceof Leashable leashable) {
++                leashable.dropLeash(); // Paper drop lead
++            }
++            // Paper end - Fix item duplication and teleport issues
              entity.restoreFrom(this);
              this.removeAfterChangingDimensions();
 +            // CraftBukkit start - Forward the CraftEntity to the new entity
@@ -1280,7 +1295,7 @@
              Iterator iterator1 = list1.iterator();
  
              while (iterator1.hasNext()) {
-@@ -2947,7 +3614,7 @@
+@@ -2947,7 +3626,7 @@
      }
  
      private void sendTeleportTransitionToRidingPlayers(TeleportTransition teleportTarget) {
@@ -1289,7 +1304,7 @@
          Iterator iterator = this.getIndirectPassengers().iterator();
  
          while (iterator.hasNext()) {
-@@ -2995,8 +3662,9 @@
+@@ -2995,8 +3674,9 @@
      }
  
      protected void removeAfterChangingDimensions() {
@@ -1300,7 +1315,7 @@
              leashable.removeLeash();
          }
  
-@@ -3006,6 +3674,20 @@
+@@ -3006,11 +3686,26 @@
          return PortalShape.getRelativePosition(portalRect, portalAxis, this.position(), this.getDimensions(this.getPose()));
      }
  
@@ -1321,7 +1336,13 @@
      public boolean canUsePortal(boolean allowVehicles) {
          return (allowVehicles || !this.isPassenger()) && this.isAlive();
      }
-@@ -3134,10 +3816,16 @@
+ 
+     public boolean canTeleport(Level from, Level to) {
++        if (!this.isAlive() || !this.valid) return false; // Paper - Fix item duplication and teleport issues
+         if (from.dimension() == Level.END && to.dimension() == Level.OVERWORLD) {
+             Iterator iterator = this.getPassengers().iterator();
+ 
+@@ -3134,10 +3829,16 @@
          return (Boolean) this.entityData.get(Entity.DATA_CUSTOM_NAME_VISIBLE);
      }
  
@@ -1341,7 +1362,7 @@
          return entity != null;
      }
  
-@@ -3187,7 +3875,7 @@
+@@ -3187,7 +3888,7 @@
      /** @deprecated */
      @Deprecated
      protected void fixupDimensions() {
@@ -1350,7 +1371,7 @@
          EntityDimensions entitysize = this.getDimensions(entitypose);
  
          this.dimensions = entitysize;
-@@ -3196,7 +3884,7 @@
+@@ -3196,7 +3897,7 @@
  
      public void refreshDimensions() {
          EntityDimensions entitysize = this.dimensions;
@@ -1359,7 +1380,7 @@
          EntityDimensions entitysize1 = this.getDimensions(entitypose);
  
          this.dimensions = entitysize1;
-@@ -3258,10 +3946,29 @@
+@@ -3258,10 +3959,29 @@
      }
  
      public final void setBoundingBox(AABB boundingBox) {
@@ -1391,7 +1412,7 @@
          return this.getDimensions(pose).eyeHeight();
      }
  
-@@ -3335,7 +4042,7 @@
+@@ -3335,7 +4055,7 @@
      }
  
      @Nullable
@@ -1400,7 +1421,7 @@
          return null;
      }
  
-@@ -3435,7 +4142,7 @@
+@@ -3435,7 +4155,7 @@
      }
  
      public boolean isControlledByLocalInstance() {
@@ -1409,7 +1430,7 @@
  
          if (entityliving instanceof Player entityhuman) {
              return entityhuman.isLocalPlayer();
-@@ -3445,7 +4152,7 @@
+@@ -3445,7 +4165,7 @@
      }
  
      public boolean isControlledByClient() {
@@ -1418,7 +1439,7 @@
  
          return entityliving != null && entityliving.isControlledByClient();
      }
-@@ -3463,7 +4170,7 @@
+@@ -3463,7 +4183,7 @@
          return new Vec3((double) f1 * d2 / (double) f3, 0.0D, (double) f2 * d2 / (double) f3);
      }
  
@@ -1427,7 +1448,7 @@
          return new Vec3(this.getX(), this.getBoundingBox().maxY, this.getZ());
      }
  
-@@ -3488,9 +4195,38 @@
+@@ -3488,9 +4208,38 @@
      public int getFireImmuneTicks() {
          return 1;
      }
@@ -1467,7 +1488,7 @@
      }
  
      public void lookAt(EntityAnchorArgument.Anchor anchorPoint, Vec3 target) {
-@@ -3551,6 +4287,11 @@
+@@ -3551,6 +4300,11 @@
                                      vec3d = vec3d.add(vec3d1);
                                      ++k1;
                                  }
@@ -1479,7 +1500,7 @@
                              }
                          }
                      }
-@@ -3613,7 +4354,7 @@
+@@ -3613,7 +4367,7 @@
          return new ClientboundAddEntityPacket(this, entityTrackerEntry);
      }
  
@@ -1488,7 +1509,7 @@
          return this.type.getDimensions();
      }
  
-@@ -3818,8 +4559,16 @@
+@@ -3818,8 +4572,16 @@
  
      @Override
      public final void setRemoved(Entity.RemovalReason reason) {
@@ -1506,7 +1527,7 @@
          }
  
          if (this.removalReason.shouldDestroy()) {
-@@ -3827,8 +4576,8 @@
+@@ -3827,8 +4589,8 @@
          }
  
          this.getPassengers().forEach(Entity::stopRiding);
@@ -1517,7 +1538,7 @@
      }
  
      public void unsetRemoved() {
-@@ -3887,7 +4636,7 @@
+@@ -3887,7 +4649,7 @@
      }
  
      public Vec3 getKnownMovement() {

paper-server/patches/sources/net/minecraft/world/entity/LivingEntity.java.patch

@@ -66,7 +66,7 @@
      public int lastHurtByPlayerTime;
      protected boolean dead;
      protected int noActionTime;
-@@ -260,7 +285,29 @@
+@@ -260,6 +285,28 @@
      protected boolean skipDropExperience;
      private final EnumMap<EquipmentSlot, Reference2ObjectMap<Enchantment, Set<EnchantmentLocationBasedEffect>>> activeLocationDependentEnchantments;
      protected float appliedScale;
@@ -79,7 +79,7 @@
 +    public boolean bukkitPickUpLoot;
 +    public org.bukkit.craftbukkit.entity.CraftLivingEntity getBukkitLivingEntity() { return (org.bukkit.craftbukkit.entity.CraftLivingEntity) super.getBukkitEntity(); } // Paper
 +    public boolean silentDeath = false; // Paper - mark entity as dying silently for cancellable death event
- 
++
 +    @Override
 +    public float getBukkitYaw() {
 +        return this.getYHeadRot();
@@ -92,10 +92,9 @@
 +        ++this.noActionTime; // Above all the floats
 +    }
 +    // Spigot end
-+
+ 
      protected LivingEntity(EntityType<? extends LivingEntity> type, Level world) {
          super(type, world);
-         this.lastHandItemStacks = NonNullList.withSize(2, ItemStack.EMPTY);
 @@ -276,7 +323,9 @@
          this.activeLocationDependentEnchantments = new EnumMap(EquipmentSlot.class);
          this.appliedScale = 1.0F;
@@ -783,9 +782,9 @@
 +                // Paper start
 +                org.bukkit.event.entity.EntityDeathEvent deathEvent = this.dropAllDeathLoot(worldserver, damageSource);
 +                if (deathEvent == null || !deathEvent.isCancelled()) {
-+                    if (entityliving != null) {
++                    //if (entityliving != null) { // Paper - Fix item duplication and teleport issues; moved to be run earlier in #dropAllDeathLoot before destroying the drop items in CraftEventFactory#callEntityDeathEvent
-+                        entityliving.awardKillScore(this, damageSource);
++                    //    entityliving.awardKillScore(this, damageSource);
-+                    }
++                    //}
 +                    // Paper start - clear equipment if event is not cancelled
 +                    if (this instanceof Mob) {
 +                        for (EquipmentSlot slot : this.clearedEquipmentSlots) {
@@ -860,7 +859,7 @@
                      this.level().addFreshEntity(entityitem);
                  }
              }
-@@ -1527,27 +1854,55 @@
+@@ -1527,27 +1854,60 @@
          }
      }
  
@@ -883,8 +882,13 @@
              this.dropCustomDeathLoot(world, damageSource, flag);
 +            this.clearEquipmentSlots = prev; // Paper
          }
-+        // CraftBukkit start - Call death event
++        // CraftBukkit start - Call death event // Paper start - call advancement triggers with correct entity equipment
-+        org.bukkit.event.entity.EntityDeathEvent deathEvent = CraftEventFactory.callEntityDeathEvent(this, damageSource, this.drops); // Paper
++        org.bukkit.event.entity.EntityDeathEvent deathEvent = CraftEventFactory.callEntityDeathEvent(this, damageSource, this.drops, () -> {
++            final LivingEntity entityliving = this.getKillCredit();
++            if (entityliving != null) {
++                entityliving.awardKillScore(this, damageSource);
++            }
++        }); // Paper end
 +        this.postDeathDropItems(deathEvent); // Paper
 +        this.drops = new ArrayList<>();
 +        // CraftBukkit end
@@ -921,7 +925,7 @@
      protected void dropCustomDeathLoot(ServerLevel world, DamageSource source, boolean causedByPlayer) {}
  
      public long getLootTableSeed() {
-@@ -1612,19 +1967,35 @@
+@@ -1612,19 +1972,35 @@
      }
  
      public void knockback(double strength, double x, double z) {
@@ -964,7 +968,7 @@
          }
      }
  
-@@ -1683,6 +2054,20 @@
+@@ -1683,6 +2059,20 @@
          return new LivingEntity.Fallsounds(SoundEvents.GENERIC_SMALL_FALL, SoundEvents.GENERIC_BIG_FALL);
      }
  
@@ -985,7 +989,7 @@
      public Optional<BlockPos> getLastClimbablePos() {
          return this.lastClimbablePos;
      }
-@@ -1757,9 +2142,14 @@
+@@ -1757,9 +2147,14 @@
          int i = this.calculateFallDamage(fallDistance, damageMultiplier);
  
          if (i > 0) {
@@ -1001,7 +1005,7 @@
              return true;
          } else {
              return flag;
-@@ -1830,7 +2220,7 @@
+@@ -1830,7 +2225,7 @@
  
      protected float getDamageAfterArmorAbsorb(DamageSource source, float amount) {
          if (!source.is(DamageTypeTags.BYPASSES_ARMOR)) {
@@ -1010,7 +1014,7 @@
              amount = CombatRules.getDamageAfterAbsorb(this, amount, source, (float) this.getArmorValue(), (float) this.getAttributeValue(Attributes.ARMOR_TOUGHNESS));
          }
  
-@@ -1841,7 +2231,8 @@
+@@ -1841,7 +2236,8 @@
          if (source.is(DamageTypeTags.BYPASSES_EFFECTS)) {
              return amount;
          } else {
@@ -1020,7 +1024,7 @@
                  int i = (this.getEffect(MobEffects.DAMAGE_RESISTANCE).getAmplifier() + 1) * 5;
                  int j = 25 - i;
                  float f1 = amount * (float) j;
-@@ -1884,18 +2275,154 @@
+@@ -1884,18 +2280,154 @@
          }
      }
  
@@ -1047,7 +1051,7 @@
 +        };
 +        float freezingModifier = freezing.apply((double) f).floatValue();
 +        f += freezingModifier;
- 
++
 +        com.google.common.base.Function<Double, Double> hardHat = new com.google.common.base.Function<Double, Double>() {
 +            @Override
 +            public Double apply(Double f) {
@@ -1059,7 +1063,7 @@
 +        };
 +        float hardHatModifier = hardHat.apply((double) f).floatValue();
 +        f += hardHatModifier;
-+
+ 
 +        com.google.common.base.Function<Double, Double> blocking = new com.google.common.base.Function<Double, Double>() {
 +            @Override
 +            public Double apply(Double f) {
@@ -1184,7 +1188,7 @@
  
                  if (entity instanceof ServerPlayer) {
                      ServerPlayer entityplayer = (ServerPlayer) entity;
-@@ -1904,13 +2431,48 @@
+@@ -1904,13 +2436,48 @@
                  }
              }
  
@@ -1237,7 +1241,7 @@
      }
  
      public CombatTracker getCombatTracker() {
-@@ -1935,8 +2497,18 @@
+@@ -1935,8 +2502,18 @@
      }
  
      public final void setArrowCount(int stuckArrowCount) {
@@ -1257,7 +1261,7 @@
  
      public final int getStingerCount() {
          return (Integer) this.entityData.get(LivingEntity.DATA_STINGER_COUNT_ID);
-@@ -1999,7 +2571,7 @@
+@@ -1999,7 +2576,7 @@
                      this.playSound(soundeffect, this.getSoundVolume(), (this.random.nextFloat() - this.random.nextFloat()) * 0.2F + 1.0F);
                  }
  
@@ -1266,7 +1270,7 @@
                      this.setHealth(0.0F);
                      this.die(this.damageSources().generic());
                  }
-@@ -2182,6 +2754,12 @@
+@@ -2182,6 +2759,12 @@
  
      public abstract ItemStack getItemBySlot(EquipmentSlot slot);
  
@@ -1279,7 +1283,7 @@
      public abstract void setItemSlot(EquipmentSlot slot, ItemStack stack);
  
      public Iterable<ItemStack> getHandSlots() {
-@@ -2494,7 +3072,7 @@
+@@ -2494,7 +3077,7 @@
  
      }
  
@@ -1288,7 +1292,7 @@
          Vec3 vec3d1 = this.getRiddenInput(controllingPlayer, movementInput);
  
          this.tickRidden(controllingPlayer, vec3d1);
-@@ -2507,13 +3085,13 @@
+@@ -2507,13 +3090,13 @@
  
      }
  
@@ -1305,7 +1309,7 @@
          return this.getSpeed();
      }
  
-@@ -2571,7 +3149,7 @@
+@@ -2571,7 +3154,7 @@
              double d1 = Mth.clamp(motion.z, -0.15000000596046448D, 0.15000000596046448D);
              double d2 = Math.max(motion.y, -0.15000000596046448D);
  
@@ -1314,7 +1318,7 @@
                  d2 = 0.0D;
              }
  
-@@ -2586,7 +3164,7 @@
+@@ -2586,7 +3169,7 @@
      }
  
      protected float getFlyingSpeed() {
@@ -1323,7 +1327,7 @@
      }
  
      public float getSpeed() {
-@@ -2634,7 +3212,7 @@
+@@ -2634,7 +3217,7 @@
                  }
              }
  
@@ -1332,7 +1336,7 @@
              if (this.tickCount % 20 == 0) {
                  this.getCombatTracker().recheckStatus();
              }
-@@ -2741,7 +3319,7 @@
+@@ -2741,7 +3324,7 @@
          this.elytraAnimationState.tick();
      }
  
@@ -1341,15 +1345,14 @@
          Map<EquipmentSlot, ItemStack> map = this.collectEquipmentChanges();
  
          if (map != null) {
-@@ -2778,10 +3356,17 @@
+@@ -2778,10 +3361,17 @@
                      throw new MatchException((String) null, (Throwable) null);
              }
  
 -            ItemStack itemstack2 = itemstack1;
--
--            itemstack = this.getItemBySlot(enumitemslot);
 +            ItemStack itemstack2 = itemstack1; final ItemStack oldEquipment = itemstack2; // Paper - PlayerArmorChangeEvent - obfhelper 
-+
+ 
+-            itemstack = this.getItemBySlot(enumitemslot);
 +            itemstack = this.getItemBySlot(enumitemslot); final ItemStack newEquipment = itemstack;// Paper - PlayerArmorChangeEvent - obfhelper
              if (this.equipmentHasChanged(itemstack2, itemstack)) {
 +                // Paper start - PlayerArmorChangeEvent
@@ -1362,7 +1365,7 @@
                  if (map == null) {
                      map = Maps.newEnumMap(EquipmentSlot.class);
                  }
-@@ -2974,8 +3559,10 @@
+@@ -2974,8 +3564,10 @@
              } else if (this.isInLava() && (!this.onGround() || d3 > d4)) {
                  this.jumpInLiquid(FluidTags.LAVA);
              } else if ((this.onGround() || flag && d3 <= d4) && this.noJumpDelay == 0) {
@@ -1373,7 +1376,7 @@
              }
          } else {
              this.noJumpDelay = 0;
-@@ -3000,7 +3587,7 @@
+@@ -3000,7 +3592,7 @@
          {
              LivingEntity entityliving = this.getControllingPassenger();
  
@@ -1382,7 +1385,7 @@
                  if (this.isAlive()) {
                      this.travelRidden(entityhuman, vec3d1);
                      break label112;
-@@ -3063,6 +3650,7 @@
+@@ -3063,6 +3655,7 @@
          this.checkSlowFallDistance();
          if (!this.level().isClientSide) {
              if (!this.canGlide()) {
@@ -1390,7 +1393,7 @@
                  this.setSharedFlag(7, false);
                  return;
              }
-@@ -3113,12 +3701,26 @@
+@@ -3113,12 +3706,26 @@
          Level world = this.level();
  
          if (!(world instanceof ServerLevel worldserver)) {
@@ -1419,7 +1422,7 @@
  
                  if (i > 0 && list.size() > i - 1 && this.random.nextInt(4) == 0) {
                      int j = 0;
-@@ -3138,10 +3740,12 @@
+@@ -3138,10 +3745,12 @@
                  }
  
                  Iterator iterator1 = list.iterator();
@@ -1434,7 +1437,7 @@
                      this.doPush(entity1);
                  }
              }
-@@ -3190,9 +3794,15 @@
+@@ -3190,9 +3799,15 @@
  
      @Override
      public void stopRiding() {
@@ -1451,7 +1454,7 @@
          if (entity != null && entity != this.getVehicle() && !this.level().isClientSide) {
              this.dismountVehicle(entity);
          }
-@@ -3305,15 +3915,22 @@
+@@ -3305,15 +3920,22 @@
  
      @Override
      public boolean isPickable() {
@@ -1476,7 +1479,7 @@
      public float getYHeadRot() {
          return this.yHeadRot;
      }
-@@ -3342,7 +3959,7 @@
+@@ -3342,7 +3964,7 @@
      }
  
      public final void setAbsorptionAmount(float absorptionAmount) {
@@ -1485,7 +1488,7 @@
      }
  
      protected void internalSetAbsorptionAmount(float absorptionAmount) {
-@@ -3410,9 +4027,14 @@
+@@ -3410,9 +4032,14 @@
      }
  
      public void startUsingItem(InteractionHand hand) {
@@ -1501,7 +1504,7 @@
              this.useItem = itemstack;
              this.useItemRemaining = itemstack.getUseDuration(this);
              if (!this.level().isClientSide) {
-@@ -3483,13 +4105,49 @@
+@@ -3483,13 +4110,49 @@
                  this.releaseUsingItem();
              } else {
                  if (!this.useItem.isEmpty() && this.isUsingItem()) {
@@ -1552,7 +1555,7 @@
                  }
  
              }
-@@ -3544,12 +4202,69 @@
+@@ -3544,12 +4207,69 @@
          if (this.isUsingItem() && !this.useItem.isEmpty()) {
              Item item = this.useItem.getItem();
  
@@ -1623,7 +1626,7 @@
      public boolean isSuppressingSlidingDownLadder() {
          return this.isShiftKeyDown();
      }
-@@ -3568,12 +4283,18 @@
+@@ -3568,12 +4288,18 @@
      }
  
      public boolean randomTeleport(double x, double y, double z, boolean particleEffects) {
@@ -1644,7 +1647,7 @@
          Level world = this.level();
  
          if (world.hasChunkAt(blockposition)) {
-@@ -3592,18 +4313,43 @@
+@@ -3592,18 +4318,43 @@
              }
  
              if (flag2) {
@@ -1692,7 +1695,7 @@
                  world.broadcastEntityEvent(this, (byte) 46);
              }
  
-@@ -3613,7 +4359,7 @@
+@@ -3613,7 +4364,7 @@
                  entitycreature.getNavigation().stop();
              }
  
@@ -1701,7 +1704,7 @@
          }
      }
  
-@@ -3706,7 +4452,7 @@
+@@ -3706,7 +4457,7 @@
      }
  
      public void stopSleeping() {
@@ -1710,7 +1713,7 @@
          Level world = this.level();
  
          java.util.Objects.requireNonNull(world);
-@@ -3718,9 +4464,9 @@
+@@ -3718,9 +4469,9 @@
  
                  this.level().setBlock(blockposition, (BlockState) iblockdata.setValue(BedBlock.OCCUPIED, false), 3);
                  Vec3 vec3d = (Vec3) BedBlock.findStandUpPosition(this.getType(), this.level(), blockposition, enumdirection, this.getYRot()).orElseGet(() -> {
@@ -1722,7 +1725,7 @@
                  });
                  Vec3 vec3d1 = Vec3.atBottomCenterOf(blockposition).subtract(vec3d).normalize();
                  float f = (float) Mth.wrapDegrees(Mth.atan2(vec3d1.z, vec3d1.x) * 57.2957763671875D - 90.0D);
-@@ -3740,7 +4486,7 @@
+@@ -3740,7 +4491,7 @@
  
      @Nullable
      public Direction getBedOrientation() {
@@ -1731,7 +1734,7 @@
  
          return blockposition != null ? BedBlock.getBedOrientation(this.level(), blockposition) : null;
      }
-@@ -3905,7 +4651,7 @@
+@@ -3905,7 +4656,7 @@
      public float maxUpStep() {
          float f = (float) this.getAttributeValue(Attributes.STEP_HEIGHT);
  

paper-server/patches/sources/net/minecraft/world/entity/decoration/ArmorStand.java.patch

@@ -355,7 +355,7 @@
              itemstack = (ItemStack) this.handItems.get(i);
              if (!itemstack.isEmpty()) {
 -                Block.popResource(this.level(), this.blockPosition().above(), itemstack);
-+                this.drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asBukkitCopy(itemstack)); // CraftBukkit - add to drops
++                this.drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asCraftMirror(itemstack)); // CraftBukkit - add to drops // Paper - mirror so we can destroy it later - though this call site was safe
                  this.handItems.set(i, ItemStack.EMPTY);
              }
          }
@@ -364,7 +364,7 @@
              itemstack = (ItemStack) this.armorItems.get(i);
              if (!itemstack.isEmpty()) {
 -                Block.popResource(this.level(), this.blockPosition().above(), itemstack);
-+                this.drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asBukkitCopy(itemstack)); // CraftBukkit - add to drops
++                this.drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asCraftMirror(itemstack)); // CraftBukkit - add to drops // Paper - mirror so we can destroy it later - though this call site was safe
                  this.armorItems.set(i, ItemStack.EMPTY);
              }
          }

paper-server/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java

@@ -903,6 +903,11 @@ public class CraftEventFactory {
     }
 
     public static EntityDeathEvent callEntityDeathEvent(net.minecraft.world.entity.LivingEntity victim, DamageSource damageSource, List<org.bukkit.inventory.ItemStack> drops) {
+        // Paper start
+        return CraftEventFactory.callEntityDeathEvent(victim, damageSource, drops, com.google.common.util.concurrent.Runnables.doNothing());
+    }
+    public static EntityDeathEvent callEntityDeathEvent(net.minecraft.world.entity.LivingEntity victim, DamageSource damageSource, List<org.bukkit.inventory.ItemStack> drops, Runnable lootCheck) {
+        // Paper end
         CraftLivingEntity entity = (CraftLivingEntity) victim.getBukkitEntity();
         CraftDamageSource bukkitDamageSource = new CraftDamageSource(damageSource);
         CraftWorld world = (CraftWorld) entity.getWorld();
@@ -917,11 +922,13 @@ public class CraftEventFactory {
         playDeathSound(victim, event);
         // Paper end
         victim.expToDrop = event.getDroppedExp();
+        lootCheck.run(); // Paper - advancement triggers before destroying items
 
         for (org.bukkit.inventory.ItemStack stack : event.getDrops()) {
             if (stack == null || stack.getType() == Material.AIR || stack.getAmount() == 0) continue;
 
-            world.dropItem(entity.getLocation(), stack);
+            world.dropItem(entity.getLocation(), stack); // Paper - note: dropItem already clones due to this being bukkit -> NMS
+            if (stack instanceof CraftItemStack) stack.setAmount(0); // Paper - destroy this item - if this ever leaks due to game bugs, ensure it doesn't dupe, but don't nuke bukkit stacks of manually added items
         }
 
         return event;