From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: wangxyper <wangxyper@163.com>
Date: Mon, 9 Jan 2023 12:40:56 +0800
Subject: [PATCH] Hearse: Fix some problems in ItemEntity

Original license: MIT
Original project: https://github.com/NaturalCodeClub/HearseRewrite

diff --git a/src/main/java/co/earthme/hearse/HearseConfig.java b/src/main/java/co/earthme/hearse/HearseConfig.java
index 912da4787f83f656da67e9533b60183c17e6c345..0a1de52bcdf675b9bfcbf14d39959818a7a0cbbb 100644
--- a/src/main/java/co/earthme/hearse/HearseConfig.java
+++ b/src/main/java/co/earthme/hearse/HearseConfig.java
@@ -1,4 +1,5 @@
 package co.earthme.hearse;
 
 public class HearseConfig {
+
 }
diff --git a/src/main/java/net/minecraft/world/entity/item/ItemEntity.java b/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
index c58496c84b2b3f86890050813041fa49711f3a01..3e8b68b4390a6086b1b1983fe6f8b545c2847ef8 100644
--- a/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
+++ b/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
@@ -4,6 +4,8 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Objects;
 import java.util.UUID;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 import javax.annotation.Nullable;
 import net.minecraft.world.damagesource.DamageSource;
 import net.minecraft.world.entity.Entity;
@@ -239,21 +241,24 @@ public class ItemEntity extends Entity {
         this.setDeltaMovement(vec3d.x * 0.949999988079071D, vec3d.y + (double) (vec3d.y < 0.05999999865889549D ? 5.0E-4F : 0.0F), vec3d.z * 0.949999988079071D);
     }
 
+    private final Lock mergeLock = new ReentrantLock();
+
     private void mergeWithNeighbours() {
-        if (this.isMergable()) {
-            // Spigot start
-            double radius = level.spigotConfig.itemMerge;
-            List<ItemEntity> list = this.level.getEntitiesOfClass(ItemEntity.class, this.getBoundingBox().inflate(radius, radius - 0.5D, radius), (entityitem) -> {
-                // Spigot end
-                return entityitem != this && entityitem.isMergable();
-            });
-            Iterator iterator = list.iterator();
-
-            while (iterator.hasNext()) {
-                ItemEntity entityitem = (ItemEntity) iterator.next();
-
-                if (entityitem.isMergable()) {
-                    // Paper Start - Fix items merging through walls
+        if (!this.mergeLock.tryLock()){
+            return;
+        }
+        try {
+            if (this.isMergable()) {
+                // Spigot start
+                double radius = level.spigotConfig.itemMerge;
+                List<ItemEntity> list = this.level.getEntitiesOfClass(ItemEntity.class, this.getBoundingBox().inflate(radius, radius - 0.5D, radius), (entityitem) -> {
+                    // Spigot end
+                    return entityitem != this && entityitem.isMergable();
+                });
+
+                for (ItemEntity entityitem : list) {
+                    if (entityitem.isMergable()) {
+                        // Paper Start - Fix items merging through walls
                         if (this.level.paperConfig().fixes.fixItemsMergingThroughWalls) {
                             // Pufferfish start - skip the allocations
                             /*
@@ -263,17 +268,19 @@ public class ItemEntity extends Entity {
                             if (rayTraceResult.getType() == net.minecraft.world.phys.HitResult.Type.BLOCK) continue;
                              */
                             if (level.rayTraceDirect(this.position(), entityitem.position(), net.minecraft.world.phys.shapes.CollisionContext.of(this)) ==
-                                net.minecraft.world.phys.HitResult.Type.BLOCK) continue;
+                                    net.minecraft.world.phys.HitResult.Type.BLOCK) continue;
                             // Pufferfish end
                         }
-                    // Paper End
-                    this.tryToMerge(entityitem);
-                    if (this.isRemoved()) {
-                        break;
+                        // Paper End
+                        this.tryToMerge(entityitem);
+                        if (this.isRemoved()) {
+                            break;
+                        }
                     }
                 }
             }
-
+        }finally {
+            this.mergeLock.unlock();
         }
     }