From 2df6c84b94bf4d4c4e2b28e8b59c479128c63d57 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 28 Jul 2018 12:18:27 -0400
Subject: [PATCH] Ignore Dead Entities in entityList iteration

A spigot change delays removal of entities from the entity list.
This causes a change in behavior from Vanilla where getEntities type
methods will return dead entities that they shouldn't otherwise be doing.

This will ensure that dead entities are skipped from iteration since
they shouldn't of been in the list in the first place.

diff --git a/src/main/java/com/destroystokyo/paper/PaperCommand.java b/src/main/java/com/destroystokyo/paper/PaperCommand.java
index 56700fc59..9b9c8361e 100644
--- a/src/main/java/com/destroystokyo/paper/PaperCommand.java
+++ b/src/main/java/com/destroystokyo/paper/PaperCommand.java
@@ -172,6 +172,7 @@ public class PaperCommand extends Command {
                 List<Entity> entities = world.entityList;
                 entities.forEach(e -> {
                     MinecraftKey key = e.getMinecraftKey();
+                    if (e.shouldBeRemoved) return; // Paper
 
                     MutablePair<Integer, Map<ChunkCoordIntPair, Integer>> info = list.computeIfAbsent(key, k -> MutablePair.of(0, Maps.newHashMap()));
                     ChunkCoordIntPair chunk = new ChunkCoordIntPair(e.getChunkX(), e.getChunkZ());
diff --git a/src/main/java/net/minecraft/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index 8fa36cd65..0de0dc293 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -123,6 +123,7 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
     protected boolean F;
     private boolean az;
     public boolean dead;
+    public boolean shouldBeRemoved; // Paper
     public float width;
     public float length;
     public float J;
diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
index 965a598db..2aa4946c7 100644
--- a/src/main/java/net/minecraft/server/World.java
+++ b/src/main/java/net/minecraft/server/World.java
@@ -1112,6 +1112,7 @@ public abstract class World implements IEntityAccess, GeneratorAccess, IIBlockAc
         }
 
         entity.valid = true; // CraftBukkit
+        entity.shouldBeRemoved = false; // Paper - shouldn't be removed after being re-added
         new com.destroystokyo.paper.event.entity.EntityAddToWorldEvent(entity.getBukkitEntity()).callEvent(); // Paper - fire while valid
     }
 
@@ -1180,6 +1181,7 @@ public abstract class World implements IEntityAccess, GeneratorAccess, IIBlockAc
         if (entity.inChunk && this.isChunkLoaded(i, j, true)) {
             this.getChunkAt(i, j).b(entity);
         }
+        entity.shouldBeRemoved = true; // Paper
 
         if (!guardEntityList) { // Spigot - It will get removed after the tick if we are ticking // Paper - always remove from current chunk above
         // CraftBukkit start - Decrement loop variable field if we've already ticked this entity
@@ -2390,6 +2392,7 @@ public abstract class World implements IEntityAccess, GeneratorAccess, IIBlockAc
 
         while (iterator.hasNext()) {
             Entity entity = (Entity) iterator.next();
+            if (entity.shouldBeRemoved) continue; // Paper
 
             if (oclass.isAssignableFrom(entity.getClass()) && predicate.test((T) entity)) {
                 arraylist.add(entity);
@@ -2476,6 +2479,7 @@ public abstract class World implements IEntityAccess, GeneratorAccess, IIBlockAc
 
         while (iterator.hasNext()) {
             Entity entity = (Entity) iterator.next();
+            if (entity.shouldBeRemoved) continue; // Paper
             // CraftBukkit start - Split out persistent check, don't apply it to special persistent mobs
             if (entity instanceof EntityInsentient) {
                 EntityInsentient entityinsentient = (EntityInsentient) entity;
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
index be8cc2510..a99aabc40 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
@@ -618,6 +618,7 @@ public class CraftWorld implements World {
         for (Object o : world.entityList) {
             if (o instanceof net.minecraft.server.Entity) {
                 net.minecraft.server.Entity mcEnt = (net.minecraft.server.Entity) o;
+                if (mcEnt.shouldBeRemoved) continue; // Paper
                 Entity bukkitEntity = mcEnt.getBukkitEntity();
 
                 // Assuming that bukkitEntity isn't null
@@ -636,6 +637,7 @@ public class CraftWorld implements World {
         for (Object o : world.entityList) {
             if (o instanceof net.minecraft.server.Entity) {
                 net.minecraft.server.Entity mcEnt = (net.minecraft.server.Entity) o;
+                if (mcEnt.shouldBeRemoved) continue; // Paper
                 Entity bukkitEntity = mcEnt.getBukkitEntity();
 
                 // Assuming that bukkitEntity isn't null
@@ -660,6 +662,7 @@ public class CraftWorld implements World {
 
         for (Object entity: world.entityList) {
             if (entity instanceof net.minecraft.server.Entity) {
+                if (((net.minecraft.server.Entity) entity).shouldBeRemoved) continue; // Paper
                 Entity bukkitEntity = ((net.minecraft.server.Entity) entity).getBukkitEntity();
 
                 if (bukkitEntity == null) {
@@ -682,6 +685,7 @@ public class CraftWorld implements World {
 
         for (Object entity: world.entityList) {
             if (entity instanceof net.minecraft.server.Entity) {
+                if (((net.minecraft.server.Entity) entity).shouldBeRemoved) continue; // Paper
                 Entity bukkitEntity = ((net.minecraft.server.Entity) entity).getBukkitEntity();
 
                 if (bukkitEntity == null) {
-- 
2.19.1