Prevent Saving Bad entities to chunks

See https://github.com/PaperMC/Paper/issues/1223

Should fix Vanilla bugs

Minecraft is saving invalid entities to the chunk files.

Avoid saving bad data, and also make improvements to handle
loading these chunks. Any invalid entity will be instant killed,
so lets avoid adding it to the world...

This lets us be safer about the dupe UUID resolver too, as now
we can ignore instant killed entities and avoid risk of duplicating
an invalid entity.

This should reduce log occurrences of dupe uuid messages.

Also reduce the logging spam overall.

Spigot-Server-Patches/0336-Add-Debug-Entities-option-to-debug-dupe-uuid-issues.patch

@@ -1,31 +1,12 @@
-From 46caf77f4a0b159f721e681f44228a02b3cfeee2 Mon Sep 17 00:00:00 2001
+From fd5af731abdbb7f69e1faa16cd763c44018f643c Mon Sep 17 00:00:00 2001
 From: Aikar <aikar@aikar.co>
 Date: Sat, 21 Jul 2018 08:25:40 -0400
 Subject: [PATCH] Add Debug Entities option to debug dupe uuid issues
 
 Add -Ddebug.entities=true to your JVM flags to gain more information
 
-diff --git a/src/main/java/net/minecraft/server/ChunkRegionLoader.java b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
-index bcce5e8b7..f5b9aa561 100644
---- a/src/main/java/net/minecraft/server/ChunkRegionLoader.java
-+++ b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
-@@ -351,6 +351,14 @@ public class ChunkRegionLoader implements IChunkLoader, IAsyncChunkSaver {
- 
-             while (iterator.hasNext()) {
-                 Entity entity = (Entity) iterator.next();
-+                // Paper start
-+                if (entity.getChunkX() != chunk.locX || entity.getChunkZ() != chunk.locZ) {
-+                    LogManager.getLogger().error(entity + " is not actually in this chunk! Report this to https://github.com/PaperMC/Paper/issues/1223", new Throwable());
-+                }
-+                if ((int)Math.floor(entity.locX) >> 4 != chunk.locX || (int)Math.floor(entity.locZ) >> 4 != chunk.locZ) {
-+                    LogManager.getLogger().error(entity + " will be leaving this chunk but saved to it. Report this to https://github.com/PaperMC/Paper/issues/1223", new Throwable());
-+                }
-+                // Paper end
- 
-                 nbttagcompound1 = new NBTTagCompound();
-                 if (entity.d(nbttagcompound1)) {
 diff --git a/src/main/java/net/minecraft/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
-index 99dac412f..0d3af8cb7 100644
+index 99dac412f0..0d3af8cb77 100644
 --- a/src/main/java/net/minecraft/server/Entity.java
 +++ b/src/main/java/net/minecraft/server/Entity.java
 @@ -73,6 +73,7 @@ public abstract class Entity implements ICommandListener, KeyedObject { // Paper
@@ -37,7 +18,7 @@ index 99dac412f..0d3af8cb7 100644
  
      private static final Logger a = LogManager.getLogger();
 diff --git a/src/main/java/net/minecraft/server/WorldServer.java b/src/main/java/net/minecraft/server/WorldServer.java
-index b16324e1a..994d4bbb8 100644
+index b16324e1a2..994d4bbb84 100644
 --- a/src/main/java/net/minecraft/server/WorldServer.java
 +++ b/src/main/java/net/minecraft/server/WorldServer.java
 @@ -7,6 +7,7 @@ import com.google.common.util.concurrent.ListenableFuture;

Spigot-Server-Patches/0341-Prevent-Saving-Bad-entities-to-chunks.patch

@@ -0,0 +1,105 @@
+From 192eaaeea08d9440107cf701c7d769341386855f Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Thu, 26 Jul 2018 00:11:12 -0400
+Subject: [PATCH] Prevent Saving Bad entities to chunks
+
+See https://github.com/PaperMC/Paper/issues/1223
+
+Minecraft is saving invalid entities to the chunk files.
+
+Avoid saving bad data, and also make improvements to handle
+loading these chunks. Any invalid entity will be instant killed,
+so lets avoid adding it to the world...
+
+This lets us be safer about the dupe UUID resolver too, as now
+we can ignore instant killed entities and avoid risk of duplicating
+an invalid entity.
+
+This should reduce log occurrences of dupe uuid messages.
+
+diff --git a/src/main/java/net/minecraft/server/Chunk.java b/src/main/java/net/minecraft/server/Chunk.java
+index be0b411e5c..e5a5217429 100644
+--- a/src/main/java/net/minecraft/server/Chunk.java
++++ b/src/main/java/net/minecraft/server/Chunk.java
+@@ -897,11 +897,12 @@ public class Chunk {
+                 Map<UUID, Entity> thisChunk = new HashMap<>();
+                 for (Iterator<Entity> iterator = ((List<Entity>) entityslice).iterator(); iterator.hasNext(); ) {
+                     Entity entity = iterator.next();
++                    if (entity.dead) continue;
+                     Entity other = ((WorldServer) world).entitiesByUUID.get(entity.uniqueID);
+                     if (other == null) {
+                         other = thisChunk.get(entity.uniqueID);
+                     }
+-                    if (other != null) {
++                    if (other != null && !other.dead) {
+                         switch (mode) {
+                             case REGEN: {
+                                 entity.setUUID(UUID.randomUUID());
+diff --git a/src/main/java/net/minecraft/server/ChunkRegionLoader.java b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
+index bcce5e8b7e..bad287fca4 100644
+--- a/src/main/java/net/minecraft/server/ChunkRegionLoader.java
++++ b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
+@@ -346,11 +346,22 @@ public class ChunkRegionLoader implements IChunkLoader, IAsyncChunkSaver {
+ 
+         Iterator iterator;
+ 
++        List<Entity> toUpdate = new java.util.ArrayList<>(); // Paper
+         for (i = 0; i < chunk.getEntitySlices().length; ++i) {
+             iterator = chunk.getEntitySlices()[i].iterator();
+ 
+             while (iterator.hasNext()) {
+                 Entity entity = (Entity) iterator.next();
++                // Paper start
++                if ((int)Math.floor(entity.locX) >> 4 != chunk.locX || (int)Math.floor(entity.locZ) >> 4 != chunk.locZ) {
++                    LogManager.getLogger().warn(entity + " is not in this chunk, skipping save. This a bug fix to a vanilla bug. Do not report this to PaperMC please.");
++                    toUpdate.add(entity);
++                    continue;
++                }
++                if (entity.dead) {
++                    continue;
++                }
++                // Paper end
+ 
+                 nbttagcompound1 = new NBTTagCompound();
+                 if (entity.d(nbttagcompound1)) {
+@@ -359,6 +370,11 @@ public class ChunkRegionLoader implements IChunkLoader, IAsyncChunkSaver {
+                 }
+             }
+         }
++        // Paper start - move entities to the correct chunk
++        for (Entity entity : toUpdate) {
++            world.entityJoinedWorld(entity, false);
++        }
++        // Paper end
+ 
+         nbttagcompound.set("Entities", nbttaglist1);
+         NBTTagList nbttaglist2 = new NBTTagList();
+diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
+index 52adee8806..c2b92ad3a5 100644
+--- a/src/main/java/net/minecraft/server/World.java
++++ b/src/main/java/net/minecraft/server/World.java
+@@ -1202,7 +1202,7 @@ public abstract class World implements IBlockAccess {
+             }
+ 
+             this.getChunkAt(i, j).a(entity);
+-            this.entityList.add(entity);
++            if (!entity.dead) this.entityList.add(entity); // Paper - don't add dead entities, chunk registration may of killed it
+             this.b(entity);
+             return true;
+         }
+diff --git a/src/main/java/net/minecraft/server/WorldServer.java b/src/main/java/net/minecraft/server/WorldServer.java
+index 1244baf45a..1763d9f94d 100644
+--- a/src/main/java/net/minecraft/server/WorldServer.java
++++ b/src/main/java/net/minecraft/server/WorldServer.java
+@@ -1173,7 +1173,7 @@ public class WorldServer extends World implements IAsyncTaskHandler {
+             if (this.entitiesByUUID.containsKey(uuid)) {
+                 Entity entity1 = (Entity) this.entitiesByUUID.get(uuid);
+ 
+-                if (this.f.contains(entity1)) {
++                if (this.f.contains(entity1) || entity1.dead) { // Paper - overwrite the current dead one
+                     this.f.remove(entity1);
+                 } else {
+                     if (!(entity instanceof EntityHuman)) {
+-- 
+2.18.0
+