Paper/Spigot-Server-Patches/0272-Fix-CraftEntity-hashCode.patch

From fd9f7d8ba57935af3e3126cc41e5910ac3bd9f7f Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sun, 10 Jun 2018 20:20:15 -0400
Subject: [PATCH] Fix CraftEntity hashCode

hashCodes are not allowed to change, however bukkit used a value
that does change, the entityId.

When an entity is teleported dimensions, the entity reference is
replaced with a new one with a new entity ID.

For hashCode, we can simply use the UUID's hashCode to keep
the hashCode from changing.

equals() is ok to use getEntityId() because equals() should only
be true if both the left and right are the same reference.

Since entity ids can not duplicate during runtime, this
check is essentially the same as this.getHandle() == other.getHandle()

However, replaced it too to make it clearer of intent.

diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
index 2801e34f6b..6af229ce2e 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -535,14 +535,15 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
             return false;
         }
         final CraftEntity other = (CraftEntity) obj;
-        return (this.getEntityId() == other.getEntityId());
+        return (this.getHandle() == other.getHandle()); // Paper - while logically the same, this is clearer
     }
 
+    // Paper - Fix hashCode. entity ID's are not static.
+    // A CraftEntity can change reference to a new entity with a new ID, and hash codes should never change
     @Override
     public int hashCode() {
-        int hash = 7;
-        hash = 29 * hash + this.getEntityId();
-        return hash;
+        return getUniqueId().hashCode();
+        // Paper end
     }
 
     public void setMetadata(String metadataKey, MetadataValue newMetadataValue) {
-- 
2.18.0