Paper/patches/server/0203-Fix-CraftEntity-hashCode.patch

From 0000000000000000000000000000000000000000 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 41753b72ac6fdf0314d60dbe1ffb60e79b3e4af8..e6b75dfa1a59c9f1f6afde7b4538abf8d51b7261 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -807,14 +807,15 @@ 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
     }
 
     @Override