Paper/patches/server/0331-Don-t-move-existing-players-to-world-spawn.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Thu, 9 Apr 2020 21:20:33 -0400
Subject: [PATCH] Don't move existing players to world spawn

This can cause a nasty server lag the spawn chunks are not kept loaded
or they aren't finished loading yet, or if the world spawn radius is
larger than the keep loaded range.

By skipping this, we avoid potential for a large spike on server start.

== AT ==
public net.minecraft.server.level.ServerPlayer fudgeSpawnLocation(Lnet/minecraft/server/level/ServerLevel;)V

diff --git a/src/main/java/net/minecraft/server/level/ServerPlayer.java b/src/main/java/net/minecraft/server/level/ServerPlayer.java
index 965ca28a8877f5e541741c45bace7075d15a77d7..adbc8e74f0b454403bc682de11bd0342e9bb6c2c 100644
--- a/src/main/java/net/minecraft/server/level/ServerPlayer.java
+++ b/src/main/java/net/minecraft/server/level/ServerPlayer.java
@@ -419,7 +419,7 @@ public class ServerPlayer extends net.minecraft.world.entity.player.Player {
         this.server = server;
         this.stats = server.getPlayerList().getPlayerStats(this);
         this.advancements = server.getPlayerList().getPlayerAdvancements(this);
-        this.moveTo(this.adjustSpawnLocation(world, world.getSharedSpawnPos()).getBottomCenter(), 0.0F, 0.0F);
+        // this.moveTo(this.adjustSpawnLocation(world, world.getSharedSpawnPos()).getBottomCenter(), 0.0F, 0.0F); // Paper - Don't move existing players to world spawn
         this.updateOptions(clientOptions);
         this.object = null;
 
@@ -856,7 +856,7 @@ public class ServerPlayer extends net.minecraft.world.entity.player.Player {
                 position = Vec3.atCenterOf(world.getSharedSpawnPos());
             }
             this.setLevel(world);
-            this.setPos(position);
+            this.setPosRaw(position.x(), position.y(), position.z()); // Paper - don't register to chunks yet
         }
         this.gameMode.setLevel((ServerLevel) world);
     }
diff --git a/src/main/java/net/minecraft/server/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
index 29110c0b950c3073ab699d8ad1523ece2e8d3408..074f3518b060c4aa079b1d311b7fcb10d4a95981 100644
--- a/src/main/java/net/minecraft/server/players/PlayerList.java
+++ b/src/main/java/net/minecraft/server/players/PlayerList.java
@@ -227,6 +227,7 @@ public abstract class PlayerList {
         // Paper start - Entity#getEntitySpawnReason
         if (optional.isEmpty()) {
             player.spawnReason = org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.DEFAULT; // set Player SpawnReason to DEFAULT on first login
+            player.moveTo(player.adjustSpawnLocation(worldserver1, worldserver1.getSharedSpawnPos()).getBottomCenter(), 0.0F, 0.0F);
         }
         // Paper end - Entity#getEntitySpawnReason
         player.setServerLevel(worldserver1);