Paper/patches/server/0356-Move-player-to-spawn-point-if-spawn-in-unloaded-worl.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: 2277 <38501234+2277@users.noreply.github.com>
Date: Tue, 31 Mar 2020 10:33:55 +0100
Subject: [PATCH] Move player to spawn point if spawn in unloaded world

If the playerdata contains an invalid world (missing, unloaded, invalid,
etc.), spawn the player at the spawn point of the main world.

Co-authored-by: Wyatt Childers <wchilders@nearce.com>
Co-authored-by: Jake Potrebic <jake.m.potrebic@gmail.com>

diff --git a/src/main/java/net/minecraft/server/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
index 4be466a21fb1fb936e1eaa6351e30a53c7b5cbb4..5657999a85b9b9dfb48a51170d5fa3d9c37263ad 100644
--- a/src/main/java/net/minecraft/server/players/PlayerList.java
+++ b/src/main/java/net/minecraft/server/players/PlayerList.java
@@ -194,7 +194,7 @@ public abstract class PlayerList {
         }
 
         CompoundTag nbttagcompound = this.load(player);
-        ResourceKey resourcekey;
+        ResourceKey<Level> resourcekey = null; // Paper
         // CraftBukkit start - Better rename detection
         if (nbttagcompound != null && nbttagcompound.contains("bukkit")) {
             CompoundTag bukkit = nbttagcompound.getCompound("bukkit");
@@ -202,15 +202,42 @@ public abstract class PlayerList {
         }
         // CraftBukkit end
 
+        // Paper start - move logic in Entity to here, to use bukkit supplied world UUID & reset to main world spawn if no valid world is found
+        boolean invalidPlayerWorld = false;
+        bukkitData: if (nbttagcompound != null) {
+            // The main way for bukkit worlds to store the world is the world UUID despite mojang adding custom worlds
+            final org.bukkit.World bWorld;
+            if (nbttagcompound.contains("WorldUUIDMost") && nbttagcompound.contains("WorldUUIDLeast")) {
+                bWorld = org.bukkit.Bukkit.getServer().getWorld(new UUID(nbttagcompound.getLong("WorldUUIDMost"), nbttagcompound.getLong("WorldUUIDLeast")));
+            } else if (nbttagcompound.contains("world", net.minecraft.nbt.Tag.TAG_STRING)) { // Paper - legacy bukkit world name
+                bWorld = org.bukkit.Bukkit.getServer().getWorld(nbttagcompound.getString("world"));
+            } else {
+                break bukkitData; // if neither of the bukkit data points exist, proceed to the vanilla migration section
+            }
+            if (bWorld != null) {
+                resourcekey = ((CraftWorld) bWorld).getHandle().dimension();
+            } else {
+                resourcekey = Level.OVERWORLD;
+                invalidPlayerWorld = true;
+            }
+        }
+        if (resourcekey == null) { // only run the vanilla logic if we haven't found a world from the bukkit data
+        // Below is the vanilla way of getting the dimension, this is for migration from vanilla servers
+        // Paper end
         if (nbttagcompound != null) {
             DataResult<ResourceKey<Level>> dataresult = DimensionType.parseLegacy(new Dynamic(NbtOps.INSTANCE, nbttagcompound.get("Dimension"))); // CraftBukkit - decompile error
             Logger logger = PlayerList.LOGGER;
 
             Objects.requireNonNull(logger);
-            resourcekey = (ResourceKey) dataresult.resultOrPartial(logger::error).orElse(player.serverLevel().dimension()); // CraftBukkit - SPIGOT-7507: If no dimension, fall back to existing dimension loaded from "WorldUUID", which in turn defaults to World.OVERWORLD
+            // Paper start - reset to main world spawn if no valid world is found
+            final Optional<ResourceKey<Level>> result = dataresult.resultOrPartial(logger::error);
+            invalidPlayerWorld = result.isEmpty();
+            resourcekey = result.orElse(Level.OVERWORLD);
+            // Paper end
         } else {
-            resourcekey = player.serverLevel().dimension(); // CraftBukkit - SPIGOT-7507: If no dimension, fall back to existing dimension loaded from "WorldUUID", which in turn defaults to World.OVERWORLD
+            resourcekey = Level.OVERWORLD; // Paper - revert to vanilla default main world, this isn't an "invalid world" since no player data existed
         }
+        } // Paper
 
         ResourceKey<Level> resourcekey1 = resourcekey;
         ServerLevel worldserver = this.server.getLevel(resourcekey1);
@@ -219,6 +246,7 @@ public abstract class PlayerList {
         if (worldserver == null) {
             PlayerList.LOGGER.warn("Unknown respawn dimension {}, defaulting to overworld", resourcekey1);
             worldserver1 = this.server.overworld();
+            invalidPlayerWorld = true; // Paper - reset to main world if no world with parsed value is found
         } else {
             worldserver1 = worldserver;
         }
@@ -226,6 +254,10 @@ public abstract class PlayerList {
         // Paper start - Entity#getEntitySpawnReason
         if (nbttagcompound == null) {
             player.spawnReason = org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.DEFAULT; // set Player SpawnReason to DEFAULT on first login
+            // Paper start - reset to main world spawn if first spawn or invalid world
+        }
+        if (nbttagcompound == null || invalidPlayerWorld) {
+            // Paper end - reset to main world spawn if first spawn or invalid world
             player.fudgeSpawnLocation(worldserver1); // Paper - Don't move existing players to world spawn
         }
         // Paper end - Entity#getEntitySpawnReason
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index b40eed864faf11962efc1e0df417074eb8737c6b..71b499843b25f78491ab2f7dad97523b9facd77c 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -2324,27 +2324,8 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
             }
             // CraftBukkit end
 
-            // CraftBukkit start - Reset world
-            if (this instanceof ServerPlayer) {
-                Server server = Bukkit.getServer();
-                org.bukkit.World bworld = null;
-
-                // TODO: Remove World related checks, replaced with WorldUID
-                String worldName = nbt.getString("world");
-
-                if (nbt.contains("WorldUUIDMost") && nbt.contains("WorldUUIDLeast")) {
-                    UUID uid = new UUID(nbt.getLong("WorldUUIDMost"), nbt.getLong("WorldUUIDLeast"));
-                    bworld = server.getWorld(uid);
-                } else {
-                    bworld = server.getWorld(worldName);
-                }
-
-                if (bworld == null) {
-                    bworld = ((org.bukkit.craftbukkit.CraftServer) server).getServer().getLevel(Level.OVERWORLD).getWorld();
-                }
-
-                ((ServerPlayer) this).setLevel(bworld == null ? null : ((CraftWorld) bworld).getHandle());
-            }
+            // CraftBukkit start
+            // Paper - move world parsing/loading to PlayerList#placeNewPlayer
             this.getBukkitEntity().readBukkitValues(nbt);
             if (nbt.contains("Bukkit.invisible")) {
                 boolean bukkitInvisible = nbt.getBoolean("Bukkit.invisible");