Paper/patches/server/0371-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 66a39d00c23bf6bced8ea9c177d84d1409cd2c11..5c5d1e387ea00a17db99b3ef1f68eede01b09789 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
         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
             player.fudgeSpawnLocation(worldserver1); // only move to spawn on first login, otherwise, stay where you are....
         }
         // Paper end
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 04635faeb265852df7ec3ea9b04c8ae24c2fcd58..b2dc3729a8312179d219bd93a755729c86f4dece 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -2337,27 +2337,8 @@ 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");