Compensate for allow-nether/allow-end as false; Fixes BUKKIT-3466

When either of those settings are false, the worlds are not loaded and
therefore will not be targeted for portal exits.  Existing worlds are
iterated directly to avoid defaulting to the first world if a direct
dimension match is not found.

Plugins must also specify exit from custom Bukkit worlds to comply with
original commit: https://github.com/Bukkit/CraftBukkit/commit/2dc2af0

This commit introduces a constant to clarify the dependency on the
CraftBukkit implementation of custom worlds having a dimension offset.

src/main/java/net/minecraft/server/Entity.java

@@ -1750,10 +1750,20 @@ public abstract class Entity {
             MinecraftServer minecraftserver = MinecraftServer.getServer();
             // CraftBukkit start - move logic into new function "teleportToLocation"
             // int j = this.dimension;
-            Location enter = this.getBukkitEntity().getLocation();
-            Location exit = minecraftserver.getPlayerList().calculateTarget(enter, minecraftserver.getWorldServer(i));
+            WorldServer exitWorld = null;
+            if (this.dimension < CraftWorld.CUSTOM_DIMENSION_OFFSET) { // plugins must specify exit from custom Bukkit worlds
+                // only target existing worlds (compensate for allow-nether/allow-end as false)
+                for (WorldServer world : minecraftserver.worlds) {
+                    if (world.dimension == i) {
+                        exitWorld = world;
+                    }
+                }
+            }
 
-            TravelAgent agent = (TravelAgent) ((CraftWorld) exit.getWorld()).getHandle().s();
+            Location enter = this.getBukkitEntity().getLocation();
+            Location exit = exitWorld != null ? minecraftserver.getPlayerList().calculateTarget(enter, minecraftserver.getWorldServer(i)) : null;
+
+            TravelAgent agent = exit != null ? (TravelAgent) ((CraftWorld) exit.getWorld()).getHandle().s() : null;
             EntityPortalEvent event = new EntityPortalEvent(this.getBukkitEntity(), enter, exit, agent);
             event.getEntity().getServer().getPluginManager().callEvent(event);
             if (event.isCancelled() || event.getTo() == null || !this.isAlive()) {

src/main/java/net/minecraft/server/PlayerList.java

@@ -424,23 +424,35 @@ public abstract class PlayerList {
 
     // CraftBukkit start - Replaced the standard handling of portals with a more customised method.
     public void changeDimension(EntityPlayer entityplayer, int i, TeleportCause cause) {
-        WorldServer exitWorld = this.server.getWorldServer(i);
-        Location enter = entityplayer.getBukkitEntity().getLocation();
-        Location exit = null;
-        if ((cause == TeleportCause.END_PORTAL) && (i == 0)) {
-            // THE_END -> NORMAL; use bed if available
-            exit = ((CraftPlayer) entityplayer.getBukkitEntity()).getBedSpawnLocation();
-        }
-        if (exit == null) {
-            exit = this.calculateTarget(enter, exitWorld);
+        WorldServer exitWorld = null;
+        if (entityplayer.dimension < CraftWorld.CUSTOM_DIMENSION_OFFSET) { // plugins must specify exit from custom Bukkit worlds
+            // only target existing worlds (compensate for allow-nether/allow-end as false)
+            for (WorldServer world : this.server.worlds) {
+                if (world.dimension == i) {
+                    exitWorld = world;
+                }
+            }
         }
 
-        TravelAgent agent = (TravelAgent) ((CraftWorld) exit.getWorld()).getHandle().s();
+        Location enter = entityplayer.getBukkitEntity().getLocation();
+        Location exit = null;
+        if (exitWorld != null) {
+            if ((cause == TeleportCause.END_PORTAL) && (i == 0)) {
+                // THE_END -> NORMAL; use bed if available
+                exit = ((CraftPlayer) entityplayer.getBukkitEntity()).getBedSpawnLocation();
+            }
+            if (exit == null) {
+                exit = this.calculateTarget(enter, exitWorld);
+            }
+        }
+
+        TravelAgent agent = exit != null ? (TravelAgent) ((CraftWorld) exit.getWorld()).getHandle().s() : null;
         PlayerPortalEvent event = new PlayerPortalEvent(entityplayer.getBukkitEntity(), enter, exit, agent, cause);
         Bukkit.getServer().getPluginManager().callEvent(event);
         if (event.isCancelled() || event.getTo() == null) {
             return;
         }
+
         exit = event.useTravelAgent() ? event.getPortalTravelAgent().findOrCreate(exit) : event.getTo();
         exitWorld = ((CraftWorld) exit.getWorld()).getHandle();
 

src/main/java/org/bukkit/craftbukkit/CraftServer.java

@@ -694,7 +694,7 @@ public final class CraftServer implements Server {
             converter.convert(name, new ConvertProgressUpdater(console));
         }
 
-        int dimension = 10 + console.worlds.size();
+        int dimension = CraftWorld.CUSTOM_DIMENSION_OFFSET + console.worlds.size();
         boolean used = false;
         do {
             for (WorldServer server : console.worlds) {

src/main/java/org/bukkit/craftbukkit/CraftWorld.java

@@ -49,6 +49,8 @@ import org.bukkit.plugin.messaging.StandardMessenger;
 import org.bukkit.craftbukkit.util.LongHash;
 
 public class CraftWorld implements World {
+    public static final int CUSTOM_DIMENSION_OFFSET = 10;
+
     private final WorldServer world;
     private Environment environment;
     private final CraftServer server = (CraftServer) Bukkit.getServer();