Fixed a bug causing the entity modifier to always lookup the same world

The entity modifier would try to cache each equivalent converter by its
specific type - i.e. whether or not it converts entities or watchable
collections - but this isn't enough to distinguish entity modifiers 
as they store a hidden reference to the world the entity is supposed 
to be occupying. 

Thus, after the first entity modifier is used for "world", it would 
be subsequently cached for every world ("world_nether", "world_end", 
etc.). The end result was that entity modifiers would only work for 
one world.

This patch fixes this problem by adding a proper equals() method to
the entity equivalent converter class, along with all the other 
equvialent converter classes, in case it should prove to become useful
in the future.

ProtocolLib/src/main/java/com/comphenix/protocol/reflect/StructureModifier.java

@@ -28,6 +28,7 @@ import java.util.concurrent.ConcurrentHashMap;
 import com.comphenix.protocol.reflect.compiler.BackgroundCompiler;
 import com.comphenix.protocol.reflect.instances.DefaultInstances;
 import com.google.common.base.Function;
+import com.google.common.base.Objects;
 import com.google.common.collect.ImmutableList;
 
 /**
@@ -394,23 +395,13 @@ public class StructureModifier<TField> {
 		result = result.withTarget(target);
 		
 		// And the converter, if it's needed
-		if (!sameConverter(result.converter, converter)) {
+		if (!Objects.equal(result.converter, converter)) {
 			result = result.withConverter(converter);
 		}
 		
 		return result;
 	}
 	
-	private boolean sameConverter(EquivalentConverter<?> a, EquivalentConverter<?> b) {
-		// Compare the converter types
-		if (a == null)
-			return b == null;
-		else if (b == null)
-			return false;
-		else
-			return a.getSpecificType().equals(b.getSpecificType());
-	}
-	
 	/**
 	 * Retrieves the common type of each field.
 	 * @return Common type of each field.

ProtocolLib/src/main/java/com/comphenix/protocol/wrappers/BukkitConverters.java

@@ -36,6 +36,7 @@ import com.comphenix.protocol.reflect.instances.DefaultInstances;
 import com.comphenix.protocol.utility.MinecraftReflection;
 import com.comphenix.protocol.wrappers.nbt.NbtBase;
 import com.comphenix.protocol.wrappers.nbt.NbtFactory;
+import com.google.common.base.Objects;
 
 /**
  * Contains several useful equivalent converters for normal Bukkit types.
@@ -58,12 +59,104 @@ public class BukkitConverters {
 		}
 	}
 	
+	/**
+	 * Represents a typical equivalence converter.
+	 * 
+	 * @author Kristian
+	 * @param <T> - type that can be converted.
+	 */
+	private static abstract class IgnoreNullConverter<TType> implements EquivalentConverter<TType> {
+		public final Object getGeneric(Class<?> genericType, TType specific) {
+			if (specific != null)
+				return getGenericValue(genericType, specific);
+			else
+				return null;
+		}
+		
+		/**
+		 * Retrieve a copy of the actual generic value.
+		 * @param genericType - generic type.
+		 * @param specific - the specific type-
+		 * @return A copy of the specific type.
+		 */
+		protected abstract Object getGenericValue(Class<?> genericType, TType specific);
+		
+		@Override
+		public final TType getSpecific(Object generic) {
+			if (generic != null)
+				return getSpecificValue(generic);
+			else
+				return null;
+		}
+		
+		/**
+		 * Retrieve a copy of the specific type using an instance of the generic type.
+		 * @param generic - generic type.
+		 * @return A copy of the specific type.
+		 */
+		protected abstract TType getSpecificValue(Object generic);
+		
+		@Override
+		public boolean equals(Object obj) {
+			// Very short
+			if (this == obj)
+				return true;
+			if (obj == null)
+				return false;
+			
+			// See if they're equivalent
+			if (obj instanceof EquivalentConverter) {
+				@SuppressWarnings("rawtypes")
+				EquivalentConverter other = (EquivalentConverter) obj;
+				return Objects.equal(this.getSpecificType(), other.getSpecificType());
+			}
+			return false;
+		}
+	}
+	
+	/**
+	 * Represents a converter that is only valid in a given world.
+	 * 
+	 * @author Kristian
+	 * @param <TType> - instance types it converts.
+	 */
+	private static abstract class WorldSpecificConverter<TType> extends IgnoreNullConverter<TType> {
+		protected World world;
+
+		/**
+		 * Initialize a new world-specificn converter.
+		 * @param world - the given world.
+		 */
+		public WorldSpecificConverter(World world) {
+			super();
+			this.world = world;
+		}
+
+		@Override
+		public boolean equals(Object obj) {
+			// More shortcuts
+			if (obj == this)
+				return true;
+			if (obj == null)
+				return false;
+			
+			// Add another constraint
+			if (obj instanceof WorldSpecificConverter && super.equals(obj)) {
+				@SuppressWarnings("rawtypes")
+				WorldSpecificConverter other = (WorldSpecificConverter) obj;
+				
+				return Objects.equal(world, other.world);
+			}
+			return false;
+		}
+	}
+	
 	public static <T> EquivalentConverter<List<T>> getListConverter(final Class<?> genericItemType, final EquivalentConverter<T> itemConverter) {
 		// Convert to and from the wrapper
-		return getIgnoreNull(new EquivalentConverter<List<T>>() {
+		return new IgnoreNullConverter<List<T>>() {
 				@SuppressWarnings("unchecked")
 				@Override
-				public List<T> getSpecific(Object generic) {
+				protected List<T> getSpecificValue(Object generic) {
 					if (generic instanceof Collection) {
 						List<T> items = new ArrayList<T>();
 					
@@ -83,7 +176,7 @@ public class BukkitConverters {
 
 				@SuppressWarnings("unchecked")
 				@Override
-				public Object getGeneric(Class<?> genericType, List<T> specific) {
+				protected Object getGenericValue(Class<?> genericType, List<T> specific) {
 					Collection<Object> newContainer = (Collection<Object>) DefaultInstances.DEFAULT.getDefault(genericType);
 					
 					// Convert each object
@@ -105,8 +198,7 @@ public class BukkitConverters {
 					Class<?> dummy = List.class;
 					return (Class<List<T>>) dummy;
 				}
-			}
+			};
-		);
 	}
 	
 	/**
@@ -114,13 +206,13 @@ public class BukkitConverters {
 	 * @return A watchable object converter.
 	 */
 	public static EquivalentConverter<WrappedWatchableObject> getWatchableObjectConverter() {
-		return getIgnoreNull(new EquivalentConverter<WrappedWatchableObject>() {
+		return new IgnoreNullConverter<WrappedWatchableObject>() {
 			@Override
-			public Object getGeneric(Class<?> genericType, WrappedWatchableObject specific) {
+			protected Object getGenericValue(Class<?> genericType, WrappedWatchableObject specific) {
 				return specific.getHandle();
 			}
 			
-			public WrappedWatchableObject getSpecific(Object generic) {
+			protected WrappedWatchableObject getSpecificValue(Object generic) {
 				if (MinecraftReflection.isWatchableObject(generic))
 					return new WrappedWatchableObject(generic);
 				else if (generic instanceof WrappedWatchableObject)
@@ -133,7 +225,7 @@ public class BukkitConverters {
 			public Class<WrappedWatchableObject> getSpecificType() {
 				return WrappedWatchableObject.class;
 			}
-		});
+		};
 	}
 	
 	/**
@@ -141,14 +233,14 @@ public class BukkitConverters {
 	 * @return A DataWatcher converter.
 	 */
 	public static EquivalentConverter<WrappedDataWatcher> getDataWatcherConverter() {
-		return getIgnoreNull(new EquivalentConverter<WrappedDataWatcher>() {
+		return new IgnoreNullConverter<WrappedDataWatcher>() {
 			@Override
-			public Object getGeneric(Class<?> genericType, WrappedDataWatcher specific) {
+			protected Object getGenericValue(Class<?> genericType, WrappedDataWatcher specific) {
 				return specific.getHandle();
 			}
 			
 			@Override
-			public WrappedDataWatcher getSpecific(Object generic) {
+			protected WrappedDataWatcher getSpecificValue(Object generic) {
 				if (MinecraftReflection.isDataWatcher(generic))
 					return new WrappedDataWatcher(generic);
 				else if (generic instanceof WrappedDataWatcher)
@@ -161,7 +253,7 @@ public class BukkitConverters {
 			public Class<WrappedDataWatcher> getSpecificType() {
 				return WrappedDataWatcher.class;
 			}
-		});
+		};
 	}
 	
 	/**
@@ -173,9 +265,9 @@ public class BukkitConverters {
 		if (!hasWorldType)
 			return null;
 		
-		return getIgnoreNull(new EquivalentConverter<WorldType>() {
+		return new IgnoreNullConverter<WorldType>() {
 			@Override
-			public Object getGeneric(Class<?> genericType, WorldType specific) {
+			protected Object getGenericValue(Class<?> genericType, WorldType specific) {
 				try {
 					if (worldTypeGetType == null)
 						worldTypeGetType = MinecraftReflection.getWorldTypeClass().getMethod("getType", String.class);
@@ -189,7 +281,7 @@ public class BukkitConverters {
 			}
 
 			@Override
-			public WorldType getSpecific(Object generic) {
+			protected WorldType getSpecificValue(Object generic) {
 				try {
 					if (worldTypeName == null)
 						worldTypeName = MinecraftReflection.getWorldTypeClass().getMethod("name");
@@ -207,7 +299,7 @@ public class BukkitConverters {
 			public Class<WorldType> getSpecificType() {
 				return WorldType.class;
 			}
-		});
+		};
 	}
 	
 	/**
@@ -215,14 +307,14 @@ public class BukkitConverters {
 	 * @return An equivalent converter for NBT.
 	 */
 	public static EquivalentConverter<NbtBase<?>> getNbtConverter() {
-		return getIgnoreNull(new EquivalentConverter<NbtBase<?>>() {
+		return new IgnoreNullConverter<NbtBase<?>>() {
 			@Override
-			public Object getGeneric(Class<?> genericType, NbtBase<?> specific) {
+			protected Object getGenericValue(Class<?> genericType, NbtBase<?> specific) {
 				return NbtFactory.fromBase(specific).getHandle();
 			}
 			
 			@Override
-			public NbtBase<?> getSpecific(Object generic) {
+			protected NbtBase<?> getSpecificValue(Object generic) {
 				return NbtFactory.fromNMS(generic);
 			}
 			
@@ -233,7 +325,7 @@ public class BukkitConverters {
 				Class<?> dummy = NbtBase.class;
 				return (Class<NbtBase<?>>) dummy;
 			}
-		});
+		};
 	}
 	
 	/**
@@ -242,27 +334,25 @@ public class BukkitConverters {
 	 * @return A converter between the underlying NMS entity and Bukkit's wrapper.
 	 */
 	public static EquivalentConverter<Entity> getEntityConverter(World world) {
-		final World container = world;
 		final WeakReference<ProtocolManager> managerRef = 
 				new WeakReference<ProtocolManager>(ProtocolLibrary.getProtocolManager());
 
-		return getIgnoreNull(new EquivalentConverter<Entity>() {
+		return new WorldSpecificConverter<Entity>(world) {
-			
 			@Override
-			public Object getGeneric(Class<?> genericType, Entity specific) {
+			public Object getGenericValue(Class<?> genericType, Entity specific) {
 				// Simple enough
 				return specific.getEntityId();
 			}
 			
 			@Override
-			public Entity getSpecific(Object generic) {
+			public Entity getSpecificValue(Object generic) {
 				try {
 					Integer id = (Integer) generic;
 					ProtocolManager manager = managerRef.get();
 					
-					// Use the 
+					// Use the entity ID to get a reference to the entity
 					if (id != null && manager != null) {
-						return manager.getEntityFromID(container, id);
+						return manager.getEntityFromID(world, id);
 					} else {
 						return null;
 					}
@@ -276,7 +366,7 @@ public class BukkitConverters {
 			public Class<Entity> getSpecificType() {
 				return Entity.class;
 			}
-		});
+		};
 	}
 	
 	/**
@@ -284,13 +374,14 @@ public class BukkitConverters {
 	 * @return Item stack converter.
 	 */
 	public static EquivalentConverter<ItemStack> getItemStackConverter() {
-		return getIgnoreNull(new EquivalentConverter<ItemStack>() {
+		return new IgnoreNullConverter<ItemStack>() {
-			public Object getGeneric(Class<?> genericType, ItemStack specific) {
+			@Override
+			protected Object getGenericValue(Class<?> genericType, ItemStack specific) {
 				return MinecraftReflection.getMinecraftItemStack(specific);
 			}
 			
 			@Override
-			public ItemStack getSpecific(Object generic) {
+			protected ItemStack getSpecificValue(Object generic) {
 				return MinecraftReflection.getBukkitItemStack(generic);
 			}
 			
@@ -298,7 +389,7 @@ public class BukkitConverters {
 			public Class<ItemStack> getSpecificType() {
 				return ItemStack.class;
 			}
-		});
+		};
 	}
 	
 	/**
@@ -308,20 +399,15 @@ public class BukkitConverters {
 	 */
 	public static <TType> EquivalentConverter<TType> getIgnoreNull(final EquivalentConverter<TType> delegate) {
 		// Automatically wrap all parameters to the delegate with a NULL check
-		return new EquivalentConverter<TType>() {
+		return new IgnoreNullConverter<TType>() {
-			public Object getGeneric(Class<?> genericType, TType specific) {
+			@Override
-				if (specific != null)
+			public Object getGenericValue(Class<?> genericType, TType specific) {
-					return delegate.getGeneric(genericType, specific);
+				return delegate.getGeneric(genericType, specific);
-				else
-					return null;
 			}
 			
 			@Override
-			public TType getSpecific(Object generic) {
+			public TType getSpecificValue(Object generic) {
-				if (generic != null)
+				return delegate.getSpecific(generic);
-					return delegate.getSpecific(generic);
-				else
-					return null;
 			}
 			
 			@Override