Don't overwrite an existing player injector in net login.

ProtocolLib/src/main/java/com/comphenix/protocol/injector/PacketFilterManager.java

@@ -56,6 +56,7 @@ import com.comphenix.protocol.injector.packet.PacketInjectorBuilder;
 import com.comphenix.protocol.injector.packet.PacketRegistry;
 import com.comphenix.protocol.injector.player.PlayerInjectionHandler;
 import com.comphenix.protocol.injector.player.PlayerInjectorBuilder;
+import com.comphenix.protocol.injector.player.PlayerInjectionHandler.ConflictStrategy;
 import com.comphenix.protocol.injector.spigot.SpigotPacketInjector;
 import com.comphenix.protocol.reflect.FieldAccessException;
 import com.comphenix.protocol.reflect.FuzzyReflection;
@@ -620,7 +621,7 @@ public final class PacketFilterManager implements ProtocolManager, ListenerInvok
 	 */
 	public void initializePlayers(Player[] players) {
 		for (Player player : players)
-			playerInjection.injectPlayer(player);
+			playerInjection.injectPlayer(player, ConflictStrategy.OVERRIDE);
 	}
 	
 	/**
@@ -680,7 +681,7 @@ public final class PacketFilterManager implements ProtocolManager, ListenerInvok
     private void onPlayerJoin(PlayerJoinEvent event) {
 		try {
 			// This call will be ignored if no listeners are registered
-			playerInjection.injectPlayer(event.getPlayer());
+			playerInjection.injectPlayer(event.getPlayer(), ConflictStrategy.OVERRIDE);
 		} catch (Exception e) {
 			reporter.reportDetailed(PacketFilterManager.this, "Unable to inject player.", e, event);
 		}

ProtocolLib/src/main/java/com/comphenix/protocol/injector/player/NetLoginInjector.java

@@ -24,6 +24,7 @@ import org.bukkit.entity.Player;
 
 import com.comphenix.protocol.error.ErrorReporter;
 import com.comphenix.protocol.injector.GamePhase;
+import com.comphenix.protocol.injector.player.PlayerInjectionHandler.ConflictStrategy;
 import com.comphenix.protocol.injector.server.TemporaryPlayerFactory;
 import com.comphenix.protocol.utility.MinecraftReflection;
 import com.google.common.collect.Maps;
@@ -64,7 +65,9 @@ class NetLoginInjector {
 				return inserting;
 			
 			Player temporary = playerFactory.createTemporaryPlayer(server);
-			PlayerInjector injector = injectionHandler.injectPlayer(temporary, inserting, GamePhase.LOGIN);
+			// Note that we bail out if there's an existing player injector
+			PlayerInjector injector = injectionHandler.injectPlayer(
+					temporary, inserting, ConflictStrategy.BAIL_OUT, GamePhase.LOGIN);
 			
 			if (injector != null) {
 				// Update injector as well

ProtocolLib/src/main/java/com/comphenix/protocol/injector/player/PlayerInjectionHandler.java

@@ -12,6 +12,23 @@ import com.comphenix.protocol.injector.GamePhase;
 import com.comphenix.protocol.injector.PacketFilterManager.PlayerInjectHooks;
 
 public interface PlayerInjectionHandler {
+	/**
+	 * How to handle a previously existing player injection.
+	 * 
+	 * @author Kristian
+	 */
+	public enum ConflictStrategy {
+		/**
+		 * Override it.
+		 */
+		OVERRIDE,
+		
+		/**
+		 * Immediately exit.
+		 */
+		BAIL_OUT;
+	}
+	
 	/**
 	 * Retrieves how the server packets are read.
 	 * @return Injection method for reading server packets.
@@ -64,8 +81,9 @@ public interface PlayerInjectionHandler {
 	 * <p>
 	 * This call will  be ignored if there's no listener that can receive the given events.
 	 * @param player - player to hook.
+	 * @param strategy - how to handle injection conflicts.
 	 */
-	public abstract void injectPlayer(Player player);
+	public abstract void injectPlayer(Player player, ConflictStrategy strategy);
 
 	/**
 	 * Invoke special routines for handling disconnect before a player is uninjected.

ProtocolLib/src/main/java/com/comphenix/protocol/injector/player/ProxyPlayerInjectionHandler.java

@@ -253,12 +253,13 @@ class ProxyPlayerInjectionHandler implements PlayerInjectionHandler {
 	 * <p>
 	 * This call will  be ignored if there's no listener that can receive the given events.
 	 * @param player - player to hook.
+	 * @param strategy - how to handle previous player injections.
 	 */
 	@Override
-	public void injectPlayer(Player player) {
+	public void injectPlayer(Player player, ConflictStrategy strategy) {
 		// Inject using the player instance itself
 		if (isInjectionNecessary(GamePhase.PLAYING)) {
-			injectPlayer(player, player, GamePhase.PLAYING);
+			injectPlayer(player, player, strategy, GamePhase.PLAYING);
 		}
 	}
 	
@@ -281,7 +282,7 @@ class ProxyPlayerInjectionHandler implements PlayerInjectionHandler {
 	 * @param phase - the current game phase.
 	 * @return The resulting player injector, or NULL if the injection failed.
 	 */
-	PlayerInjector injectPlayer(Player player, Object injectionPoint, GamePhase phase) {
+	PlayerInjector injectPlayer(Player player, Object injectionPoint, ConflictStrategy stategy, GamePhase phase) {
 		if (player == null)
 			throw new IllegalArgumentException("Player cannot be NULL.");
 		if (injectionPoint == null)
@@ -291,12 +292,12 @@ class ProxyPlayerInjectionHandler implements PlayerInjectionHandler {
 		
 		// Unfortunately, due to NetLoginHandler, multiple threads may potentially call this method.
 		synchronized (player) {
-			return injectPlayerInternal(player, injectionPoint, phase);
+			return injectPlayerInternal(player, injectionPoint, stategy, phase);
 		}
 	}
 	
 	// Unsafe variant of the above
-	private PlayerInjector injectPlayerInternal(Player player, Object injectionPoint, GamePhase phase) {
+	private PlayerInjector injectPlayerInternal(Player player, Object injectionPoint, ConflictStrategy stategy, GamePhase phase) {
 		PlayerInjector injector = playerInjection.get(player);
 		PlayerInjectHooks tempHook = getPlayerHook(phase);
 		PlayerInjectHooks permanentHook = tempHook;
@@ -328,9 +329,14 @@ class ProxyPlayerInjectionHandler implements PlayerInjectionHandler {
 
 						// Close any previously associated hooks before we proceed
 						if (previous != null && !(player instanceof Factory)) {
-							uninjectPlayer(previous.getPlayer(), true);
+							switch (stategy) {
+							case OVERRIDE:
+								uninjectPlayer(previous.getPlayer(), true);
+								break;
+							case BAIL_OUT:
+								return null;
+							}
 						}
-						
 						injector.injectManager();
 						
 						// Save injector

ProtocolLib/src/main/java/com/comphenix/protocol/injector/spigot/DummyPlayerHandler.java

@@ -79,7 +79,8 @@ class DummyPlayerHandler implements PlayerInjectionHandler {
 	}
 	
 	@Override
-	public void injectPlayer(Player player) {
+	public void injectPlayer(Player player, ConflictStrategy strategy) {
+		// We don't care about strategy
 		injector.injectPlayer(player);
 	}