Fix command packet (#900)

fix https://github.com/PaperMC/Velocity/issues/898

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/chat/LastSeenMessages.java

@@ -44,4 +44,8 @@ public class LastSeenMessages {
     ProtocolUtils.writeVarInt(buf, offset);
     buf.writeBytes(Arrays.copyOf(acknowledged.toByteArray(), DIV_FLOOR));
   }
+
+  public boolean isEmpty() {
+    return acknowledged.isEmpty();
+  }
 }

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/chat/legacy/LegacyCommandHandler.java

@@ -43,7 +43,7 @@ public class LegacyCommandHandler implements CommandHandler<LegacyChat> {
     String command = packet.getMessage().substring(1);
     queueCommandResult(this.server, this.player, event -> {
       CommandExecuteEvent.CommandResult result = event.getResult();
-      if (!result.isAllowed()) {
+      if (result == CommandExecuteEvent.CommandResult.denied()) {
         return CompletableFuture.completedFuture(null);
       }
       String commandToRun = result.getCommand().orElse(command);

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/chat/session/SessionCommandHandler.java

@@ -42,8 +42,8 @@ public class SessionCommandHandler implements CommandHandler<SessionPlayerComman
   public void handlePlayerCommandInternal(SessionPlayerCommand packet) {
     queueCommandResult(this.server, this.player, event -> {
       CommandExecuteEvent.CommandResult result = event.getResult();
-      if (!result.isAllowed()) {
-        if (!packet.argumentSignatures.isEmpty()) {
+      if (result == CommandExecuteEvent.CommandResult.denied()) {
+        if (packet.isSigned()) {
           logger.fatal("A plugin tried to deny a command with signable component(s). " + "This is not supported. "
               + "Disconnecting player " + player.getUsername());
           player.disconnect(Component.text(
@@ -54,10 +54,10 @@ public class SessionCommandHandler implements CommandHandler<SessionPlayerComman
 
       String commandToRun = result.getCommand().orElse(packet.command);
       if (result.isForwardToServer()) {
-        if (!packet.argumentSignatures.isEmpty() && commandToRun.equals(packet.command)) {
+        if (!packet.isSigned() && commandToRun.equals(packet.command)) {
           return CompletableFuture.completedFuture(packet);
         } else {
-          if (!packet.argumentSignatures.isEmpty()) {
+          if (packet.isSigned()) {
             logger.fatal("A plugin tried to change a command with signed component(s). " + "This is not supported. "
                 + "Disconnecting player " + player.getUsername());
             player.disconnect(Component.text(
@@ -76,10 +76,10 @@ public class SessionCommandHandler implements CommandHandler<SessionPlayerComman
 
       return runCommand(this.server, this.player, commandToRun, hasRun -> {
         if (!hasRun) {
-          if (!packet.argumentSignatures.isEmpty() && commandToRun.equals(packet.command)) {
+          if (packet.isSigned() && commandToRun.equals(packet.command)) {
             return packet;
           } else {
-            if (!packet.argumentSignatures.isEmpty()) {
+            if (packet.isSigned()) {
               logger.fatal("A plugin tried to change a command with signed component(s). " + "This is not supported. "
                   + "Disconnecting player " + player.getUsername());
               player.disconnect(Component.text(

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/chat/session/SessionPlayerCommand.java

@@ -61,6 +61,10 @@ public class SessionPlayerCommand implements MinecraftPacket {
     return timeStamp;
   }
 
+  public boolean isSigned() {
+    return salt != 0 || !lastSeenMessages.isEmpty() || !argumentSignatures.isEmpty();
+  }
+
   @Override
   public boolean handle(MinecraftSessionHandler handler) {
     return handler.handle(this);