Added an unknown command callback

src/main/java/net/minestom/server/command/CommandManager.java

@@ -20,6 +20,7 @@ import net.minestom.server.entity.Player;
 import net.minestom.server.event.player.PlayerCommandEvent;
 import net.minestom.server.network.packet.server.play.DeclareCommandsPacket;
 import net.minestom.server.utils.ArrayUtils;
+import net.minestom.server.utils.callback.CommandCallback;
 import net.minestom.server.utils.validate.Check;
 import org.apache.commons.lang3.tuple.Pair;
 import org.jetbrains.annotations.NotNull;
@@ -44,6 +45,8 @@ public final class CommandManager {
     private final CommandDispatcher dispatcher = new CommandDispatcher();
     private final Map<String, CommandProcessor> commandProcessorMap = new HashMap<>();
 
+    private CommandCallback unknownCommandCallback;
+
     public CommandManager() {
         running = true;
         // Setup console thread
@@ -153,8 +156,12 @@ public final class CommandManager {
             final String[] splitCommand = command.split(" ");
             final String commandName = splitCommand[0];
             final CommandProcessor commandProcessor = commandProcessorMap.get(commandName.toLowerCase());
-            if (commandProcessor == null)
+            if (commandProcessor == null) {
+                if (unknownCommandCallback != null) {
+                    this.unknownCommandCallback.apply(sender, command);
+                }
                 return false;
+            }
 
             // Execute the legacy-command
             final String[] args = command.substring(command.indexOf(" ") + 1).split(" ");
@@ -164,6 +171,26 @@ public final class CommandManager {
         }
     }
 
+    /**
+     * Gets the callback executed once an unknown command is run.
+     *
+     * @return the unknown command callback, null if not any
+     */
+    @Nullable
+    public CommandCallback getUnknownCommandCallback() {
+        return unknownCommandCallback;
+    }
+
+    /**
+     * Sets the callback executed once an unknown command is run.
+     *
+     * @param unknownCommandCallback the new unknown command callback,
+     *                               setting it to null mean that nothing will be executed
+     */
+    public void setUnknownCommandCallback(@Nullable CommandCallback unknownCommandCallback) {
+        this.unknownCommandCallback = unknownCommandCallback;
+    }
+
     /**
      * Gets the {@link ConsoleSender} (which is used as a {@link CommandSender}).
      *

src/main/java/net/minestom/server/utils/callback/CommandCallback.java

@@ -0,0 +1,22 @@
+package net.minestom.server.utils.callback;
+
+import net.minestom.server.command.CommandSender;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Functional interface used by the {@link net.minestom.server.command.CommandManager}
+ * to execute a callback if an unknown command is run.
+ * You can set it with {@link net.minestom.server.command.CommandManager#setUnknownCommandCallback(CommandCallback)}.
+ */
+@FunctionalInterface
+public interface CommandCallback {
+
+    /**
+     * Executed if an unknown command is run.
+     *
+     * @param sender  the command sender
+     * @param command the complete command string
+     */
+    void apply(@NotNull CommandSender sender, @NotNull String command);
+
+}

src/test/java/demo/Main.java

@@ -36,6 +36,8 @@ public class Main {
         commandManager.register(new ShutdownCommand());
         commandManager.register(new TeleportCommand());
 
+        commandManager.setUnknownCommandCallback((sender, command) -> sender.sendMessage("unknown command"));
+
 
         StorageManager storageManager = MinecraftServer.getStorageManager();
         storageManager.defineDefaultStorageSystem(FileStorageSystem::new);