Allow client commands to control whether they can be invoked without prefix. (#3847)

src/main/java/net/minecraftforge/client/ClientCommandHandler.java

@@ -59,7 +59,8 @@ public class ClientCommandHandler extends CommandHandler
     {
         message = message.trim();
 
-        if (message.startsWith("/"))
+        boolean usedSlash = message.startsWith("/");
+        if (usedSlash)
         {
             message = message.substring(1);
         }
@@ -72,7 +73,7 @@ public class ClientCommandHandler extends CommandHandler
 
         try
         {
-            if (icommand == null)
+            if (icommand == null || (!usedSlash && icommand instanceof IClientCommand && !((IClientCommand)icommand).allowUsageWithoutPrefix(sender, message)))
             {
                 return 0;
             }

src/main/java/net/minecraftforge/client/IClientCommand.java

@@ -0,0 +1,39 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.client;
+
+import net.minecraft.command.ICommand;
+import net.minecraft.command.ICommandSender;
+
+/**
+ * Client-side commands can implement this interface to allow additional control over when the command may be used.
+ */
+public interface IClientCommand extends ICommand
+{
+
+    /**
+     * Determine whether this command can be used without the "/" prefix. By default this is true.
+     * @param sender the command sender
+     * @param message the message, without potential prefix
+     * @return true to allow the usage of this command without the prefix
+     */
+    boolean allowUsageWithoutPrefix(ICommandSender sender, String message);
+
+}