Warn unsigned messages

src/main/java/cc/reconnected/server/RccServer.java

@@ -85,6 +85,7 @@ public class RccServer implements ModInitializer {
     }
 
     public static final RegistryKey<MessageType> CHAT_TYPE = RegistryKey.of(RegistryKeys.MESSAGE_TYPE, new Identifier(MOD_ID, "chat"));
+    private static boolean warnedAboutUnsignedMessages = false;
 
     @Override
     public void onInitialize() {
@@ -196,4 +197,20 @@ public class RccServer implements ModInitializer {
         }
     }
 
+    public static void warnUnsignedMessages() {
+        if (warnedAboutUnsignedMessages)
+            return;
+        warnedAboutUnsignedMessages = true;
+
+        LOGGER.warn(
+                """
+                        !!! --- WARNING --- !!!
+                        Cannot retrieve message sender UUID!
+                        
+                        If you are using FabricProxy-Lite, consider disabling
+                        the `hackMessageChain` configuration!
+                        """
+        );
+    }
+
 }

src/main/java/cc/reconnected/server/mixin/SentMessageMixin.java

@@ -1,5 +1,6 @@
 package cc.reconnected.server.mixin;
 
+import cc.reconnected.server.RccServer;
 import cc.reconnected.server.core.customChat.CustomSentMessage;
 import net.minecraft.network.message.SentMessage;
 import net.minecraft.network.message.SignedMessage;
@@ -10,11 +11,11 @@ import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
 
 @Mixin(SentMessage.class)
 public interface SentMessageMixin {
-
     @Inject(method = "of", at = @At("HEAD"), cancellable = true)
     private static void rccServer$of(SignedMessage message, CallbackInfoReturnable<SentMessage> cir) {
 
-        if(message.isSenderMissing()) {
+        if (message.isSenderMissing()) {
+            RccServer.warnUnsignedMessages();
             cir.setReturnValue(new SentMessage.Profileless(message.getContent()));
         } else {
             cir.setReturnValue(new CustomSentMessage(message));