Allow listening to plugin messages during configuration phase (#12775)

paper-api/src/main/java/org/bukkit/plugin/messaging/Messenger.java

@@ -1,9 +1,11 @@
 package org.bukkit.plugin.messaging;
 
 import java.util.Set;
+import io.papermc.paper.connection.PlayerConnection;
 import org.bukkit.NamespacedKey;
 import org.bukkit.entity.Player;
 import org.bukkit.plugin.Plugin;
+import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
 
 /**
@@ -230,4 +232,14 @@ public interface Messenger {
      * @param message Raw payload of the message.
      */
     public void dispatchIncomingMessage(@NotNull Player source, @NotNull String channel, byte @NotNull [] message);
+
+    /**
+     * Dispatches the specified incoming message to any registered listeners.
+     *
+     * @param source Source of the message.
+     * @param channel Channel that the message was sent by.
+     * @param message Raw payload of the message.
+     */
+    @ApiStatus.Experimental
+    public void dispatchIncomingMessage(@NotNull PlayerConnection source, @NotNull String channel, byte @NotNull [] message);
 }

paper-api/src/main/java/org/bukkit/plugin/messaging/PluginMessageListener.java

@@ -1,7 +1,9 @@
 package org.bukkit.plugin.messaging;
 
 import io.papermc.paper.connection.PlayerCommonConnection;
+import io.papermc.paper.connection.PlayerConnection;
 import org.bukkit.entity.Player;
+import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
 
 /**
@@ -28,7 +30,8 @@ public interface PluginMessageListener {
      * @param connection Source of the message.
      * @param message The raw message that was sent.
      */
-    default void onPluginMessageReceived(@NotNull String channel, @NotNull PlayerCommonConnection connection, byte @NotNull [] message) {
+    @ApiStatus.Experimental
+    default void onPluginMessageReceived(@NotNull String channel, @NotNull PlayerConnection connection, byte @NotNull [] message) {
 
     }
 }

paper-api/src/main/java/org/bukkit/plugin/messaging/StandardMessenger.java

@@ -8,6 +8,7 @@ import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import java.util.logging.Level;
+import io.papermc.paper.connection.PlayerConnection;
 import org.bukkit.entity.Player;
 import org.bukkit.plugin.Plugin;
 import org.jetbrains.annotations.NotNull;
@@ -462,6 +463,30 @@ public class StandardMessenger implements Messenger {
         }
     }
 
+    @Override
+    public void dispatchIncomingMessage(@NotNull PlayerConnection source, @NotNull String channel, byte @NotNull [] message) {
+        if (source == null) {
+            throw new IllegalArgumentException("Player source cannot be null");
+        }
+        if (message == null) {
+            throw new IllegalArgumentException("Message cannot be null");
+        }
+        channel = validateAndCorrectChannel(channel);
+
+        Set<PluginMessageListenerRegistration> registrations = getIncomingChannelRegistrations(channel);
+
+        for (PluginMessageListenerRegistration registration : registrations) {
+            try {
+                registration.getListener().onPluginMessageReceived(channel, source, message);
+            } catch (Throwable t) {
+                registration.getPlugin().getLogger().log(Level.WARNING,
+                    String.format("Plugin %s generated an exception whilst handling plugin message",
+                        registration.getPlugin().getDescription().getFullName()
+                    ), t);
+            }
+        }
+    }
+
     /**
      * Validates a Plugin Channel name.
      *