Move appendClientbound/Serverbound methods to Protocol interface

api/src/main/java/com/viaversion/viaversion/api/ViaAPI.java

@@ -66,7 +66,7 @@ public interface ViaAPI<T> {
      * @return API version incremented with meaningful API changes
      */
     default int apiVersion() {
-        return 25;
+        return 26;
     }
 
     /**

api/src/main/java/com/viaversion/viaversion/api/protocol/AbstractProtocol.java

@@ -146,6 +146,7 @@ public abstract class AbstractProtocol<CU extends ClientboundPacketType, CM exte
         }
     }
 
+    @Override
     public void appendClientbound(final CU type, final PacketHandler handler) {
         final PacketMapping mapping = clientboundMappings.mappedPacket(type.state(), type.getId());
         if (mapping != null) {
@@ -155,6 +156,7 @@ public abstract class AbstractProtocol<CU extends ClientboundPacketType, CM exte
         }
     }
 
+    @Override
     public void appendServerbound(final SU type, final PacketHandler handler) {
         final PacketMapping mapping = serverboundMappings.mappedPacket(type.state(), type.getId());
         if (mapping != null) {

api/src/main/java/com/viaversion/viaversion/api/protocol/Protocol.java

@@ -36,8 +36,8 @@ import com.viaversion.viaversion.api.protocol.remapper.PacketHandler;
 import com.viaversion.viaversion.api.protocol.remapper.PacketRemapper;
 import com.viaversion.viaversion.api.rewriter.EntityRewriter;
 import com.viaversion.viaversion.api.rewriter.ItemRewriter;
-import com.viaversion.viaversion.api.rewriter.Rewriter;
 import com.viaversion.viaversion.api.rewriter.TagRewriter;
+import com.viaversion.viaversion.api.type.Type;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
 /**
@@ -242,6 +242,28 @@ public interface Protocol<CU extends ClientboundPacketType, CM extends Clientbou
      */
     boolean hasRegisteredServerbound(State state, int unmappedPacketId);
 
+    /**
+     * Appends a clientbound packet type handler with another, as opposed to replacing it entirely.
+     * <p>
+     * Use {@link PacketWrapper#set(Type, int, Object)} to change individual parts, or call
+     * {@link PacketWrapper#resetReader()} to reset the reader index.
+     *
+     * @param type    clientbound packet type
+     * @param handler packet handler
+     */
+    void appendClientbound(CU type, PacketHandler handler);
+
+    /**
+     * Appends a serverbound packet type handler with another, as opposed to replacing it entirely.
+     * <p>
+     * Use {@link PacketWrapper#set(Type, int, Object)} to change individual parts, or call
+     * {@link PacketWrapper#resetReader()} to reset the reader index.
+     *
+     * @param type    serverbound packet type
+     * @param handler packet handler
+     */
+    void appendServerbound(SU type, PacketHandler handler);
+
     /**
      * Transform a packet using this protocol
      *
@@ -268,7 +290,8 @@ public interface Protocol<CU extends ClientboundPacketType, CM extends Clientbou
      * @return object if present, else null
      */
     @Deprecated
-    @Nullable <T> T get(Class<T> objectClass);
+    @Nullable
+    <T> T get(Class<T> objectClass);
 
     /**
      * Caches an object, retrievable by using {@link #get(Class)}.