introduce no-op callback concept to simplify implementations

api/src/main/java/net/kyori/adventure/audience/Audience.java

@@ -739,8 +739,10 @@ default void setResourcePacks(final @NotNull ResourcePackRequestLike request, fi
    * @see ResourcePackRequest
    * @since 4.15.0
    */
+  @ForwardingAudienceOverrideNotRequired
   @SuppressWarnings("checkstyle:MethodName")
   default void setResourcePacks(final @NotNull ResourcePackRequest request, final @NotNull ResourcePackRequest@NotNull... others) {
+    this.setResourcePacks(ResourcePackCallback.noOp(), request, others);
   }
 
   /**
@@ -808,7 +810,9 @@ default void sendResourcePacks(final @NotNull ResourcePackRequestLike request, f
    * @see ResourcePackRequest
    * @since 4.15.0
    */
+  @ForwardingAudienceOverrideNotRequired
   default void sendResourcePacks(final @NotNull ResourcePackRequest request, final @NotNull ResourcePackRequest@NotNull... others) {
+    this.sendResourcePacks(ResourcePackCallback.noOp(), request, others);
   }
 
   /**

api/src/main/java/net/kyori/adventure/audience/Audiences.java

@@ -28,6 +28,7 @@
 import java.util.function.Consumer;
 import java.util.stream.Collector;
 import java.util.stream.Collectors;
+import net.kyori.adventure.resource.ResourcePackCallback;
 import net.kyori.adventure.text.ComponentLike;
 import org.jetbrains.annotations.NotNull;
 
@@ -55,4 +56,12 @@ private Audiences() {
   public static @NotNull Consumer<? super Audience> sendingMessage(final @NotNull ComponentLike message) {
     return audience -> audience.sendMessage(message);
   }
+
+  static @NotNull ResourcePackCallback unwrapCallback(final Audience forwarding, final Audience dest, final @NotNull ResourcePackCallback cb) {
+    if (cb == ResourcePackCallback.noOp()) return cb;
+
+    return (uuid, status, audience) -> {
+      cb.packEventReceived(uuid, status, audience == dest ? forwarding : audience);
+    };
+  }
 }

api/src/main/java/net/kyori/adventure/audience/ForwardingAudience.java

@@ -202,21 +202,11 @@ default void openBook(final @NotNull Book book) {
     for (final Audience audience : this.audiences()) audience.openBook(book);
   }
 
-  @Override
-  default void setResourcePacks(final @NotNull ResourcePackRequest request, final @NotNull ResourcePackRequest@NotNull... others) {
-    for (final Audience audience : this.audiences()) audience.setResourcePacks(request, others);
-  }
-
   @Override
   default void setResourcePacks(final @NotNull ResourcePackCallback cb, final @NotNull ResourcePackRequest request, final @NotNull ResourcePackRequest @NotNull ... others) {
     for (final Audience audience : this.audiences()) audience.setResourcePacks(cb, request, others);
   }
 
-  @Override
-  default void sendResourcePacks(final @NotNull ResourcePackRequest request, final @NotNull ResourcePackRequest@NotNull... others) {
-    for (final Audience audience : this.audiences()) audience.sendResourcePacks(request, others);
-  }
-
   @Override
   default void sendResourcePacks(final @NotNull ResourcePackCallback cb, final @NotNull ResourcePackRequest request, final @NotNull ResourcePackRequest@NotNull ... others) {
     for (final Audience audience : this.audiences()) audience.sendResourcePacks(cb, request, others);
@@ -395,24 +385,14 @@ default void openBook(final @NotNull Book book) {
       this.audience().openBook(book);
     }
 
-    @Override
-    default void setResourcePacks(final @NotNull ResourcePackRequest request, final @NotNull ResourcePackRequest... others) {
-      this.audience().setResourcePacks(request, others);
-    }
-
     @Override
     default void setResourcePacks(final @NotNull ResourcePackCallback cb, final @NotNull ResourcePackRequest request, final @NotNull ResourcePackRequest @NotNull ... others) {
-      this.audience().setResourcePacks((uuid, status, audience) -> cb.packEventReceived(uuid, status, this), request, others);
-    }
-
-    @Override
-    default void sendResourcePacks(final @NotNull ResourcePackRequest request, final @NotNull ResourcePackRequest@NotNull... others) {
-      this.audience().sendResourcePacks(request, others);
+      this.audience().setResourcePacks(Audiences.unwrapCallback(this, this.audience(), cb), request, others);
     }
 
     @Override
     default void sendResourcePacks(final @NotNull ResourcePackCallback cb, final @NotNull ResourcePackRequest request, final @NotNull ResourcePackRequest @NotNull ... others) {
-      this.audience().sendResourcePacks((uuid, status, audience) -> cb.packEventReceived(uuid, status, this), request, others);
+      this.audience().sendResourcePacks(Audiences.unwrapCallback(this, this.audience(), cb), request, others);
     }
 
     @Override

api/src/main/java/net/kyori/adventure/resource/ResourcePackCallback.java

@@ -35,6 +35,18 @@
  */
 @FunctionalInterface
 public interface ResourcePackCallback {
+  /**
+   * Create a pack callback that performs no operation.
+   *
+   * <p>Multiple calls to this method are guaranteed to return callback functions with equal identity.</p>
+   *
+   * @return the no-op callback
+   * @since 4.15.0
+   */
+  static @NotNull ResourcePackCallback noOp() {
+    return ResourcePackCallbacks.NO_OP;
+  }
+
   /**
    * Create a pack callback that will only execute the provided functions when the pack application has completed, discarding all intermediate events.
    *

api/src/main/java/net/kyori/adventure/resource/ResourcePackCallbacks.java

@@ -0,0 +1,31 @@
+/*
+ * This file is part of adventure, licensed under the MIT License.
+ *
+ * Copyright (c) 2017-2023 KyoriPowered
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package net.kyori.adventure.resource;
+
+final class ResourcePackCallbacks {
+  private ResourcePackCallbacks() {
+  }
+
+  static final ResourcePackCallback NO_OP = (uuid, status, audience) -> {};
+}