feat(plugin): make Plugin extend Namespaced (#12867)

Co-authored-by: Bjarne Koll <git@lynxplay.dev>
Co-authored-by: Jake Potrebic <jake.m.potrebic@gmail.com>

paper-api/src/main/java/io/papermc/paper/plugin/configuration/PluginMeta.java

@@ -1,6 +1,9 @@
 package io.papermc.paper.plugin.configuration;
 
 import java.util.List;
+import java.util.Locale;
+import net.kyori.adventure.key.KeyPattern;
+import net.kyori.adventure.key.Namespaced;
 import org.bukkit.permissions.Permission;
 import org.bukkit.permissions.PermissionDefault;
 import org.bukkit.plugin.PluginLoadOrder;
@@ -14,7 +17,7 @@ import org.jspecify.annotations.Nullable;
  */
 @NullMarked
 @ApiStatus.NonExtendable
-public interface PluginMeta {
+public interface PluginMeta extends Namespaced {
 
     /**
      * Provides the name of the plugin. This name uniquely identifies the plugin amongst all loaded plugins on the
@@ -180,4 +183,10 @@ public interface PluginMeta {
      */
     @Nullable String getAPIVersion();
 
+    @KeyPattern.Namespace
+    @SuppressWarnings("PatternValidation")
+    @Override
+    default String namespace() {
+        return this.getName().toLowerCase(Locale.ROOT);
+    }
 }

paper-api/src/main/java/org/bukkit/NamespacedKey.java

@@ -72,7 +72,7 @@ public final class NamespacedKey implements Key, com.destroystokyo.paper.Namespa
     public NamespacedKey(@NotNull Plugin plugin, @NotNull String key) {
         Preconditions.checkArgument(plugin != null, "Plugin cannot be null");
         Preconditions.checkArgument(key != null, "Key cannot be null");
-        this.namespace = plugin.getName().toLowerCase(Locale.ROOT);
+        this.namespace = plugin.namespace();
         this.key = key.toLowerCase(Locale.ROOT);
 
         // Check validity after normalization

paper-api/src/main/java/org/bukkit/plugin/Plugin.java

@@ -3,6 +3,7 @@ package org.bukkit.plugin;
 import java.io.File;
 import java.io.InputStream;
 import java.util.logging.Logger;
+import net.kyori.adventure.key.Namespaced;
 import org.bukkit.Server;
 import org.bukkit.command.TabExecutor;
 import org.bukkit.configuration.file.FileConfiguration;
@@ -16,7 +17,7 @@ import org.jetbrains.annotations.Nullable;
  * <p>
  * The use of {@link PluginBase} is recommended for actual Implementation
  */
-public interface Plugin extends TabExecutor, io.papermc.paper.plugin.lifecycle.event.LifecycleEventOwner { // Paper
+public interface Plugin extends TabExecutor, io.papermc.paper.plugin.lifecycle.event.LifecycleEventOwner, Namespaced { // Paper
     /**
      * Returns the folder that the plugin data files are located in. The
      * folder may not yet exist.

paper-api/src/main/java/org/bukkit/plugin/PluginBase.java

@@ -1,6 +1,7 @@
 package org.bukkit.plugin;
 
 import org.jetbrains.annotations.NotNull;
+import java.util.Locale;
 
 /**
  * Represents a base {@link Plugin}
@@ -33,4 +34,10 @@ public abstract class PluginBase implements Plugin {
     public final String getName() {
         return getPluginMeta().getName(); // Paper
     }
+
+    @Override
+    @NotNull
+    public String namespace() {
+        return this.getPluginMeta().namespace();
+    }
 }

paper-server/src/main/java/io/papermc/paper/command/brigadier/PaperCommands.java

@@ -91,7 +91,7 @@ public class PaperCommands implements Commands, PaperRegistrar<LifecycleEventOwn
 
     @Override
     public @Unmodifiable Set<String> registerWithFlags(final PluginMeta pluginMeta, final LiteralCommandNode<CommandSourceStack> node, final @Nullable String description, final Collection<String> aliases, final Set<CommandRegistrationFlag> flags) {
-        return registerWithFlagsInternal(pluginMeta, pluginMeta.getName().toLowerCase(Locale.ROOT), null, node, description, aliases, flags);
+        return this.registerWithFlagsInternal(pluginMeta, pluginMeta.namespace(), null, node, description, aliases, flags);
     }
 
     public @Unmodifiable Set<String> registerWithFlagsInternal(final @Nullable PluginMeta pluginMeta, final String namespace, final @Nullable String helpNamespaceOverride, final LiteralCommandNode<CommandSourceStack> node, final @Nullable String description, final Collection<String> aliases, final Set<CommandRegistrationFlag> flags) {