Add keyStream() API to registries (#12479)

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

@@ -525,6 +525,13 @@ public interface Registry<T extends Keyed> extends Iterable<T> {
      */
     Stream<T> stream();
 
+    /**
+     * Returns a new stream, which contains all registry keys, which are registered to the registry.
+     *
+     * @return a stream of all registry keys
+     */
+    Stream<NamespacedKey> keyStream();
+
     /**
      * Attempts to match the registered object with the given key.
      * <p>
@@ -591,6 +598,11 @@ public interface Registry<T extends Keyed> extends Iterable<T> {
             return this.map.values().iterator();
         }
 
+        @Override
+        public Stream<NamespacedKey> keyStream() {
+            return this.map.keySet().stream();
+        }
+
         @ApiStatus.Internal
         @Deprecated(since = "1.20.6", forRemoval = true)
         public Class<T> getType() {
@@ -606,6 +618,11 @@ public interface Registry<T extends Keyed> extends Iterable<T> {
             return StreamSupport.stream(this.spliterator(), false);
         }
 
+        @Override
+        public Stream<NamespacedKey> keyStream() {
+            return stream().map(this::getKey);
+        }
+
         @Override
         public int size() {
             return Iterables.size(this);

paper-server/src/main/java/io/papermc/paper/registry/legacy/DelayedRegistry.java

@@ -49,6 +49,11 @@ public final class DelayedRegistry<T extends Keyed, R extends Registry<T>> imple
         return this.delegate().stream();
     }
 
+    @Override
+    public Stream<NamespacedKey> keyStream() {
+        return this.delegate().keyStream();
+    }
+
     @Override
     public int size() {
         return this.delegate().size();

paper-server/src/main/java/org/bukkit/craftbukkit/CraftRegistry.java

@@ -233,6 +233,12 @@ public class CraftRegistry<B extends Keyed, M> implements Registry<B> {
         return this.minecraftRegistry.keySet().stream().map(minecraftKey -> this.get(CraftNamespacedKey.fromMinecraft(minecraftKey)));
     }
 
+    @NotNull
+    @Override
+    public Stream<NamespacedKey> keyStream() {
+        return this.minecraftRegistry.keySet().stream().map(CraftNamespacedKey::fromMinecraft);
+    }
+
     @Override
     public int size() {
         return this.minecraftRegistry.size();