Ensure custom blocks can be represented at any index

core/src/main/java/org/geysermc/geyser/item/Items.java

@@ -30,8 +30,6 @@ import org.geysermc.geyser.item.type.*;
 import org.geysermc.geyser.level.block.Blocks;
 import org.geysermc.geyser.registry.Registries;
 
-import java.util.Collections;
-
 import static org.geysermc.geyser.item.type.Item.builder;
 
 /**
@@ -1378,11 +1376,7 @@ public final class Items {
 
     public static <T extends Item> T register(T item, int id) {
         item.setJavaId(id);
-        // This makes sure that the array is large enough to put the java item at the correct location
-        if (Registries.JAVA_ITEMS.get().size() <= id) {
-            Registries.JAVA_ITEMS.get().addAll(Collections.nCopies(id - Registries.JAVA_ITEMS.get().size() + 1, AIR));
-        }
-        Registries.JAVA_ITEMS.get().set(id, item);
+        Registries.JAVA_ITEMS.registerWithAnyIndex(id, item, AIR);
         Registries.JAVA_ITEM_IDENTIFIERS.register(item.javaIdentifier(), item);
         return item;
     }

core/src/main/java/org/geysermc/geyser/registry/ListRegistry.java

@@ -29,6 +29,7 @@ import org.checkerframework.checker.nullness.qual.Nullable;
 import org.geysermc.geyser.registry.loader.RegistryLoader;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.function.Supplier;
 
@@ -94,6 +95,25 @@ public class ListRegistry<M> extends Registry<List<M>> {
         return this.mappings.set(index, value);
     }
 
+    /**
+     * Registers a new value into this registry with the given index, even if this value would normally be outside
+     * the range of a list.
+     *
+     * @param index the index
+     * @param value the value
+     * @param defaultValue the default value to fill empty spaces in the registry with.
+     * @return a new value into this registry with the given index.
+     */
+    public M registerWithAnyIndex(int index, M value, M defaultValue) {
+        if (this.frozen) {
+            throw new IllegalStateException("Registry should not be modified after frozen!");
+        }
+        if (this.mappings.size() <= index) {
+            this.mappings.addAll(Collections.nCopies(index - this.mappings.size() + 1, defaultValue));
+        }
+        return this.mappings.set(index, value);
+    }
+
     /**
      * Mark this registry as unsuitable for new additions. The backing list will then be optimized for storage.
      */

core/src/main/java/org/geysermc/geyser/registry/Registries.java

@@ -127,7 +127,10 @@ public final class Registries {
      */
     public static final PacketTranslatorRegistry<Packet> JAVA_PACKET_TRANSLATORS = PacketTranslatorRegistry.create();
 
-    public static final SimpleRegistry<List<Item>> JAVA_ITEMS = SimpleRegistry.create(RegistryLoaders.empty(ArrayList::new));
+    /**
+     * A registry containing all Java items ordered by their network ID.
+     */
+    public static final ListRegistry<Item> JAVA_ITEMS = ListRegistry.create(RegistryLoaders.empty(ArrayList::new));
 
     public static final SimpleMappedRegistry<String, Item> JAVA_ITEM_IDENTIFIERS = SimpleMappedRegistry.create(RegistryLoaders.empty(Object2ObjectOpenHashMap::new));
 

core/src/main/java/org/geysermc/geyser/registry/populator/BlockRegistryPopulator.java

@@ -213,7 +213,6 @@ public final class BlockRegistryPopulator {
             GeyserBedrockBlock[] javaToBedrockBlocks = new GeyserBedrockBlock[JAVA_BLOCKS_SIZE];
             GeyserBedrockBlock[] javaToVanillaBedrockBlocks = new GeyserBedrockBlock[JAVA_BLOCKS_SIZE];
 
-            //List<String> javaToBedrockIdentifiers = new ArrayList<>(BlockRegistries.JAVA_BLOCKS.get().size());
             var javaToBedrockIdentifiers = new Int2ObjectOpenHashMap<String>();
             Block lastBlockSeen = null;
 
@@ -456,7 +455,7 @@ public final class BlockRegistryPopulator {
                 };
                 block.setJavaId(javaBlockState.stateGroupId());
 
-                BlockRegistries.JAVA_BLOCKS.get().add(javaBlockState.stateGroupId(), block); //TODO don't allow duplicates, allow blanks
+                BlockRegistries.JAVA_BLOCKS.registerWithAnyIndex(javaBlockState.stateGroupId(), block, Blocks.AIR);
                 BlockRegistries.JAVA_IDENTIFIER_TO_ID.register(javaId, stateRuntimeId);
                 BlockRegistries.BLOCK_STATES.register(stateRuntimeId, new BlockState(block, stateRuntimeId));
             }