fix: obj loader not rendering parts with the same name [1.21.4]

src/main/java/net/neoforged/neoforge/client/model/obj/ObjModel.java

@@ -6,7 +6,8 @@
 package net.neoforged.neoforge.client.model.obj;
 
 import com.google.common.collect.Lists;
-import com.google.common.collect.Maps;
+import com.google.common.collect.Multimap;
+import com.google.common.collect.MultimapBuilder;
 import com.mojang.math.Transformation;
 import java.io.IOException;
 import java.util.Arrays;
@@ -55,7 +56,7 @@ public class ObjModel extends AbstractUnbakedModel {
             new Vec2(1, 0),
     };
 
-    private final Map<String, ModelGroup> parts = Maps.newLinkedHashMap();
+    private final Multimap<String, ModelGroup> parts = MultimapBuilder.linkedHashKeys().arrayListValues().build();
 
     private final List<Vector3f> positions = Lists.newArrayList();
     private final List<Vec2> texCoords = Lists.newArrayList();
@@ -441,7 +442,7 @@ protected void addNamesRecursively(Set<String> names) {
     }
 
     public class ModelGroup extends ModelObject {
-        final Map<String, ModelObject> parts = Maps.newLinkedHashMap();
+        final Multimap<String, ModelObject> parts = MultimapBuilder.linkedHashKeys().arrayListValues().build();
 
         ModelGroup(String name) {
             super(name);

tests/src/generated/resources/assets/new_model_loader_test/blockstates/obj_block_same_part_names.json

@@ -0,0 +1,19 @@
+{
+  "variants": {
+    "facing=east": {
+      "model": "new_model_loader_test:block/obj_block_same_part_names",
+      "y": 90
+    },
+    "facing=north": {
+      "model": "new_model_loader_test:block/obj_block_same_part_names"
+    },
+    "facing=south": {
+      "model": "new_model_loader_test:block/obj_block_same_part_names",
+      "y": 180
+    },
+    "facing=west": {
+      "model": "new_model_loader_test:block/obj_block_same_part_names",
+      "y": 270
+    }
+  }
+}

tests/src/generated/resources/assets/new_model_loader_test/models/block/obj_block_same_part_names.json

@@ -0,0 +1,9 @@
+{
+  "flip_v": true,
+  "loader": "neoforge:obj",
+  "model": "new_model_loader_test:models/item/sugar_glider_same_part_names.obj",
+  "textures": {
+    "particle": "#qr",
+    "qr": "minecraft:block/oak_planks"
+  }
+}

tests/src/main/java/net/neoforged/neoforge/oldtest/client/model/NewModelLoaderTest.java

@@ -68,24 +68,11 @@ public class NewModelLoaderTest {
     public static final DeferredRegister.Blocks BLOCKS = DeferredRegister.createBlocks(MODID);
     public static final DeferredRegister.Items ITEMS = DeferredRegister.createItems(MODID);
 
-    public static DeferredBlock<Block> obj_block = BLOCKS.registerBlock("obj_block", props -> new Block(props) {
-        @Override
-        protected void createBlockStateDefinition(StateDefinition.Builder<Block, BlockState> builder) {
-            builder.add(BlockStateProperties.HORIZONTAL_FACING);
-        }
+    public static DeferredBlock<Block> obj_block = BLOCKS.registerBlock("obj_block", TestBlock::new, Block.Properties.of().mapColor(MapColor.WOOD).strength(10));
 
-        @Nullable
-        @Override
-        public BlockState getStateForPlacement(BlockPlaceContext context) {
-            return defaultBlockState().setValue(
-                    BlockStateProperties.HORIZONTAL_FACING, context.getHorizontalDirection());
-        }
-
-        @Override
-        public VoxelShape getShape(BlockState state, BlockGetter worldIn, BlockPos pos, CollisionContext context) {
-            return Block.box(2, 2, 2, 14, 14, 14);
-        }
-    }, Block.Properties.of().mapColor(MapColor.WOOD).strength(10));
+    // Same at obj_block except all the parts in the obj model have the same name,
+    // this is a test for neoforged/NeoForge#1755 that was fixed by neoforged/NeoForge#1759
+    public static DeferredBlock<Block> obj_block_same_part_names = BLOCKS.registerBlock("obj_block_same_part_names", TestBlock::new, Block.Properties.of().mapColor(MapColor.WOOD).strength(10));
 
     public static DeferredItem<Item> obj_item = ITEMS.registerItem("obj_block", props -> new BlockItem(obj_block.get(), props.useBlockDescriptionPrefix()) {
         @Override
@@ -94,6 +81,8 @@ public boolean canEquip(ItemStack stack, EquipmentSlot armorType, LivingEntity e
         }
     });
 
+    public static DeferredItem<Item> obj_item_same_part_names = ITEMS.registerItem("obj_block_same_part_names", props -> new BlockItem(obj_block_same_part_names.get(), props));
+
     public static DeferredItem<Item> custom_transforms = ITEMS.registerSimpleItem("custom_transforms");
 
     public static DeferredItem<Item> custom_vanilla_loader = ITEMS.registerSimpleItem("custom_vanilla_loader");
@@ -117,6 +106,7 @@ private void addCreative(BuildCreativeModeTabContentsEvent event) {
         if (event.getTabKey() == CreativeModeTabs.INGREDIENTS) {
             Arrays.asList(
                     obj_item,
+                    obj_item_same_part_names,
                     custom_transforms,
                     custom_vanilla_loader,
                     custom_loader,
@@ -129,6 +119,29 @@ public void modelRegistry(ModelEvent.RegisterLoaders event) {
         event.register(ResourceLocation.fromNamespaceAndPath(MODID, "custom_loader"), new TestLoader());
     }
 
+    static class TestBlock extends Block {
+        public TestBlock(Properties properties) {
+            super(properties);
+        }
+
+        @Override
+        protected void createBlockStateDefinition(StateDefinition.Builder<Block, BlockState> builder) {
+            builder.add(BlockStateProperties.HORIZONTAL_FACING);
+        }
+
+        @Nullable
+        @Override
+        public BlockState getStateForPlacement(BlockPlaceContext context) {
+            return defaultBlockState().setValue(
+                    BlockStateProperties.HORIZONTAL_FACING, context.getHorizontalDirection());
+        }
+
+        @Override
+        public VoxelShape getShape(BlockState state, BlockGetter worldIn, BlockPos pos, CollisionContext context) {
+            return Block.box(2, 2, 2, 14, 14, 14);
+        }
+    }
+
     static class TestLoader implements UnbakedModelLoader<TestModel> {
         @Override
         public TestModel read(JsonObject jsonObject, JsonDeserializationContext jsonDeserializationContext) throws JsonParseException {
@@ -203,15 +216,20 @@ public BlockStates(PackOutput output, ExistingFileHelper exFileHelper) {
 
         @Override
         protected void registerStatesAndModels() {
+            createModelAndBlockState(obj_block, "sugar_glider");
+            createModelAndBlockState(obj_block_same_part_names, "sugar_glider_same_part_names");
+        }
+
+        private void createModelAndBlockState(DeferredBlock<Block> block, String objModel) {
             BlockModelBuilder model = models()
-                    .getBuilder(NewModelLoaderTest.obj_block.getId().getPath())
+                    .getBuilder(block.getId().getPath())
                     .customLoader(ObjModelBuilder::begin)
-                    .modelLocation(ResourceLocation.fromNamespaceAndPath("new_model_loader_test", "models/item/sugar_glider.obj"))
+                    .modelLocation(ResourceLocation.fromNamespaceAndPath("new_model_loader_test", "models/item/" + objModel + ".obj"))
                     .flipV(true)
                     .end()
                     .texture("qr", "minecraft:block/oak_planks")
                     .texture("particle", "#qr");
-            getVariantBuilder(NewModelLoaderTest.obj_block.get())
+            getVariantBuilder(block.get())
                     .partialState()
                     .with(BlockStateProperties.HORIZONTAL_FACING, Direction.EAST)
                     .addModels(new ConfiguredModel(model, 0, 90, false))