Query crafting remainders prior to shrinkage to fix bug caused by querying the empty stack's remainder (#3179)

Author: ApexModder

patches/net/minecraft/world/level/block/entity/AbstractFurnaceBlockEntity.java.patch

@@ -61,12 +61,15 @@
          ContainerHelper.saveAllItems(output, this.items);
          output.store("RecipesUsed", RECIPES_USED_CODEC, this.recipesUsed);
      }
-@@ -214,7 +_,7 @@
+@@ -212,9 +_,10 @@
+ 
+     private static void consumeFuel(NonNullList<ItemStack> items, ItemStack fuel) {
          Item fuelItem = fuel.getItem();
++        // Neo: Query the crafting remainder prior to stack mutation (shrink) in order to grab the correct value
++        ItemStackTemplate remainder = fuel.getCraftingRemainder();
          fuel.shrink(1);
          if (fuel.isEmpty()) {
 -            ItemStackTemplate remainder = fuelItem.getCraftingRemainder();
-+            ItemStackTemplate remainder = fuel.getCraftingRemainder();
              items.set(1, remainder != null ? remainder.create() : ItemStack.EMPTY);
          }
      }

patches/net/minecraft/world/level/block/entity/BrewingStandBlockEntity.java.patch

@@ -8,14 +8,15 @@
          ItemStack ingredient = items.get(3);
          PotionBrewing potionBrewing = level.potionBrewing();
 
-@@ -181,8 +_,9 @@
+@@ -181,8 +_,10 @@
              items.set(dest, potionBrewing.mix(ingredient, items.get(dest)));
          }
 
 +        net.neoforged.neoforge.event.EventHooks.onPotionBrewed(items);
++        // Neo: Query the crafting remainder prior to stack mutation (shrink) in order to grab the correct value
++        ItemStackTemplate remainder = ingredient.getCraftingRemainder();
          ingredient.shrink(1);
 -        ItemStackTemplate remainder = ingredient.getItem().getCraftingRemainder();
-+        ItemStackTemplate remainder = ingredient.getCraftingRemainder();
          if (remainder != null) {
              if (ingredient.isEmpty()) {
                  ingredient = remainder.create();

tests/src/main/java/net/neoforged/neoforge/debug/crafting/CraftingRemainderTests.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) NeoForged and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.neoforged.neoforge.debug.crafting;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.entity.FurnaceBlockEntity;
+import net.neoforged.testframework.DynamicTest;
+import net.neoforged.testframework.annotation.ForEachTest;
+import net.neoforged.testframework.annotation.TestHolder;
+import net.neoforged.testframework.gametest.EmptyTemplate;
+import net.neoforged.testframework.gametest.GameTest;
+
+@ForEachTest(groups = "crafting_remainder_tests")
+public interface CraftingRemainderTests {
+    @GameTest
+    @EmptyTemplate
+    @TestHolder(description = "Ensures lava buckets turn into empty buckets when used as fuel", enabledByDefault = true)
+    static void testLavaBucketToEmptyBucket(DynamicTest test) {
+        test.onGameTest(helper -> helper.startSequence()
+                .thenExecute(() -> helper.setBlock(BlockPos.ZERO, Blocks.FURNACE))
+                .thenMap(() -> helper.getBlockEntity(BlockPos.ZERO, FurnaceBlockEntity.class))
+                .thenExecute(furnace -> {
+                    furnace.setItem(/* AbstractFurnaceBlockEntity.SLOT_INPUT */ 0, new ItemStack(Items.RAW_IRON, 64));
+                    furnace.setItem(/* AbstractFurnaceBlockEntity.SLOT_FUEL */ 1, new ItemStack(Items.LAVA_BUCKET));
+                })
+                .thenIdle(1)
+                .thenMap(furnace -> furnace.getItem(/* AbstractFurnaceBlockEntity.SLOT_FUEL */ 1))
+                .thenExecute(fuel -> {
+                    if (!fuel.is(Items.BUCKET)) {
+                        helper.fail("Exepected crafting raminder to be '" + itemName(Items.BUCKET) + "' but found '" + itemName(fuel.getItem()) + "'");
+                    }
+                })
+                .thenSucceed());
+    }
+
+    private static String itemName(Item item) {
+        return item.builtInRegistryHolder().getRegisteredName();
+    }
+}