properly intern accounted stacks

Author: MrHell228

src/main/java/org/spongepowered/common/item/recipe/book/SpongeStackedItemContents.java

@@ -24,8 +24,9 @@
  */
 package org.spongepowered.common.item.recipe.book;
 
-import it.unimi.dsi.fastutil.ints.Int2ReferenceMap;
-import it.unimi.dsi.fastutil.ints.Int2ReferenceOpenHashMap;
+import it.unimi.dsi.fastutil.Hash;
+import it.unimi.dsi.fastutil.objects.Object2ReferenceMap;
+import it.unimi.dsi.fastutil.objects.Object2ReferenceOpenCustomHashMap;
 import net.minecraft.core.Holder;
 import net.minecraft.world.entity.player.StackedContents;
 import net.minecraft.world.entity.player.StackedItemContents;
@@ -37,18 +38,31 @@
 import org.spongepowered.common.bridge.world.item.crafting.PlacementInfoBridge;
 
 import java.util.List;
+import java.util.function.Function;
 
 public class SpongeStackedItemContents extends StackedItemContents {
 
-    private final Int2ReferenceMap<ItemStack> uniqueStackMap = new Int2ReferenceOpenHashMap<>();
+    private static final Hash.Strategy<ItemStack> STACK_HASH_STRATEGY = new Hash.Strategy<>() {
+        @Override
+        public int hashCode(final ItemStack o) {
+            return ItemStack.hashItemAndComponents(o);
+        }
+
+        @Override
+        public boolean equals(final @Nullable ItemStack a, final @Nullable ItemStack b) {
+            return (a == b) || (a != null && b != null && ItemStack.isSameItemSameComponents(a, b));
+        }
+    };
+
+    private final Object2ReferenceMap<ItemStack, ItemStack> stackInterner = new Object2ReferenceOpenCustomHashMap<>(STACK_HASH_STRATEGY);
     private final StackedContents<ItemStack> stackedContents = new StackedContents<>();
 
     @Override
     public void accountStack(final ItemStack stack, final int maxStackSize) {
         if (!stack.isEmpty()) {
-            final ItemStack stackToAccount = this.uniqueStackMap.computeIfAbsent(
-                ItemStack.hashItemAndComponents(stack),
-                $ -> stack);
+            // StackedContents works on Reference2IntMap, so if we meet stack which "same" copy
+            // has already been accounted we would need to provide the stack that was met first.
+            final ItemStack stackToAccount = this.stackInterner.computeIfAbsent(stack, Function.identity());
             this.stackedContents.account(stackToAccount, Math.min(stack.getCount(), maxStackSize));
         }
     }
@@ -88,7 +102,7 @@ public int getBiggestCraftableStack(
 
     @Override
     public void clear() {
-        this.uniqueStackMap.clear();
+        this.stackInterner.clear();
         this.stackedContents.clear();
     }