PaperMC/paper-server/nms-patches/net/minecraft/world/item/crafting/RecipeSmithing.patch

--- a/net/minecraft/server/RecipeSmithing.java
+++ b/net/minecraft/server/RecipeSmithing.java
@@ -3,6 +3,14 @@
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 
+// CraftBukkit start
+import org.bukkit.craftbukkit.inventory.CraftItemStack;
+import org.bukkit.craftbukkit.inventory.CraftRecipe;
+import org.bukkit.craftbukkit.inventory.CraftSmithingRecipe;
+import org.bukkit.craftbukkit.util.CraftNamespacedKey;
+import org.bukkit.inventory.Recipe;
+// CraftBukkit end
+
 public class RecipeSmithing implements IRecipe<IInventory> {
 
     private final RecipeItemStack a;
@@ -58,6 +66,17 @@
         return Recipes.SMITHING;
     }
 
+    // CraftBukkit start
+    @Override
+    public Recipe toBukkitRecipe() {
+        CraftItemStack result = CraftItemStack.asCraftMirror(this.c);
+
+        CraftSmithingRecipe recipe = new CraftSmithingRecipe(CraftNamespacedKey.fromMinecraft(this.d), result, CraftRecipe.toBukkit(this.a), CraftRecipe.toBukkit(this.b));
+
+        return recipe;
+    }
+    // CraftBukkit end
+
     public static class a implements RecipeSerializer<RecipeSmithing> {
 
         public a() {}