From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jake Potrebic <jake.m.potrebic@gmail.com>
Date: Sun, 12 May 2024 15:49:36 -0700
Subject: [PATCH] Fix issues with Recipe API


diff --git a/src/main/java/net/minecraft/world/item/crafting/ShapedRecipe.java b/src/main/java/net/minecraft/world/item/crafting/ShapedRecipe.java
index 63cf2b66f51df68aa3f6d98c69368ce454869d64..1bf54b0142fe41b29b21c8b97d3f52bb24a36a92 100644
--- a/src/main/java/net/minecraft/world/item/crafting/ShapedRecipe.java
+++ b/src/main/java/net/minecraft/world/item/crafting/ShapedRecipe.java
@@ -90,7 +90,7 @@ public class ShapedRecipe extends io.papermc.paper.inventory.recipe.RecipeBookEx
         char c = 'a';
         for (Ingredient list : this.pattern.ingredients()) {
             RecipeChoice choice = CraftRecipe.toBukkit(list);
-            if (choice != null) {
+            if (choice != RecipeChoice.empty()) { // Paper
                 recipe.setIngredient(c, choice);
             }
 
diff --git a/src/main/java/org/bukkit/craftbukkit/inventory/CraftRecipe.java b/src/main/java/org/bukkit/craftbukkit/inventory/CraftRecipe.java
index 6ba29875d78ede4aa7978ff689e588f7fed11528..c76c78bb7757d407102271463e14716a1b012deb 100644
--- a/src/main/java/org/bukkit/craftbukkit/inventory/CraftRecipe.java
+++ b/src/main/java/org/bukkit/craftbukkit/inventory/CraftRecipe.java
@@ -29,6 +29,10 @@ public interface CraftRecipe extends Recipe {
         } else if (bukkit instanceof RecipeChoice.ExactChoice) {
             stack = new Ingredient(((RecipeChoice.ExactChoice) bukkit).getChoices().stream().map((mat) -> new net.minecraft.world.item.crafting.Ingredient.ItemValue(CraftItemStack.asNMSCopy(mat))));
             stack.exact = true;
+            // Paper start - support "empty" choices
+        } else if (bukkit == RecipeChoice.empty()) {
+            stack = Ingredient.EMPTY;
+            // Paper end
         } else {
             throw new IllegalArgumentException("Unknown recipe stack instance " + bukkit);
         }
@@ -45,7 +49,7 @@ public interface CraftRecipe extends Recipe {
         list.getItems();
 
         if (list.itemStacks.length == 0) {
-            return null;
+            return RecipeChoice.empty(); // Paper - null breaks API contracts
         }
 
         if (list.exact) {
diff --git a/src/main/java/org/bukkit/craftbukkit/inventory/CraftSmithingTransformRecipe.java b/src/main/java/org/bukkit/craftbukkit/inventory/CraftSmithingTransformRecipe.java
index 37b39a2c696a59b0f52324cc222b83c0c9f341e6..3aec771478a6b17353d57e82baac53dd24779e7b 100644
--- a/src/main/java/org/bukkit/craftbukkit/inventory/CraftSmithingTransformRecipe.java
+++ b/src/main/java/org/bukkit/craftbukkit/inventory/CraftSmithingTransformRecipe.java
@@ -30,6 +30,6 @@ public class CraftSmithingTransformRecipe extends SmithingTransformRecipe implem
     public void addToCraftingManager() {
         ItemStack result = this.getResult();
 
-        MinecraftServer.getServer().getRecipeManager().addRecipe(new RecipeHolder<>(CraftNamespacedKey.toMinecraft(this.getKey()), new net.minecraft.world.item.crafting.SmithingTransformRecipe(this.toNMS(this.getTemplate(), false), this.toNMS(this.getBase(), false), this.toNMS(this.getAddition(), false), CraftItemStack.asNMSCopy(result), this.willCopyDataComponents()))); // Paper - Option to prevent data components copy
+        MinecraftServer.getServer().getRecipeManager().addRecipe(new RecipeHolder<>(CraftNamespacedKey.toMinecraft(this.getKey()), new net.minecraft.world.item.crafting.SmithingTransformRecipe(this.toNMS(this.getTemplate(), false), this.toNMS(this.getBase(), false), this.toNMS(this.getAddition(), false), CraftItemStack.asNMSCopy(result), this.willCopyDataComponents()))); // Paper - Option to prevent data components copy & support empty RecipeChoice
     }
 }
diff --git a/src/main/java/org/bukkit/craftbukkit/inventory/CraftSmithingTrimRecipe.java b/src/main/java/org/bukkit/craftbukkit/inventory/CraftSmithingTrimRecipe.java
index 389fa313f811279091cace76faaabf8bdb0fc94c..61af2fe3534ff67f10310c6c7dec39cff0f93ee3 100644
--- a/src/main/java/org/bukkit/craftbukkit/inventory/CraftSmithingTrimRecipe.java
+++ b/src/main/java/org/bukkit/craftbukkit/inventory/CraftSmithingTrimRecipe.java
@@ -28,6 +28,6 @@ public class CraftSmithingTrimRecipe extends SmithingTrimRecipe implements Craft
 
     @Override
     public void addToCraftingManager() {
-        MinecraftServer.getServer().getRecipeManager().addRecipe(new RecipeHolder<>(CraftNamespacedKey.toMinecraft(this.getKey()), new net.minecraft.world.item.crafting.SmithingTrimRecipe(this.toNMS(this.getTemplate(), false), this.toNMS(this.getBase(), false), this.toNMS(this.getAddition(), false), this.willCopyDataComponents()))); // Paper - Option to prevent data components copy
+        MinecraftServer.getServer().getRecipeManager().addRecipe(new RecipeHolder<>(CraftNamespacedKey.toMinecraft(this.getKey()), new net.minecraft.world.item.crafting.SmithingTrimRecipe(this.toNMS(this.getTemplate(), false), this.toNMS(this.getBase(), false), this.toNMS(this.getAddition(), false), this.willCopyDataComponents()))); // Paper - Option to prevent data components copy & support empty RecipeChoice
     }
 }
diff --git a/src/test/java/io/papermc/paper/inventory/recipe/TestRecipeChoice.java b/src/test/java/io/papermc/paper/inventory/recipe/TestRecipeChoice.java
new file mode 100644
index 0000000000000000000000000000000000000000..45ab2b6d32b29cb663df848534e1aa68293dd613
--- /dev/null
+++ b/src/test/java/io/papermc/paper/inventory/recipe/TestRecipeChoice.java
@@ -0,0 +1,25 @@
+package io.papermc.paper.inventory.recipe;
+
+import java.util.Iterator;
+import org.bukkit.Bukkit;
+import org.bukkit.inventory.Recipe;
+import org.bukkit.support.environment.AllFeatures;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+@AllFeatures
+class TestRecipeChoice {
+
+    @Test
+    void testRecipeChoices() {
+        final Iterator<Recipe> iter = Bukkit.recipeIterator();
+        boolean foundRecipes = false;
+        while (iter.hasNext()) {
+            foundRecipes = true;
+            assertDoesNotThrow(iter::next, "Failed to convert a recipe to Bukkit recipe!");
+        }
+        assertTrue(foundRecipes, "No recipes found!");
+    }
+}
diff --git a/src/test/java/org/bukkit/support/DummyServerHelper.java b/src/test/java/org/bukkit/support/DummyServerHelper.java
index fb4b7625b4ea4b4918ade95829e10e98d1bac70f..cb2b39c562f609375b9e5b20cb5899780995373d 100644
--- a/src/test/java/org/bukkit/support/DummyServerHelper.java
+++ b/src/test/java/org/bukkit/support/DummyServerHelper.java
@@ -92,6 +92,15 @@ public final class DummyServerHelper {
         // Paper end - testing additions
 
         io.papermc.paper.configuration.GlobalConfigTestingBase.setupGlobalConfigForTest(); // Paper - configuration files - setup global configuration test base
+
+        // Paper start - add test for recipe conversion
+        when(instance.recipeIterator()).thenAnswer(ignored ->
+            com.google.common.collect.Iterators.transform(
+                RegistryHelper.getDataPack().getRecipeManager().byType.entries().iterator(),
+                input -> input.getValue().toBukkitRecipe()
+            )
+        );
+        // Paper end - add test for recipe conversion
         return instance;
     }
 }