Exception when accessing datapack recipes that were ignored by the server

Expected behavior

I've noticed that datapack recipes that are ignored by minecraft are still detected when accessing it through bukkit.

Here is an example of an ignored recipe. It is because it uses a tag for ingredients, but the tag is empty. So it results in an empty ingredient list:

data/test/recipe/stick.json

{
  "type": "minecraft:crafting_shapeless",
  "category": "misc",
  "ingredients": ["#test:ingredients"],
  "result": {
    "count": 1,
    "id": "minecraft:stick"
  }
}

data/test/tags/item/ingredients.json

{
  "values": []
}

Server logs show this on load:

Recipe namespace:stick can't be placed due to empty ingredients and will be ignored

However, when I use Bukkit.recipeIterator() to iterate through recipes it comes across this recipe and throws and exception:

java.lang.IllegalArgumentException: empty RecipeChoice isn't allowed here
	at org.bukkit.inventory.EmptyRecipeChoice.validate(EmptyRecipeChoice.java:30) ~[paper-api-1.21.9-R0.1-SNAPSHOT.jar:?]
	at org.bukkit.inventory.ShapelessRecipe.addIngredient(ShapelessRecipe.java:135) ~[paper-api-1.21.9-R0.1-SNAPSHOT.jar:?]
	at net.minecraft.world.item.crafting.ShapelessRecipe.toBukkitRecipe(ShapelessRecipe.java:43) ~[paper-1.21.9.jar:1.21.9-37-6950f05]
	at net.minecraft.world.item.crafting.ShapelessRecipe.toBukkitRecipe(ShapelessRecipe.java:19) ~[paper-1.21.9.jar:1.21.9-37-6950f05]
	at net.minecraft.world.item.crafting.RecipeHolder.toBukkitRecipe(RecipeHolder.java:15) ~[paper-1.21.9.jar:1.21.9-37-6950f05]
	at java.base/java.util.Optional.map(Optional.java:260) ~[?:?]
	at org.bukkit.craftbukkit.CraftServer.getRecipe(CraftServer.java:1508) ~[paper-1.21.9.jar:1.21.9-37-6950f05]
	at org.bukkit.Bukkit.getRecipe(Bukkit.java:1155) ~[paper-api-1.21.9-R0.1-SNAPSHOT.jar:?]

Exception is also thrown when calling Bukkit.getRecipe(key) to target that recipe.

Bukkit should be ignoring this recipe when.

Observed/Actual behavior

Bukkit tries to access/rebuild datapack recipes that were ignored by the server.

I also wrote up some quick code to check the nms recipe registry and found that the ignored recipe was NOT in the registry.

Steps/models to reproduce

In datapack: Create an empty item tag.
In datapack: Create a recipe that uses that tag as an ingredient.
In plugin: Try accessing the recipe through Bukkit.getRecipe(key) or Bukkit.recipeIterator().
Launch server.
Notice logs show that it ignored the recipe.
Notice plugin throws exception as it tries to rebuild that recipe.

Plugin and Datapack List

1 basic test plugin, just for testing this issue.
1 basic test datapack, just for testing this issue.

Paper version

This server is running Paper version 1.21.10-84-main@bac3da1 (2025-10-20T02:11:40Z) (Implementing API version 1.21.10-R0.1-SNAPSHOT)
You are running the latest version
Previous version: 1.21.9-37-6950f05 (MC: 1.21.9)

Other

No response

Start with CraftServer.getRecipe and RecipeHolder.toBukkitRecipe in the stack trace, then inspect how ignored recipes reach ShapelessRecipe.toBukkitRecipe and EmptyRecipeChoice.validate. Reproduce the empty-tag datapack case through Bukkit.getRecipe(key) and Bukkit.recipeIterator(); done means ignored recipes are not rebuilt or exposed and neither call throws an exception.