Fix custom ingredient implementation (#4276)

- Override isEmpty in CustomIngredientImpl
- Override acceptsItem in CustomIngredientImpl
- Override equals and hashCode in CustomIngredientImpl so CustomIngredients can also implement them
  - Adjust the class doc of CustomIngredient to encourage implementors to do so
- Implement Ingredient#hashCode
- Remove incorrect Nullable annotation from ItemStack parameter in CustomIngredientImpl#test
- Implement equals and hashCode on all builtin custom ingredient classes

fabric-recipe-api-v1/src/main/java/net/fabricmc/fabric/api/recipe/v1/ingredient/CustomIngredient.java

@@ -25,7 +25,6 @@
 import net.minecraft.recipe.Ingredient;
 import net.minecraft.recipe.display.SlotDisplay;
 import net.minecraft.registry.entry.RegistryEntry;
-import net.minecraft.registry.entry.RegistryEntryList;
 
 import net.fabricmc.fabric.impl.recipe.ingredient.CustomIngredientImpl;
 
@@ -47,6 +46,9 @@
  * }
  * }</pre>
  *
+ * <p>Implementors of this interface are strongly encouraged to also implement
+ * {@link Object#equals(Object)} and {@link Object#hashCode()}.
+ *
  * @see CustomIngredientSerializer
  */
 public interface CustomIngredient {
@@ -97,11 +99,7 @@ public interface CustomIngredient {
 	 */
 	default SlotDisplay toDisplay() {
 		// Matches the vanilla logic in Ingredient.toDisplay()
-		return RegistryEntryList.of(getMatchingItems().toList()).getStorage().map(
-				SlotDisplay.TagSlotDisplay::new,
-				(itemEntries) -> new SlotDisplay.CompositeSlotDisplay(
-						itemEntries.stream().map(Ingredient::createDisplayWithRemainder).toList()
-				));
+		return new SlotDisplay.CompositeSlotDisplay(getMatchingItems().map(Ingredient::createDisplayWithRemainder).toList());
 	}
 
 	/**

fabric-recipe-api-v1/src/main/java/net/fabricmc/fabric/impl/recipe/ingredient/CustomIngredientImpl.java

@@ -16,6 +16,7 @@
 
 package net.fabricmc.fabric.impl.recipe.ingredient;
 
+import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
@@ -74,6 +75,8 @@ public static CustomIngredientSerializer<?> getSerializer(Identifier identifier)
 	// Actual custom ingredient logic
 
 	private final CustomIngredient customIngredient;
+	@Nullable
+	private List<RegistryEntry<Item>> customMatchingItems;
 
 	public CustomIngredientImpl(CustomIngredient customIngredient) {
 		// We must pass a registry entry list that contains something that isn't air. It doesn't actually get used.
@@ -82,6 +85,14 @@ public CustomIngredientImpl(CustomIngredient customIngredient) {
 		this.customIngredient = customIngredient;
 	}
 
+	private List<RegistryEntry<Item>> getCustomMatchingItems() {
+		if (customMatchingItems == null) {
+			customMatchingItems = customIngredient.getMatchingItems().toList();
+		}
+
+		return customMatchingItems;
+	}
+
 	@Override
 	public CustomIngredient getCustomIngredient() {
 		return customIngredient;
@@ -94,16 +105,38 @@ public boolean requiresTesting() {
 
 	@Override
 	public Stream<RegistryEntry<Item>> getMatchingItems() {
-		return customIngredient.getMatchingItems();
+		return getCustomMatchingItems().stream();
 	}
 
 	@Override
-	public boolean test(@Nullable ItemStack stack) {
-		return stack != null && customIngredient.test(stack);
+	public boolean isEmpty() {
+		return getCustomMatchingItems().isEmpty();
+	}
+
+	@Override
+	public boolean test(ItemStack stack) {
+		return customIngredient.test(stack);
+	}
+
+	@Override
+	public boolean acceptsItem(RegistryEntry<Item> registryEntry) {
+		return getCustomMatchingItems().contains(registryEntry);
 	}
 
 	@Override
 	public SlotDisplay toDisplay() {
 		return customIngredient.toDisplay();
 	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (this == o) return true;
+		if (!(o instanceof CustomIngredientImpl that)) return false;
+		return customIngredient.equals(that.customIngredient);
+	}
+
+	@Override
+	public int hashCode() {
+		return customIngredient.hashCode();
+	}
 }

fabric-recipe-api-v1/src/main/java/net/fabricmc/fabric/impl/recipe/ingredient/builtin/CombinedIngredient.java

@@ -67,6 +67,18 @@ public SlotDisplay toDisplay() {
 		);
 	}
 
+	@Override
+	public boolean equals(Object o) {
+		if (this == o) return true;
+		if (!(o instanceof CombinedIngredient that)) return false;
+		return ingredients.equals(that.ingredients);
+	}
+
+	@Override
+	public int hashCode() {
+		return ingredients.hashCode();
+	}
+
 	static class Serializer<I extends CombinedIngredient> implements CustomIngredientSerializer<I> {
 		private final Identifier identifier;
 		private final MapCodec<I> codec;

fabric-recipe-api-v1/src/main/java/net/fabricmc/fabric/impl/recipe/ingredient/builtin/ComponentsIngredient.java

@@ -120,6 +120,19 @@ private ComponentChanges getComponents() {
 		return components;
 	}
 
+	@Override
+	public boolean equals(Object o) {
+		if (this == o) return true;
+		if (o == null || getClass() != o.getClass()) return false;
+		ComponentsIngredient that = (ComponentsIngredient) o;
+		return base.equals(that.base) && components.equals(that.components);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(base, components);
+	}
+
 	private static class Serializer implements CustomIngredientSerializer<ComponentsIngredient> {
 		private static final Identifier ID = Identifier.of("fabric", "components");
 		private static final MapCodec<ComponentsIngredient> CODEC = RecordCodecBuilder.mapCodec(instance ->

fabric-recipe-api-v1/src/main/java/net/fabricmc/fabric/impl/recipe/ingredient/builtin/CustomDataIngredient.java

@@ -16,6 +16,7 @@
 
 package net.fabricmc.fabric.impl.recipe.ingredient.builtin;
 
+import java.util.Objects;
 import java.util.stream.Stream;
 
 import com.mojang.serialization.MapCodec;
@@ -40,6 +41,7 @@
 
 public class CustomDataIngredient implements CustomIngredient {
 	public static final CustomIngredientSerializer<CustomDataIngredient> SERIALIZER = new Serializer();
+
 	private final Ingredient base;
 	private final NbtCompound nbt;
 
@@ -95,6 +97,19 @@ private NbtCompound getNbt() {
 		return nbt;
 	}
 
+	@Override
+	public boolean equals(Object o) {
+		if (this == o) return true;
+		if (o == null || getClass() != o.getClass()) return false;
+		CustomDataIngredient that = (CustomDataIngredient) o;
+		return base.equals(that.base) && nbt.equals(that.nbt);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(base, nbt);
+	}
+
 	private static class Serializer implements CustomIngredientSerializer<CustomDataIngredient> {
 		private static final Identifier ID = Identifier.of("fabric", "custom_data");
 

fabric-recipe-api-v1/src/main/java/net/fabricmc/fabric/impl/recipe/ingredient/builtin/DifferenceIngredient.java

@@ -17,6 +17,7 @@
 package net.fabricmc.fabric.impl.recipe.ingredient.builtin;
 
 import java.util.List;
+import java.util.Objects;
 import java.util.stream.Stream;
 
 import com.mojang.serialization.MapCodec;
@@ -74,6 +75,19 @@ private Ingredient getSubtracted() {
 		return subtracted;
 	}
 
+	@Override
+	public boolean equals(Object o) {
+		if (this == o) return true;
+		if (o == null || getClass() != o.getClass()) return false;
+		DifferenceIngredient that = (DifferenceIngredient) o;
+		return base.equals(that.base) && subtracted.equals(that.subtracted);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(base, subtracted);
+	}
+
 	private static class Serializer implements CustomIngredientSerializer<DifferenceIngredient> {
 		private static final Identifier ID = Identifier.of("fabric", "difference");
 		private static final MapCodec<DifferenceIngredient> CODEC = RecordCodecBuilder.mapCodec(instance ->

fabric-recipe-api-v1/src/main/java/net/fabricmc/fabric/mixin/recipe/ingredient/IngredientMixin.java

@@ -26,10 +26,13 @@
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
 
+import net.minecraft.item.Item;
 import net.minecraft.network.RegistryByteBuf;
 import net.minecraft.network.codec.PacketCodec;
 import net.minecraft.recipe.Ingredient;
+import net.minecraft.registry.entry.RegistryEntryList;
 
 import net.fabricmc.fabric.api.recipe.v1.ingredient.CustomIngredient;
 import net.fabricmc.fabric.api.recipe.v1.ingredient.CustomIngredientSerializer;
@@ -44,6 +47,10 @@ public class IngredientMixin implements FabricIngredient {
 	@Final
 	public static Codec<Ingredient> CODEC;
 
+	@Shadow
+	@Final
+	private RegistryEntryList<Item> entries;
+
 	@Inject(method = "<clinit>", at = @At("TAIL"), cancellable = true)
 	private static void injectCodec(CallbackInfo ci) {
 		Codec<CustomIngredient> customIngredientCodec = CustomIngredientImpl.CODEC.dispatch(
@@ -71,4 +78,18 @@ private static void injectCodec(CallbackInfo ci) {
 	private static PacketCodec<RegistryByteBuf, Ingredient> useCustomIngredientPacketCodec(PacketCodec<RegistryByteBuf, Ingredient> original) {
 		return new CustomIngredientPacketCodec(original);
 	}
+
+	@Inject(method = "equals(Ljava/lang/Object;)Z", at = @At("HEAD"))
+	private void onHeadEquals(Object obj, CallbackInfoReturnable<Boolean> cir) {
+		if (obj instanceof CustomIngredientImpl) {
+			// This will only get called when this isn't custom and other is custom, in which case the
+			// ingredients can never be equal.
+			cir.setReturnValue(false);
+		}
+	}
+
+	@Override
+	public int hashCode() {
+		return entries.hashCode();
+	}
 }