NeoForge oracle: export items' data components and armour facts

Each item now carries its default components (vanilla's codecs, 1.21.1's
form), its effective attribute modifiers (armour's come from a method,
not a component), enchantability and repair items, and for armour its
slot, defense, toughness, knockback resistance, equip sound and texture
layers: the ground truth an item port is compared against. The export
also creates its output folder instead of failing to write.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/modpacks.md

@@ -759,7 +759,9 @@ python3 tools/mod_port_harness.py --work <work>      # or --jars/--deps to expor
   namespaces and every vanilla block: the class chain, states, per-state hardness, light, tool
   need, map colour, sounds, outline and collision shapes; drops for hand, diamond tools, shears
   and silk touch; placement on a floor and a wall; BlockSetType and WoodType. Then items (class,
-  stack size, rarity, food), recipes (type, result, count, resolved ingredients) and tags. One run
+  stack size, rarity, food; every default data component in 1.21.1's form, the effective attribute
+  modifiers, enchantability and repair items; armour's slot, defense, toughness, knockback resistance,
+  equip sound and texture layers), recipes (type, result, count, resolved ingredients) and tags. One run
   with the seven mods below takes about 30 s.
 - `crates/horizon-client/examples/mod_port_probe.rs` builds the content root from the carried
   mods and dumps what Horizon's loaders make of the same blocks, drops, recipes and tags.

mods/horizon/src/neoforge-oracle/java/dev/horizonlab/neoforge/FactsExporter.java

@@ -1,6 +1,10 @@
 package dev.horizonlab.neoforge;
 
+import com.google.gson.JsonElement;
 import com.google.gson.stream.JsonWriter;
+import com.mojang.serialization.DataResult;
+import com.mojang.serialization.DynamicOps;
+import com.mojang.serialization.JsonOps;
 import java.io.IOException;
 import java.io.Writer;
 import java.nio.charset.StandardCharsets;
@@ -16,6 +20,7 @@ import java.util.TreeMap;
 import java.util.TreeSet;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Direction;
+import net.minecraft.core.component.TypedDataComponent;
 import net.minecraft.core.registries.BuiltInRegistries;
 import net.minecraft.core.registries.Registries;
 import net.minecraft.resources.ResourceLocation;
@@ -23,10 +28,14 @@ import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.sounds.SoundEvent;
 import net.minecraft.world.InteractionHand;
+import net.minecraft.world.item.ArmorItem;
+import net.minecraft.world.item.ArmorMaterial;
 import net.minecraft.world.item.BlockItem;
 import net.minecraft.world.item.Item;
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.item.Items;
+import net.minecraft.world.item.TieredItem;
+import net.minecraft.world.item.component.ItemAttributeModifiers;
 import net.minecraft.world.item.context.BlockPlaceContext;
 import net.minecraft.world.item.crafting.Ingredient;
 import net.minecraft.world.item.crafting.RecipeHolder;
@@ -346,11 +355,72 @@ public final class FactsExporter {
                     json.name("saturation").value(food.saturation());
                     json.endObject();
                 }
+                itemComponents(item, stack);
                 json.endObject();
             }
             json.endObject();
         }
 
+        // The item's own numbers in 1.21.1's forms: its default components, and what it keeps outside them.
+        void itemComponents(Item item, ItemStack stack) throws IOException {
+            DynamicOps<JsonElement> ops = server.registryAccess().createSerializationContext(JsonOps.INSTANCE);
+            json.name("components");
+            json.beginObject();
+            for (TypedDataComponent<?> c : stack.getComponents()) {
+                var encoded = c.encodeValue(ops).result();
+                if (encoded.isPresent()) {
+                    json.name(BuiltInRegistries.DATA_COMPONENT_TYPE.getKey(c.type()).toString());
+                    json.jsonValue(encoded.get().toString());
+                }
+            }
+            json.endObject();
+            // Armor's come from ArmorItem.getDefaultAttributeModifiers, not a component.
+            raw("attribute_modifiers", ItemAttributeModifiers.CODEC.encodeStart(ops, stack.getAttributeModifiers()));
+            json.name("enchantment_value").value(item.getEnchantmentValue());
+            Ingredient repair = null;
+            if (item instanceof TieredItem tiered) {
+                repair = tiered.getTier().getRepairIngredient();
+            } else if (item instanceof ArmorItem armor) {
+                repair = armor.getMaterial().value().repairIngredient().get();
+            }
+            if (repair != null) {
+                json.name("repair_items");
+                json.beginArray();
+                for (ItemStack s : repair.getItems()) json.value(BuiltInRegistries.ITEM.getKey(s.getItem()).toString());
+                json.endArray();
+            }
+            if (item instanceof ArmorItem armor) {
+                ArmorMaterial material = armor.getMaterial().value();
+                json.name("armor");
+                json.beginObject();
+                json.name("slot").value(armor.getEquipmentSlot().getName());
+                json.name("material").value(armor.getMaterial().unwrapKey().map(k -> k.location().toString()).orElse(""));
+                json.name("defense").value(armor.getDefense());
+                json.name("toughness").value(armor.getToughness());
+                json.name("knockback_resistance").value(material.knockbackResistance());
+                json.name("equip_sound").value(BuiltInRegistries.SOUND_EVENT.getKey(material.equipSound().value()).toString());
+                json.name("layers");
+                json.beginArray();
+                for (ArmorMaterial.Layer layer : material.layers()) {
+                    json.beginObject();
+                    json.name("texture").value(layer.texture(false).toString());
+                    json.name("texture_legs").value(layer.texture(true).toString());
+                    json.name("dyeable").value(layer.dyeable());
+                    json.endObject();
+                }
+                json.endArray();
+                json.endObject();
+            }
+        }
+
+        void raw(String name, DataResult<JsonElement> encoded) throws IOException {
+            var value = encoded.result();
+            if (value.isPresent()) {
+                json.name(name);
+                json.jsonValue(value.get().toString());
+            }
+        }
+
         void recipes() throws IOException {
             json.name("recipes");
             json.beginObject();

tools/neoforge_oracle.py

@@ -215,6 +215,7 @@ def export(args):
     exporter = build(home)
     home, run = instance('export', jars, [*deps, exporter])
     out = Path(args.out).resolve()
+    out.parent.mkdir(parents=True, exist_ok=True)
     out.unlink(missing_ok=True)
     seconds, log = start(home, run, {'horizon.oracle.out': out, 'horizon.oracle.namespaces': namespaces})
     if not out.exists():