[1.16.x] Add loot table ID in Global Loot Modifiers (#7428)

src/main/java/net/minecraftforge/common/ForgeHooks.java

@@ -131,6 +131,7 @@ import net.minecraft.world.biome.BiomeGenerationSettings;
 import net.minecraft.world.biome.MobSpawnInfo;
 import net.minecraftforge.common.loot.IGlobalLootModifier;
 import net.minecraftforge.common.loot.LootModifierManager;
+import net.minecraftforge.common.loot.LootTableIdCondition;
 import net.minecraftforge.common.util.BlockSnapshot;
 import net.minecraftforge.common.world.BiomeGenerationSettingsBuilder;
 import net.minecraftforge.common.world.ForgeWorldType;
@@ -861,6 +862,7 @@ public class ForgeHooks
         {
             que.push(new LootTableContext(name, custom));
             ret = gson.fromJson(data, LootTable.class);
+            ret.setLootTableId(name);
             que.pop();
         }
         catch (JsonParseException e)
@@ -1253,16 +1255,42 @@ public class ForgeHooks
     /**
      * All loot table drops should be passed to this function so that mod added effects
      * (e.g. smelting enchantments) can be processed.
+     *
      * @param list The loot generated
      * @param context The loot context that generated that loot
      * @return The modified list
+     *
+     * @deprecated Use {@link #modifyLoot(ResourceLocation, List, LootContext)} instead.
+     *
+     * @implNote This method will use the {@linkplain LootTableIdCondition#UNKNOWN_LOOT_TABLE
+     *           unknown loot table marker} when redirecting.
      */
+    @Deprecated
     public static List<ItemStack> modifyLoot(List<ItemStack> list, LootContext context) {
+        return modifyLoot(LootTableIdCondition.UNKNOWN_LOOT_TABLE, list, context);
+    }
+
+    /**
+     * Handles the modification of loot table drops via the registered Global Loot Modifiers,
+     * so that custom effects can be processed.
+     *
+     * <p>All loot-table generated loot should be passed to this function.</p>
+     *
+     * @param lootTableId The ID of the loot table currently being queried
+     * @param generatedLoot The loot generated by the loot table
+     * @param context The loot context that generated the loot, unmodified
+     * @return The modified list of drops
+     *
+     * @apiNote The given context will be modified by this method to also store the ID of the
+     *          loot table being queried.
+     */
+    public static List<ItemStack> modifyLoot(ResourceLocation lootTableId, List<ItemStack> generatedLoot, LootContext context) {
+        context.setQueriedLootTableId(lootTableId); // In case the ID was set via copy constructor, this will be ignored: intended
         LootModifierManager man = ForgeInternalHandler.getLootModifierManager();
-        for(IGlobalLootModifier mod : man.getAllLootMods()) {
-            list = mod.apply(list, context);
+        for (IGlobalLootModifier mod : man.getAllLootMods()) {
+            generatedLoot = mod.apply(generatedLoot, context);
         }
-        return list;
+        return generatedLoot;
     }
 
     public static List<String> getModPacks()

src/main/java/net/minecraftforge/common/ForgeMod.java

@@ -27,12 +27,15 @@ import net.minecraft.entity.ai.attributes.RangedAttribute;
 import net.minecraft.fluid.Fluid;
 import net.minecraft.item.Items;
 import net.minecraft.util.SoundEvent;
+import net.minecraft.util.registry.Registry;
 import net.minecraft.world.storage.IServerConfiguration;
 import net.minecraft.world.storage.SaveFormat;
 import net.minecraftforge.api.distmarker.Dist;
 import net.minecraftforge.client.ForgeHooksClient;
 import net.minecraftforge.common.data.ExistingFileHelper;
 import net.minecraftforge.common.data.ForgeFluidTagsProvider;
+import net.minecraftforge.common.loot.GlobalLootModifierSerializer;
+import net.minecraftforge.common.loot.LootTableIdCondition;
 import net.minecraftforge.eventbus.api.IEventBus;
 import net.minecraftforge.eventbus.api.SubscribeEvent;
 import net.minecraftforge.fluids.FluidAttributes;
@@ -48,7 +51,6 @@ import net.minecraftforge.registries.DeferredRegister;
 import net.minecraftforge.server.command.EnumArgument;
 import net.minecraftforge.server.command.ModIdArgument;
 import net.minecraftforge.registries.ForgeRegistries;
-import net.minecraftforge.registries.IForgeRegistry;
 import net.minecraftforge.versions.forge.ForgeVersion;
 import net.minecraftforge.versions.mcp.MCPVersion;
 
@@ -288,4 +290,12 @@ public class ForgeMod implements WorldPersistenceHooks.WorldPersistenceHook
         event.getRegistry().register(new ConditionalRecipe.Serializer<IRecipe<?>>().setRegistryName(new ResourceLocation("forge", "conditional")));
 
     }
+
+    @SubscribeEvent //ModBus
+    @SuppressWarnings("unused") // automatically called by Forge
+    public void registerLootData(RegistryEvent.Register<GlobalLootModifierSerializer<?>> event)
+    {
+        // Ignore the event itself: this is done only not to statically initialize our custom LootConditionType
+        Registry.register(Registry.LOOT_CONDITION_TYPE, new ResourceLocation("forge:loot_table_id"), LootTableIdCondition.LOOT_TABLE_ID);
+    }
 }

src/main/java/net/minecraftforge/common/loot/LootTableIdCondition.java

@@ -0,0 +1,93 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2020.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.common.loot;
+
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonSerializationContext;
+import net.minecraft.loot.ILootSerializer;
+import net.minecraft.loot.LootConditionType;
+import net.minecraft.loot.LootContext;
+import net.minecraft.loot.conditions.ILootCondition;
+import net.minecraft.util.JSONUtils;
+import net.minecraft.util.ResourceLocation;
+
+public class LootTableIdCondition implements ILootCondition
+{
+    // TODO Forge Registry at some point?
+    public static final LootConditionType LOOT_TABLE_ID = new LootConditionType(new LootTableIdCondition.Serializer());
+    public static final ResourceLocation UNKNOWN_LOOT_TABLE = new ResourceLocation("forge", "unknown_loot_table");
+
+    private final ResourceLocation targetLootTableId;
+
+    private LootTableIdCondition(final ResourceLocation targetLootTableId)
+    {
+        this.targetLootTableId = targetLootTableId;
+    }
+
+    @Override
+    public LootConditionType func_230419_b_()
+    {
+        return LOOT_TABLE_ID;
+    }
+
+    @Override
+    public boolean test(LootContext lootContext)
+    {
+        return lootContext.getQueriedLootTableId().equals(this.targetLootTableId);
+    }
+
+    public static Builder builder(final ResourceLocation targetLootTableId)
+    {
+        return new Builder(targetLootTableId);
+    }
+
+    public static class Builder implements ILootCondition.IBuilder
+    {
+        private final ResourceLocation targetLootTableId;
+
+        public Builder(ResourceLocation targetLootTableId)
+        {
+            if (targetLootTableId == null) throw new IllegalArgumentException("Target loot table must not be null");
+            this.targetLootTableId = targetLootTableId;
+        }
+
+        @Override
+        public ILootCondition build()
+        {
+            return new LootTableIdCondition(this.targetLootTableId);
+        }
+    }
+
+    public static class Serializer implements ILootSerializer<LootTableIdCondition>
+    {
+        @Override
+        public void serialize(JsonObject object, LootTableIdCondition instance, JsonSerializationContext ctx)
+        {
+            object.addProperty("loot_table_id", instance.targetLootTableId.toString());
+        }
+
+        @Override
+        public LootTableIdCondition deserialize(JsonObject object, JsonDeserializationContext ctx)
+        {
+            return new LootTableIdCondition(new ResourceLocation(JSONUtils.getString(object, "loot_table_id")));
+        }
+    }
+}