Add reverse tag cache, to make looking up tags for items/blocks/etc.. less costly.

src/main/java/net/minecraftforge/common/extensions/IForgeBlock.java

@@ -21,6 +21,7 @@ package net.minecraftforge.common.extensions;
 
 import java.util.Collection;
 import java.util.Optional;
+import java.util.Set;
 import java.util.function.Predicate;
 
 import javax.annotation.Nullable;
@@ -28,11 +29,9 @@ import javax.annotation.Nullable;
 import net.minecraft.block.Block;
 import net.minecraft.block.BedBlock;
 import net.minecraft.block.FarmlandBlock;
-import net.minecraft.block.FenceBlock;
 import net.minecraft.block.FireBlock;
 import net.minecraft.block.HorizontalBlock;
 import net.minecraft.block.IBeaconBeamColorProvider;
-import net.minecraft.block.StainedGlassBlock;
 import net.minecraft.block.ITileEntityProvider;
 import net.minecraft.block.SoundType;
 import net.minecraft.block.material.Material;
@@ -52,7 +51,6 @@ import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.entity.projectile.WitherSkullEntity;
 import net.minecraft.fluid.IFluidState;
 import net.minecraft.block.Blocks;
-import net.minecraft.item.Items;
 import net.minecraft.potion.Effects;
 import net.minecraft.item.DyeColor;
 import net.minecraft.item.Item;
@@ -65,7 +63,6 @@ import net.minecraft.tileentity.TileEntity;
 import net.minecraft.util.BlockRenderLayer;
 import net.minecraft.util.Direction;
 import net.minecraft.util.Hand;
-import net.minecraft.util.NonNullList;
 import net.minecraft.util.ResourceLocation;
 import net.minecraft.util.Rotation;
 import net.minecraft.util.math.BlockPos;
@@ -86,6 +83,7 @@ import net.minecraftforge.common.ForgeHooks;
 import net.minecraftforge.common.IPlantable;
 import net.minecraftforge.common.ToolType;
 
+@SuppressWarnings("deprecation")
 public interface IForgeBlock
 {
     default Block getBlock()
@@ -177,7 +175,6 @@ public interface IForgeBlock
      * @param state State of the current block
      * @return True if block has a tile entity, false otherwise
      */
-    @SuppressWarnings("deprecation")
     default boolean hasTileEntity(BlockState state)
     {
         return this instanceof ITileEntityProvider;
@@ -192,7 +189,6 @@ public interface IForgeBlock
      * @param world The world to create the TE in
      * @return A instance of a class extending TileEntity
      */
-    @SuppressWarnings("deprecation")
     @Nullable
     default TileEntity createTileEntity(BlockState state, IBlockReader world)
     {
@@ -606,7 +602,6 @@ public interface IForgeBlock
        return 0;
     }
 
-    @SuppressWarnings("deprecation")
     default BlockState rotate(BlockState state, IWorld world, BlockPos pos, Rotation direction)
     {
         return state.rotate(direction);
@@ -855,7 +850,6 @@ public interface IForgeBlock
      * @param hand The player hand used to place this block
      * @return The state to be placed in the world
      */
-    @SuppressWarnings("deprecation")
     default BlockState getStateForPlacement(BlockState state, Direction facing, BlockState state2, IWorld world, BlockPos pos1, BlockPos pos2, Hand hand)
     {
         return this.getBlock().updatePostPlacement(state, facing, state2, world, pos1, pos2);
@@ -905,7 +899,6 @@ public interface IForgeBlock
      * @param face The face that the fire is coming from
      * @return A number ranging from 0 to 300 relating used to determine if the block will be consumed by fire
      */
-    @SuppressWarnings("deprecation")
     default int getFlammability(BlockState state, IBlockReader world, BlockPos pos, Direction face)
     {
         return ((FireBlock)Blocks.FIRE).func_220274_q(state);
@@ -1006,9 +999,14 @@ public interface IForgeBlock
     /**
      * Determines if this block should drop loot when exploded.
      */
-    @SuppressWarnings("deprecation")
     default boolean canDropFromExplosion(BlockState state, IBlockReader world, BlockPos pos, Explosion explosion)
     {
         return state.getBlock().canDropFromExplosion(explosion);
     }
+
+    /**
+     * Retrieves a list of tags names this is known to be associated with.
+     * This should be used in favor of TagCollection.getOwningTags, as this caches the result and automatically updates when the TagCollection changes.
+     */
+    Set<ResourceLocation> getTags();
 }

src/main/java/net/minecraftforge/common/extensions/IForgeFluid.java

@@ -19,6 +19,8 @@
 
 package net.minecraftforge.common.extensions;
 
+import java.util.Set;
+
 import javax.annotation.Nullable;
 
 import net.minecraft.block.material.Material;
@@ -28,6 +30,7 @@ import net.minecraft.fluid.Fluid;
 import net.minecraft.fluid.IFluidState;
 import net.minecraft.tags.Tag;
 import net.minecraft.util.BlockRenderLayer;
+import net.minecraft.util.ResourceLocation;
 import net.minecraft.util.math.AxisAlignedBB;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.Explosion;
@@ -108,4 +111,10 @@ public interface IForgeFluid
     {
         return this.getFluid().getRenderLayer() == layer;
     }
+
+    /**
+     * Retrieves a list of tags names this is known to be associated with.
+     * This should be used in favor of TagCollection.getOwningTags, as this caches the result and automatically updates when the TagCollection changes.
+     */
+    Set<ResourceLocation> getTags();
 }

src/main/java/net/minecraftforge/common/extensions/IForgeItem.java

@@ -28,6 +28,7 @@ import com.google.common.collect.Multimap;
 
 import net.minecraft.block.BlockState;
 import net.minecraft.client.renderer.entity.model.BipedModel;
+import net.minecraft.client.renderer.tileentity.ItemStackTileEntityRenderer;
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.MobEntity;
 import net.minecraft.entity.LivingEntity;
@@ -43,6 +44,7 @@ import net.minecraft.item.ItemStack;
 import net.minecraft.item.ItemUseContext;
 import net.minecraft.nbt.CompoundNBT;
 import net.minecraft.util.ActionResultType;
+import net.minecraft.util.ResourceLocation;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.MathHelper;
 import net.minecraft.world.World;
@@ -759,5 +761,11 @@ public interface IForgeItem
      *         one.
      */
     @OnlyIn(Dist.CLIENT)
-    net.minecraft.client.renderer.tileentity.ItemStackTileEntityRenderer getTileEntityItemStackRenderer();
+    ItemStackTileEntityRenderer getTileEntityItemStackRenderer();
+
+    /**
+     * Retrieves a list of tags names this is known to be associated with.
+     * This should be used in favor of TagCollection.getOwningTags, as this caches the result and automatically updates when the TagCollection changes.
+     */
+    Set<ResourceLocation> getTags();
 }

src/main/java/net/minecraftforge/common/util/ReverseTagWrapper.java

@@ -0,0 +1,55 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2019.
+ *
+ * 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.util;
+
+import java.util.HashSet;
+import java.util.Set;
+import java.util.function.IntSupplier;
+import java.util.function.Supplier;
+
+import net.minecraft.tags.TagCollection;
+import net.minecraft.util.ResourceLocation;
+
+public class ReverseTagWrapper<T>
+{
+    private final T target;
+    private final IntSupplier genSupplier;
+    private final Supplier<TagCollection<T>> colSupplier;
+
+    private int generation = -1;
+    private Set<ResourceLocation> cache = null;
+
+    public ReverseTagWrapper(T target, IntSupplier genSupplier, Supplier<TagCollection<T>> colSupplier)
+    {
+        this.target = target;
+        this.genSupplier = genSupplier;
+        this.colSupplier = colSupplier;
+    }
+
+    public Set<ResourceLocation> getTagNames()
+    {
+        if (cache == null || generation != genSupplier.getAsInt())
+        {
+            this.cache = new HashSet<>(colSupplier.get().getOwningTags(target));
+            this.generation = genSupplier.getAsInt();
+        }
+        return this.cache;
+    }
+}