[21.1] Pass along interaction had to ItemStack.onEntitySwing

patches/net/minecraft/world/entity/LivingEntity.java.patch

@@ -440,7 +440,7 @@
 
      public void swing(InteractionHand p_21012_, boolean p_21013_) {
 +        ItemStack stack = this.getItemInHand(p_21012_);
-+        if (!stack.isEmpty() && stack.onEntitySwing(this)) return;
++        if (!stack.isEmpty() && stack.onEntitySwing(this, p_21012_)) return;
          if (!this.swinging || this.swingTime >= this.getCurrentSwingDuration() / 2 || this.swingTime < 0) {
              this.swingTime = -1;
              this.swinging = true;

src/main/java/net/neoforged/neoforge/common/extensions/IItemExtension.java

@@ -21,6 +21,7 @@
 import net.minecraft.network.chat.Component;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.util.Mth;
+import net.minecraft.world.InteractionHand;
 import net.minecraft.world.InteractionResult;
 import net.minecraft.world.damagesource.DamageSource;
 import net.minecraft.world.entity.Entity;
@@ -336,12 +337,25 @@ default ResourceLocation getArmorTexture(ItemStack stack, Entity entity, Equipme
      * Called when a entity tries to play the 'swing' animation.
      *
      * @param entity The entity swinging the item.
-     * @return True to cancel any further processing by EntityLiving
+     * @return True to cancel any further processing by {@link LivingEntity}
+     * @deprecated To be replaced with hand sensitive version in 21.2
+     * @see #onEntitySwing(ItemStack, LivingEntity, InteractionHand)
      */
+    @Deprecated(forRemoval = true, since = "21.1")
     default boolean onEntitySwing(ItemStack stack, LivingEntity entity) {
         return false;
     }
 
+    /**
+     * Called when a entity tries to play the 'swing' animation.
+     *
+     * @param entity The entity swinging the item.
+     * @return True to cancel any further processing by {@link LivingEntity}
+     */
+    default boolean onEntitySwing(ItemStack stack, LivingEntity entity, InteractionHand hand) {
+        return onEntitySwing(stack, entity);
+    }
+
     /**
      * Return the itemDamage represented by this ItemStack. Defaults to the Damage
      * entry in the stack NBT, but can be overridden here for other sources.

src/main/java/net/neoforged/neoforge/common/extensions/IItemStackExtension.java

@@ -12,6 +12,7 @@
 import net.minecraft.core.registries.BuiltInRegistries;
 import net.minecraft.network.chat.Component;
 import net.minecraft.stats.Stats;
+import net.minecraft.world.InteractionHand;
 import net.minecraft.world.InteractionResult;
 import net.minecraft.world.damagesource.DamageSource;
 import net.minecraft.world.entity.Entity;
@@ -217,12 +218,26 @@ default boolean canDisableShield(ItemStack shield, LivingEntity entity, LivingEn
      * Called when a entity tries to play the 'swing' animation.
      *
      * @param entity The entity swinging the item.
-     * @return True to cancel any further processing by EntityLiving
+     * @return True to cancel any further processing by {@link LivingEntity}
+     * @deprecated To be replaced with hand sensitive version in 21.2
+     * @see #onEntitySwing(LivingEntity, InteractionHand)
      */
+    @Deprecated(forRemoval = true, since = "21.1")
     default boolean onEntitySwing(LivingEntity entity) {
         return self().getItem().onEntitySwing(self(), entity);
     }
 
+    /**
+     * Called when a entity tries to play the 'swing' animation.
+     *
+     * @param entity The entity swinging the item.
+     * @param hand   The hand the item is held in.
+     * @return True to cancel any further processing by {@link LivingEntity}
+     */
+    default boolean onEntitySwing(LivingEntity entity, InteractionHand hand) {
+        return self().getItem().onEntitySwing(self(), entity, hand);
+    }
+
     /**
      * Called when an entity stops using an item item for any reason.
      *