Add EntitySpinAttackEvent

paper-api/src/main/java/io/papermc/paper/event/entity/EntitySpinAttackEvent.java

@@ -0,0 +1,63 @@
+package io.papermc.paper.event.entity;
+
+import org.bukkit.entity.LivingEntity;
+import org.bukkit.event.Cancellable;
+import org.bukkit.event.HandlerList;
+import org.bukkit.event.entity.EntityEvent;
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;
+
+
+/**
+ * Called when an entity is performing a spin attack and touches other entities.
+ * Currently, only player has default damage action which
+ * calls {@link org.bukkit.event.entity.EntityDamageByEntityEvent}.
+ */
+@NullMarked
+public class EntitySpinAttackEvent extends EntityEvent implements Cancellable {
+
+    private static final HandlerList HANDLER_LIST = new HandlerList();
+
+    private boolean cancelled;
+    private final LivingEntity touched;
+
+
+    @ApiStatus.Internal
+    public EntitySpinAttackEvent(final LivingEntity attacker, final LivingEntity touched) {
+        super(attacker);
+        this.touched = touched;
+    }
+
+    @Override
+    public boolean isCancelled() {
+        return cancelled;
+    }
+
+    @Override
+    public void setCancelled(final boolean cancel) {
+        this.cancelled = cancel;
+    }
+
+    @Override
+    public HandlerList getHandlers() {
+        return HANDLER_LIST;
+    }
+
+    public static HandlerList getHandlerList() {
+        return HANDLER_LIST;
+    }
+
+    /**
+     * Gets the entity that gets touched.
+     *
+     * @return the touched entity
+     */
+    public LivingEntity getTouched() {
+        return touched;
+    }
+
+    @Override
+    public LivingEntity getEntity() {
+        return (LivingEntity) super.getEntity();
+    }
+}

paper-server/patches/sources/net/minecraft/world/entity/LivingEntity.java.patch

@@ -1540,6 +1540,22 @@
                  this.doPush(entity1);
              }
          }
+@@ -2956,8 +_,13 @@
+         List<Entity> entities = this.level().getEntities(this, aabb);
+         if (!entities.isEmpty()) {
+             for (Entity entity : entities) {
+-                if (entity instanceof LivingEntity) {
+-                    this.doAutoAttackOnTouch((LivingEntity)entity);
++                if (entity instanceof LivingEntity livingEntity) { // Paper - move LivingEntity conversion ahead
++                    // Paper start - fire EntitySpinAttackEvent
++                    if(!(new io.papermc.paper.event.entity.EntitySpinAttackEvent(this.getBukkitLivingEntity(), livingEntity.getBukkitLivingEntity()).callEvent())){
++                        continue;
++                    }
++                    // Paper end - fire EntitySpinAttackEvent
++                    this.doAutoAttackOnTouch(livingEntity);
+                     this.autoSpinAttackTicks = 0;
+                     this.setDeltaMovement(this.getDeltaMovement().scale(-0.2));
+                     break;
 @@ -2987,9 +_,16 @@
 
      @Override