Add ZombieBecomeLeaderEvent

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

@@ -0,0 +1,47 @@
+package io.papermc.paper.event.entity;
+
+import org.bukkit.entity.Zombie;
+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 a zombie becomes a leader zombie and gets extra attributes
+ * and the ability to break door.
+ * <p>
+ * If the event is cancelled, the zombie will not have the extra attributes
+ * or door-breaking ability.
+ */
+
+@NullMarked
+public class ZombieBecomeLeaderEvent extends EntityEvent implements Cancellable {
+
+    private static final HandlerList HANDLER_LIST = new HandlerList();
+    private boolean cancelled;
+
+    @ApiStatus.Internal
+    public ZombieBecomeLeaderEvent(final Zombie zombie) {
+        super(zombie);
+    }
+
+    @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;
+    }
+}

paper-server/patches/sources/net/minecraft/world/entity/monster/zombie/Zombie.java.patch

@@ -229,3 +229,21 @@
          }
      }
 
+@@ -545,7 +_,7 @@
+                 );
+         }
+
+-        if (this.random.nextFloat() < difficultyModifier * 0.05F) {
++        if (this.random.nextFloat() < difficultyModifier * 0.05F && (new io.papermc.paper.event.entity.ZombieBecomeLeaderEvent((org.bukkit.entity.Zombie) this.getBukkitEntity())).callEvent()) { // Paper start - Add ZombieBecomeLeaderEvent
+             this.getAttribute(Attributes.SPAWN_REINFORCEMENTS_CHANCE)
+                 .addOrReplacePermanentModifier(
+                     new AttributeModifier(LEADER_ZOMBIE_BONUS_ID, this.random.nextDouble() * 0.25 + 0.5, AttributeModifier.Operation.ADD_VALUE)
+@@ -559,7 +_,7 @@
+             }
+
+             this.setCanBreakDoors(true);
+-        }
++        } // Paper end - Add ZombieBecomeLeaderEvent
+     }
+
+     protected void randomizeReinforcementsChance() {