PaperMC/nms-patches/EntitySlime.patch

--- a/net/minecraft/server/EntitySlime.java
+++ b/net/minecraft/server/EntitySlime.java
@@ -1,6 +1,9 @@
 package net.minecraft.server;
 
 import javax.annotation.Nullable;
+// CraftBukkit start
+import org.bukkit.event.entity.SlimeSplitEvent;
+// CraftBukkit end
 
 public class EntitySlime extends EntityInsentient implements IMonster {
 
@@ -143,6 +146,18 @@
         if (!this.world.isClientSide && i > 1 && this.getHealth() <= 0.0F) {
             int j = 2 + this.random.nextInt(3);
 
+            // CraftBukkit start
+            SlimeSplitEvent event = new SlimeSplitEvent((org.bukkit.entity.Slime) this.getBukkitEntity(), j);
+            this.world.getServer().getPluginManager().callEvent(event);
+
+            if (!event.isCancelled() && event.getCount() > 0) {
+                j = event.getCount();
+            } else {
+                super.die();
+                return;
+            }
+            // CraftBukkit end
+
             for (int k = 0; k < j; ++k) {
                 float f = ((float) (k % 2) - 0.5F) * (float) i / 4.0F;
                 float f1 = ((float) (k / 2) - 0.5F) * (float) i / 4.0F;
@@ -158,7 +173,7 @@
 
                 entityslime.setSize(i / 2, true);
                 entityslime.setPositionRotation(this.locX + (double) f, this.locY + 0.5D, this.locZ + (double) f1, this.random.nextFloat() * 360.0F, 0.0F);
-                this.world.addEntity(entityslime);
+                this.world.addEntity(entityslime, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.SLIME_SPLIT); // CraftBukkit - SpawnReason
             }
         }