craftbukkit/nms-patches/BlockPortal.patch

--- a/net/minecraft/server/BlockPortal.java
+++ b/net/minecraft/server/BlockPortal.java
@@ -2,6 +2,10 @@
 
 import java.util.Random;
 
+// CraftBukkit start
+import org.bukkit.event.entity.EntityPortalEnterEvent;
+// CraftBukkit end
+
 public class BlockPortal extends Block {
 
     public static final BlockStateEnum<EnumDirection.EnumAxis> AXIS = BlockProperties.E;
@@ -32,7 +36,8 @@
             }
 
             if (worldserver.getType(blockposition).a((IBlockAccess) worldserver, blockposition, EntityTypes.ZOMBIFIED_PIGLIN)) {
-                Entity entity = EntityTypes.ZOMBIFIED_PIGLIN.spawnCreature(worldserver, (NBTTagCompound) null, (IChatBaseComponent) null, (EntityHuman) null, blockposition.up(), EnumMobSpawn.STRUCTURE, false, false);
+                // CraftBukkit - set spawn reason to NETHER_PORTAL
+                Entity entity = EntityTypes.ZOMBIFIED_PIGLIN.spawnCreature(worldserver, (NBTTagCompound) null, (IChatBaseComponent) null, (EntityHuman) null, blockposition.up(), EnumMobSpawn.STRUCTURE, false, false, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.NETHER_PORTAL);
 
                 if (entity != null) {
                     entity.resetPortalCooldown();
@@ -54,6 +59,10 @@
     @Override
     public void a(IBlockData iblockdata, World world, BlockPosition blockposition, Entity entity) {
         if (!entity.isPassenger() && !entity.isVehicle() && entity.canPortal()) {
+            // CraftBukkit start - Entity in portal
+            EntityPortalEnterEvent event = new EntityPortalEnterEvent(entity.getBukkitEntity(), new org.bukkit.Location(world.getWorld(), blockposition.getX(), blockposition.getY(), blockposition.getZ()));
+            world.getServer().getPluginManager().callEvent(event);
+            // CraftBukkit end
             entity.d(blockposition);
         }