PaperMC/paper-server/nms-patches/net/minecraft/world/entity/npc/EntityVillagerTrader.patch

--- a/net/minecraft/world/entity/npc/EntityVillagerTrader.java
+++ b/net/minecraft/world/entity/npc/EntityVillagerTrader.java
@@ -47,6 +47,14 @@
 import net.minecraft.world.phys.Vec3D;
 import org.apache.commons.lang3.tuple.Pair;
 
+// CraftBukkit start
+import org.bukkit.Bukkit;
+import org.bukkit.craftbukkit.inventory.CraftMerchantRecipe;
+import org.bukkit.entity.AbstractVillager;
+import org.bukkit.event.entity.EntityRemoveEvent;
+import org.bukkit.event.entity.VillagerAcquireTradeEvent;
+// CraftBukkit end
+
 public class EntityVillagerTrader extends EntityVillagerAbstract {
 
     private static final int NUMBER_OF_TRADE_OFFERS = 5;
@@ -56,6 +64,7 @@
 
     public EntityVillagerTrader(EntityTypes<? extends EntityVillagerTrader> entitytypes, World world) {
         super(entitytypes, world);
+        this.setDespawnDelay(48000); // CraftBukkit - set default from MobSpawnerTrader
     }
 
     @Override
@@ -136,7 +145,16 @@
                 MerchantRecipe merchantrecipe = villagertrades_imerchantrecipeoption.getOffer(this, this.random);
 
                 if (merchantrecipe != null) {
-                    merchantrecipelist.add(merchantrecipe);
+                    // CraftBukkit start
+                    VillagerAcquireTradeEvent event = new VillagerAcquireTradeEvent((AbstractVillager) getBukkitEntity(), merchantrecipe.asBukkit());
+                    // Suppress during worldgen
+                    if (this.valid) {
+                        Bukkit.getPluginManager().callEvent(event);
+                    }
+                    if (!event.isCancelled()) {
+                        merchantrecipelist.add(CraftMerchantRecipe.fromBukkit(event.getRecipe()).toMinecraft());
+                    }
+                    // CraftBukkit end
                 }
 
             }
@@ -243,7 +261,7 @@
 
     private void maybeDespawn() {
         if (this.despawnDelay > 0 && !this.isTrading() && --this.despawnDelay == 0) {
-            this.discard();
+            this.discard(EntityRemoveEvent.Cause.DESPAWN); // CraftBukkit - add Bukkit remove cause
         }
 
     }