PaperMC/nms-patches/EntityVillager.patch

--- a/net/minecraft/server/EntityVillager.java
+++ b/net/minecraft/server/EntityVillager.java
@@ -3,6 +3,14 @@
 import java.util.Iterator;
 import java.util.Random;
 import javax.annotation.Nullable;
+// CraftBukkit start
+import org.bukkit.Bukkit;
+import org.bukkit.craftbukkit.entity.CraftVillager;
+import org.bukkit.craftbukkit.inventory.CraftMerchantRecipe;
+import org.bukkit.entity.Villager;
+import org.bukkit.event.entity.VillagerAcquireTradeEvent;
+import org.bukkit.event.entity.VillagerReplenishTradeEvent;
+// CraftBukkit end
 
 public class EntityVillager extends EntityAgeable implements IMerchant, NPC {
 
@@ -31,7 +39,7 @@
 
     public EntityVillager(World world, int i) {
         super(world);
-        this.inventory = new InventorySubcontainer("Items", false, 8);
+        this.inventory = new InventorySubcontainer("Items", false, 8, (CraftVillager) this.getBukkitEntity()); // CraftBukkit add argument
         this.setProfession(i);
         this.setSize(0.6F, 1.95F);
         ((Navigation) this.getNavigation()).a(true);
@@ -110,7 +118,14 @@
                         MerchantRecipe merchantrecipe = (MerchantRecipe) iterator.next();
 
                         if (merchantrecipe.h()) {
-                            merchantrecipe.a(this.random.nextInt(6) + this.random.nextInt(6) + 2);
+                            // CraftBukkit start
+                            int bonus = this.random.nextInt(6) + this.random.nextInt(6) + 2;
+                            VillagerReplenishTradeEvent event = new VillagerReplenishTradeEvent((Villager) this.getBukkitEntity(), merchantrecipe.asBukkit(), bonus);
+                            Bukkit.getPluginManager().callEvent(event);
+                            if (!event.isCancelled()) {
+                                merchantrecipe.a(event.getBonus());
+                            }
+                            // CraftBukkit end
                         }
                     }
 
@@ -429,7 +444,20 @@
             for (int l = 0; l < k; ++l) {
                 EntityVillager.IMerchantRecipeOption entityvillager_imerchantrecipeoption = aentityvillager_imerchantrecipeoption3[l];
 
-                entityvillager_imerchantrecipeoption.a(this.trades, this.random);
+                // CraftBukkit start
+                // this is a hack. this must be done because otherwise, if
+                // mojang adds a new type of villager merchant option, it will need to
+                // have event handling added manually. this is better than having to do that.
+                MerchantRecipeList list = new MerchantRecipeList();
+                entityvillager_imerchantrecipeoption.a(list, this.random);
+                for (MerchantRecipe recipe : list) {
+                    VillagerAcquireTradeEvent event = new VillagerAcquireTradeEvent((Villager) getBukkitEntity(), recipe.asBukkit());
+                    Bukkit.getPluginManager().callEvent(event);
+                    if (!event.isCancelled()) {
+                        this.trades.add(CraftMerchantRecipe.fromBukkit(event.getRecipe()).toMinecraft());
+                    }
+                }
+                // CraftBukkit end
             }
         }