Paper/nms-patches/SlotFurnaceResult.patch

--- a/net/minecraft/server/SlotFurnaceResult.java
+++ b/net/minecraft/server/SlotFurnaceResult.java
@@ -1,6 +1,10 @@
 package net.minecraft.server;
 
 import javax.annotation.Nullable;
+// CraftBukkit start
+import org.bukkit.entity.Player;
+import org.bukkit.event.inventory.FurnaceExtractEvent;
+// CraftBukkit end
 
 public class SlotFurnaceResult extends Slot {
 
@@ -52,6 +56,18 @@
                 i = j;
             }
 
+            // CraftBukkit start - fire FurnaceExtractEvent
+            Player player = (Player) a.getBukkitEntity();
+            TileEntityFurnace furnace = ((TileEntityFurnace) this.inventory);
+            org.bukkit.block.Block block = a.world.getWorld().getBlockAt(furnace.position.getX(), furnace.position.getY(), furnace.position.getZ());
+
+            if (b != 0) {
+                FurnaceExtractEvent event = new FurnaceExtractEvent(player, block, org.bukkit.craftbukkit.util.CraftMagicNumbers.getMaterial(itemstack.getItem()), b, i);
+                a.world.getServer().getPluginManager().callEvent(event);
+                i = event.getExpToDrop();
+            }
+            // CraftBukkit end
+
             while (i > 0) {
                 j = EntityExperienceOrb.getOrbValue(i);
                 i -= j;