Paper/paper-server/nms-patches/IInventory.patch

--- a/net/minecraft/server/IInventory.java
+++ b/net/minecraft/server/IInventory.java
@@ -1,6 +1,7 @@
 package net.minecraft.server;
 
 import java.util.Set;
+import org.bukkit.craftbukkit.entity.CraftHumanEntity; // CraftBukkit
 
 public interface IInventory extends Clearable {
 
@@ -16,9 +17,7 @@
 
     void setItem(int i, ItemStack itemstack);
 
-    default int getMaxStackSize() {
-        return 64;
-    }
+    int getMaxStackSize(); // CraftBukkit
 
     void update();
 
@@ -57,4 +56,29 @@
 
         return false;
     }
+
+    // CraftBukkit start
+    java.util.List<ItemStack> getContents();
+
+    void onOpen(CraftHumanEntity who);
+
+    void onClose(CraftHumanEntity who);
+
+    java.util.List<org.bukkit.entity.HumanEntity> getViewers();
+
+    org.bukkit.inventory.InventoryHolder getOwner();
+
+    void setMaxStackSize(int size);
+
+    org.bukkit.Location getLocation();
+
+    default IRecipe getCurrentRecipe() {
+        return null;
+    }
+
+    default void setCurrentRecipe(IRecipe recipe) {
+    }
+
+    int MAX_STACK = 64;
+    // CraftBukkit end
 }