PaperMC/paper-server/nms-patches/net/minecraft/world/entity/vehicle/EntityMinecartContainer.patch

--- a/net/minecraft/world/entity/vehicle/EntityMinecartContainer.java
+++ b/net/minecraft/world/entity/vehicle/EntityMinecartContainer.java
@@ -18,6 +18,14 @@
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.level.World;
 
+// CraftBukkit start
+import java.util.List;
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.entity.CraftHumanEntity;
+import org.bukkit.entity.HumanEntity;
+import org.bukkit.inventory.InventoryHolder;
+// CraftBukkit end
+
 public abstract class EntityMinecartContainer extends EntityMinecartAbstract implements ContainerEntity {
 
     private NonNullList<ItemStack> itemStacks;
@@ -25,14 +33,55 @@
     public MinecraftKey lootTable;
     public long lootTableSeed;
 
+    // CraftBukkit start
+    public List<HumanEntity> transaction = new java.util.ArrayList<HumanEntity>();
+    private int maxStack = MAX_STACK;
+
+    public List<ItemStack> getContents() {
+        return this.itemStacks;
+    }
+
+    public void onOpen(CraftHumanEntity who) {
+        transaction.add(who);
+    }
+
+    public void onClose(CraftHumanEntity who) {
+        transaction.remove(who);
+    }
+
+    public List<HumanEntity> getViewers() {
+        return transaction;
+    }
+
+    public InventoryHolder getOwner() {
+        org.bukkit.entity.Entity cart = getBukkitEntity();
+        if(cart instanceof InventoryHolder) return (InventoryHolder) cart;
+        return null;
+    }
+
+    @Override
+    public int getMaxStackSize() {
+        return maxStack;
+    }
+
+    public void setMaxStackSize(int size) {
+        maxStack = size;
+    }
+
+    @Override
+    public Location getLocation() {
+        return getBukkitEntity().getLocation();
+    }
+    // CraftBukkit end
+
     protected EntityMinecartContainer(EntityTypes<?> entitytypes, World world) {
         super(entitytypes, world);
-        this.itemStacks = NonNullList.withSize(36, ItemStack.EMPTY);
+        this.itemStacks = NonNullList.withSize(this.getContainerSize(), ItemStack.EMPTY); // CraftBukkit - SPIGOT-3513
     }
 
     protected EntityMinecartContainer(EntityTypes<?> entitytypes, double d0, double d1, double d2, World world) {
         super(entitytypes, world, d0, d1, d2);
-        this.itemStacks = NonNullList.withSize(36, ItemStack.EMPTY);
+        this.itemStacks = NonNullList.withSize(this.getContainerSize(), ItemStack.EMPTY); // CraftBukkit - SPIGOT-3513
     }
 
     @Override