PaperMC/nms-patches/ContainerHopper.patch

--- a/net/minecraft/server/ContainerHopper.java
+++ b/net/minecraft/server/ContainerHopper.java
@@ -1,9 +1,30 @@
 package net.minecraft.server;
 
+// CraftBukkit start
+import org.bukkit.craftbukkit.inventory.CraftInventory;
+import org.bukkit.craftbukkit.inventory.CraftInventoryView;
+// CraftBukkit end
+
 public class ContainerHopper extends Container {
 
     private final IInventory hopper;
 
+    // CraftBukkit start
+    private CraftInventoryView bukkitEntity = null;
+    private PlayerInventory player;
+
+    @Override
+    public CraftInventoryView getBukkitView() {
+        if (bukkitEntity != null) {
+            return bukkitEntity;
+        }
+
+        CraftInventory inventory = new CraftInventory(this.hopper);
+        bukkitEntity = new CraftInventoryView(this.player.player.getBukkitEntity(), inventory, this);
+        return bukkitEntity;
+    }
+    // CraftBukkit end
+
     public ContainerHopper(int i, PlayerInventory playerinventory) {
         this(i, playerinventory, new InventorySubcontainer(5));
     }
@@ -11,6 +32,7 @@
     public ContainerHopper(int i, PlayerInventory playerinventory, IInventory iinventory) {
         super(Containers.HOPPER, i);
         this.hopper = iinventory;
+        this.player = playerinventory; // CraftBukkit - save player
         a(iinventory, 5);
         iinventory.startOpen(playerinventory.player);
         boolean flag = true;
@@ -35,6 +57,7 @@
 
     @Override
     public boolean canUse(EntityHuman entityhuman) {
+        if (!this.checkReachable) return true; // CraftBukkit
         return this.hopper.a(entityhuman);
     }