craftbukkit/nms-patches/net/minecraft/world/inventory/ContainerGrindstone.patch

--- a/net/minecraft/world/inventory/ContainerGrindstone.java
+++ b/net/minecraft/world/inventory/ContainerGrindstone.java
@@ -20,8 +20,30 @@
 import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.phys.Vec3D;
 
+// CraftBukkit start
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.inventory.CraftInventoryGrindstone;
+import org.bukkit.craftbukkit.inventory.CraftInventoryView;
+import org.bukkit.entity.Player;
+// CraftBukkit end
+
 public class ContainerGrindstone extends Container {
 
+    // CraftBukkit start
+    private CraftInventoryView bukkitEntity = null;
+    private Player player;
+
+    @Override
+    public CraftInventoryView getBukkitView() {
+        if (bukkitEntity != null) {
+            return bukkitEntity;
+        }
+
+        CraftInventoryGrindstone inventory = new CraftInventoryGrindstone(this.repairSlots, this.resultSlots);
+        bukkitEntity = new CraftInventoryView(this.player, inventory, this);
+        return bukkitEntity;
+    }
+    // CraftBukkit end
     public static final int MAX_NAME_LENGTH = 35;
     public static final int INPUT_SLOT = 0;
     public static final int ADDITIONAL_SLOT = 1;
@@ -47,15 +69,22 @@
                 super.setChanged();
                 ContainerGrindstone.this.slotsChanged(this);
             }
+
+            // CraftBukkit start
+            @Override
+            public Location getLocation() {
+                return containeraccess.getLocation();
+            }
+            // CraftBukkit end
         };
         this.access = containeraccess;
-        this.addSlot(new Slot(this, this.repairSlots, 0, 49, 19) {
+        this.addSlot(new Slot(this.repairSlots, 0, 49, 19) { // CraftBukkit - decompile error
             @Override
             public boolean mayPlace(ItemStack itemstack) {
                 return itemstack.isDamageableItem() || EnchantmentManager.hasAnyEnchantments(itemstack);
             }
         });
-        this.addSlot(new Slot(this, this.repairSlots, 1, 49, 40) {
+        this.addSlot(new Slot(this.repairSlots, 1, 49, 40) { // CraftBukkit - decompile error
             @Override
             public boolean mayPlace(ItemStack itemstack) {
                 return itemstack.isDamageableItem() || EnchantmentManager.hasAnyEnchantments(itemstack);
@@ -113,6 +142,7 @@
             }
         });
         this.addStandardInventorySlots(playerinventory, 8, 84);
+        player = (Player) playerinventory.player.getBukkitEntity(); // CraftBukkit
     }
 
     @Override
@@ -125,7 +155,8 @@
     }
 
     private void createResult() {
-        this.resultSlots.setItem(0, this.computeResult(this.repairSlots.getItem(0), this.repairSlots.getItem(1)));
+        org.bukkit.craftbukkit.event.CraftEventFactory.callPrepareGrindstoneEvent(getBukkitView(), this.computeResult(this.repairSlots.getItem(0), this.repairSlots.getItem(1))); // CraftBukkit
+        sendAllDataToRemote(); // CraftBukkit - SPIGOT-6686: Always send completed inventory to stay in sync with client
         this.broadcastChanges();
     }
 
@@ -227,6 +258,7 @@
 
     @Override
     public boolean stillValid(EntityHuman entityhuman) {
+        if (!this.checkReachable) return true; // CraftBukkit
         return stillValid(this.access, entityhuman, Blocks.GRINDSTONE);
     }