Paper/patches/server/0646-Make-hoppers-respect-inventory-max-stack-size.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jake Potrebic <jake.m.potrebic@gmail.com>
Date: Wed, 7 Jul 2021 16:30:17 -0700
Subject: [PATCH] Make hoppers respect inventory max stack size


diff --git a/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java
index 73e505630e8a702e0c46e042c478a9c9c246856c..6907e647ef4d3f5c9c46edb4cf0905844dd1cea9 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java
@@ -436,15 +436,17 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
 
             if (itemstack1.isEmpty()) {
                 // Spigot start - SPIGOT-6693, InventorySubcontainer#setItem
+                ItemStack leftover = ItemStack.EMPTY; // Paper
                 if (!stack.isEmpty() && stack.getCount() > to.getMaxStackSize()) {
+                    leftover = stack; // Paper
                     stack = stack.split(to.getMaxStackSize());
                 }
                 // Spigot end
                 to.setItem(slot, stack);
-                stack = ItemStack.EMPTY;
+                stack = leftover; // Paper
                 flag = true;
             } else if (HopperBlockEntity.canMergeItems(itemstack1, stack)) {
-                int j = stack.getMaxStackSize() - itemstack1.getCount();
+                int j = Math.min(stack.getMaxStackSize(), to.getMaxStackSize()) - itemstack1.getCount(); // Paper
                 int k = Math.min(stack.getCount(), j);
 
                 stack.shrink(k);