Modify mcl_util.select_stack to allow specifying the number of items that will be moved, modify hopper on_try_push functions to specify only 1 item will be moved at a time, general cleanup of touched code (reduce indent - 1 place, break filter functions out of function call parameter - 4 places)

mods/CORE/mcl_util/init.lua

@@ -257,12 +257,21 @@ end
 ---@param dst_inventory InvRef Destination inventory to push to
 ---@param dst_list string Name of destination inventory list to push to
 ---@param condition? fun(stack: ItemStack) Condition which items are allowed to be transfered.
+---@param count? integer Number of items to try to transfer at once
 ---@return integer Item stack number to be transfered
-function mcl_util.select_stack(src_inventory, src_list, dst_inventory, dst_list, condition)
+function mcl_util.select_stack(src_inventory, src_list, dst_inventory, dst_list, condition, count)
 	local src_size = src_inventory:get_size(src_list)
 	local stack
 	for i = 1, src_size do
 		stack = src_inventory:get_stack(src_list, i)
+
+		-- Allow for partial stack movement
+		if count then
+			local new_stack = ItemStack(stack)
+			new_stack:set_count(count)
+			stack = new_stack
+		end
+
 		if not stack:is_empty() and dst_inventory:room_for_item(dst_list, stack) and ((condition == nil or condition(stack))) then
 			return i
 		end
@@ -280,9 +289,13 @@ end
 -- Returns true on success and false on failure
 -- Possible failures: No item in source slot, destination inventory full
 function mcl_util.move_item(source_inventory, source_list, source_stack_id, destination_inventory, destination_list)
-	if not source_inventory:is_empty(source_list) then
+	-- Can't move items we don't have
+	if source_inventory:is_empty(source_list) then return false end
+
+	-- Can't move from an empty stack
 	local stack = source_inventory:get_stack(source_list, source_stack_id)
-		if not stack:is_empty() then
+	if stack:is_empty() then return false end
+
 	local new_stack = ItemStack(stack)
 	new_stack:set_count(1)
 	if not destination_inventory:room_for_item(destination_list, new_stack) then
@@ -293,9 +306,6 @@ function mcl_util.move_item(source_inventory, source_list, source_stack_id, dest
 	destination_inventory:add_item(destination_list, new_stack)
 	return true
 end
-	end
-	return false
-end
 
 --- Try pushing item from hopper inventory to destination inventory
 ---@param pos Vector
@@ -314,25 +324,23 @@ function mcl_util.hopper_push(pos, dst_pos)
 	local dst_list = 'main'
 	local dst_inv, stack_id
 
+	-- Find a inventory stack in the destination
 	if dst_def._mcl_hoppers_on_try_push then
 		dst_inv, dst_list, stack_id = dst_def._mcl_hoppers_on_try_push(dst_pos, pos, hop_inv, hop_list)
 	else
 		local dst_meta = minetest.get_meta(dst_pos)
 		dst_inv = dst_meta:get_inventory()
-		stack_id = mcl_util.select_stack(hop_inv, hop_list, dst_inv, dst_list)
+		stack_id = mcl_util.select_stack(hop_inv, hop_list, dst_inv, dst_list, nil, 1)
 	end
+	if not stack_id then return false end
 
-	if stack_id ~= nil then
+	-- Move the item
 	local ok = mcl_util.move_item(hop_inv, hop_list, stack_id, dst_inv, dst_list)
 	if dst_def._mcl_hoppers_on_after_push then
 		dst_def._mcl_hoppers_on_after_push(dst_pos)
 	end
-		if ok then
-			return true
-		end
-	end
 
-	return false
+	return ok
 end
 
 -- Try pulling from source inventory to hopper inventory
@@ -357,7 +365,7 @@ function mcl_util.hopper_pull(pos, src_pos)
 	else
 		local src_meta = minetest.get_meta(src_pos)
 		src_inv = src_meta:get_inventory()
-		stack_id = mcl_util.select_stack(src_inv, src_list, hop_inv, hop_list)
+		stack_id = mcl_util.select_stack(src_inv, src_list, hop_inv, hop_list, nil, 1)
 	end
 
 	if stack_id ~= nil then

mods/ITEMS/mcl_books/init.lua

@@ -475,8 +475,11 @@ minetest.register_node("mcl_books:bookshelf", {
 	_mcl_hoppers_on_try_push = function(pos, hop_pos, hop_inv, hop_list)
 		local meta = minetest.get_meta(pos)
 		local inv = meta:get_inventory()
-		return inv, "main", mcl_util.select_stack(hop_inv, hop_list, inv, "main",
+		local filter = function(stack)
-				function(stack) return minetest.get_item_group(stack:get_name(), "book") == 1 or stack:get_name() == "mcl_enchanting:book_enchanted" end)
+			return minetest.get_item_group(stack:get_name(), "book") == 1 or
+			       stack:get_name() == "mcl_enchanting:book_enchanted"
+		end
+		return inv, "main", mcl_util.select_stack(hop_inv, hop_list, inv, "main", filter, 1)
 	end,
 })
 

mods/ITEMS/mcl_brewing/init.lua

@@ -379,16 +379,27 @@ end
 local function hoppers_on_try_push(pos, hop_pos, hop_inv, hop_list)
 	local meta = minetest.get_meta(pos)
 	local inv = meta:get_inventory()
-	if math.abs(pos.y - hop_pos.y) > math.abs(pos.x - hop_pos.x) and math.abs(pos.y - hop_pos.y) > math.abs(pos.z - hop_pos.z) then
+
-		return inv, "input", mcl_util.select_stack(hop_inv, hop_list, inv, "input",
+	if math.abs(pos.y - hop_pos.y) > math.abs(pos.x - hop_pos.x) and math.abs(pos.y - hop_pos.y) > math.abs(pos.z - hop_pos.z)
-			function(stack) return minetest.get_item_group(stack:get_name(), "brewitem") == 1 and minetest.get_item_group(stack:get_name(), "bottle") == 0 end)
+	then
+		local filter = function(stack)
+			return minetest.get_item_group(stack:get_name(), "brewitem") == 1 and
+			       minetest.get_item_group(stack:get_name(), "bottle") == 0
+		end
+
+		return inv, "input", mcl_util.select_stack(hop_inv, hop_list, inv, "input", filter, 1)
 	else
-		local stack = mcl_util.select_stack(hop_inv, hop_list, inv, "fuel", function(stack) return stack:get_name() == "mcl_mobitems:blaze_powder" end)
+		local filter = function(stack)
+			return stack:get_name() == "mcl_mobitems:blaze_powder"
+		end
+		local stack = mcl_util.select_stack(hop_inv, hop_list, inv, "fuel", filter, 1 )
 		if stack then
 			return inv, "fuel", stack
 		else
-			return inv, "stand", mcl_util.select_stack(hop_inv, hop_list, inv, "stand",
+			local filter = function(stack)
-				function(stack) return minetest.get_item_group(stack:get_name(), "bottle") == 1 end)
+				return minetest.get_item_group(stack:get_name(), "bottle") == 1
+			end
+			return inv, "stand", mcl_util.select_stack(hop_inv, hop_list, inv, "stand", filter, 1)
 		end
 	end
 end

mods/ITEMS/mcl_chests/init.lua

@@ -760,7 +760,7 @@ local function register_chest(basename, desc, longdesc, usagehelp, tt_help, tile
 		_mcl_hoppers_on_try_push = function(pos, hop_pos, hop_inv, hop_list)
 			local meta = minetest.get_meta(pos)
 			local inv = meta:get_inventory()
-			local stack_id = mcl_util.select_stack(hop_inv, hop_list, inv, "main")
+			local stack_id = mcl_util.select_stack(hop_inv, hop_list, inv, "main", null, 1)
 			if stack_id ~= nil then
 				return inv, "main", stack_id
 			end
@@ -768,7 +768,7 @@ local function register_chest(basename, desc, longdesc, usagehelp, tt_help, tile
 			local pos_other = mcl_util.get_double_container_neighbor_pos(pos, node.param2, "left")
 			local meta_other = minetest.get_meta(pos_other)
 			local inv_other = meta_other:get_inventory()
-			stack_id = mcl_util.select_stack(hop_inv, hop_list, inv_other, "main")
+			stack_id = mcl_util.select_stack(hop_inv, hop_list, inv_other, "main", null, 1)
 			return inv_other, "main", stack_id
 		end,
 	})
@@ -955,13 +955,13 @@ local function register_chest(basename, desc, longdesc, usagehelp, tt_help, tile
 			local pos_other = mcl_util.get_double_container_neighbor_pos(pos, node.param2, "right")
 			local meta_other = minetest.get_meta(pos_other)
 			local inv_other = meta_other:get_inventory()
-			local stack_id = mcl_util.select_stack(hop_inv, hop_list, inv_other, "main")
+			local stack_id = mcl_util.select_stack(hop_inv, hop_list, inv_other, "main", null, 1)
 			if stack_id ~= nil then
 				return inv_other, "main", stack_id
 			end
 			local meta = minetest.get_meta(pos)
 			local inv = meta:get_inventory()
-			stack_id = mcl_util.select_stack(hop_inv, hop_list, inv, "main")
+			stack_id = mcl_util.select_stack(hop_inv, hop_list, inv, "main", null, 1)
 			return inv, "main", stack_id
 		end,
 	})
@@ -1522,7 +1522,7 @@ for color, desc in pairs(boxtypes) do
 		_mcl_hoppers_on_try_push = function(pos, hop_pos, hop_inv, hop_list)
 			local meta = minetest.get_meta(pos)
 			local inv = meta:get_inventory()
-			return inv, "main", mcl_util.select_stack(hop_inv, hop_list, inv, "main", mcl_chests.is_not_shulker_box)
+			return inv, "main", mcl_util.select_stack(hop_inv, hop_list, inv, "main", mcl_chests.is_not_shulker_box, 1)
 		end,
 	})
 

mods/ITEMS/mcl_composters/init.lua

@@ -238,7 +238,7 @@ minetest.register_node("mcl_composters:composter", {
 	_mcl_hoppers_on_try_push = function(pos, hop_pos, hop_inv, hop_list)
 		local meta = minetest.get_meta(pos)
 		local inv = meta:get_inventory()
-		return inv, "src", mcl_util.select_stack(hop_inv, hop_list, inv, "src", hopper_push_condition)
+		return inv, "src", mcl_util.select_stack(hop_inv, hop_list, inv, "src", hopper_push_condition, 1)
 	end,
 	_mcl_hoppers_on_after_push = function(pos)
 		local meta = minetest.get_meta(pos)
@@ -293,7 +293,7 @@ local function register_filled_composter(level)
 		_mcl_hoppers_on_try_push = function(pos, hop_pos, hop_inv, hop_list)
 			local meta = minetest.get_meta(pos)
 			local inv = meta:get_inventory()
-			return inv, "src", mcl_util.select_stack(hop_inv, hop_list, inv, "src", hopper_push_condition)
+			return inv, "src", mcl_util.select_stack(hop_inv, hop_list, inv, "src", hopper_push_condition, 1)
 		end,
 		_mcl_hoppers_on_after_push = function(pos)
 			local meta = minetest.get_meta(pos)

mods/ITEMS/mcl_furnaces/init.lua

@@ -466,9 +466,9 @@ function mcl_furnaces.hoppers_on_try_push(pos, hop_pos, hop_inv, hop_list)
 	local meta = minetest.get_meta(pos)
 	local inv = meta:get_inventory()
 	if math.abs(pos.y - hop_pos.y) > math.abs(pos.x - hop_pos.x) and math.abs(pos.y - hop_pos.y) > math.abs(pos.z - hop_pos.z) then
-		return inv, "src", mcl_util.select_stack(hop_inv, hop_list, inv, "src")
+		return inv, "src", mcl_util.select_stack(hop_inv, hop_list, inv, "src", nil, 1)
 	else
-		return inv, "fuel", mcl_util.select_stack(hop_inv, hop_list, inv, "fuel", mcl_util.is_fuel)
+		return inv, "fuel", mcl_util.select_stack(hop_inv, hop_list, inv, "fuel", mcl_util.is_fuel, 1)
 	end
 end