From ea095d3f69e7aadbcdbe5294e5dfc42ba2fe93bf Mon Sep 17 00:00:00 2001
From: DS <ds.desour@proton.me>
Date: Mon, 27 Mar 2023 20:02:23 +0200
Subject: [PATCH] Fix core.item_eat for same-item replace_with_item and split
 stacks before dropping (#13286)

The replace_with_item can be added to the slot of the wield item, which
is afterwards overwritten. This causes item loss.
---
 builtin/game/item.lua | 26 ++++++++++++--------------
 doc/lua_api.txt       |  4 ++--
 2 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/builtin/game/item.lua b/builtin/game/item.lua
index 71126b0a7..17d081f3d 100644
--- a/builtin/game/item.lua
+++ b/builtin/game/item.lua
@@ -390,22 +390,20 @@ function core.do_item_eat(hp_change, replace_with_item, itemstack, user, pointed
 
 	-- Changing hp might kill the player causing mods to do who-knows-what to the
 	-- inventory, so do this before set_hp().
-	if replace_with_item then
-		if itemstack:is_empty() then
-			itemstack:add_item(replace_with_item)
-		else
-			local inv = user:get_inventory()
-			-- Check if inv is null, since non-players don't have one
-			if inv and inv:room_for_item("main", {name=replace_with_item}) then
-				inv:add_item("main", replace_with_item)
-			else
-				local pos = user:get_pos()
-				pos.y = math.floor(pos.y + 0.5)
-				core.add_item(pos, replace_with_item)
-			end
+	replace_with_item = itemstack:add_item(replace_with_item)
+	user:set_wielded_item(itemstack)
+	if not replace_with_item:is_empty() then
+		local inv = user:get_inventory()
+		-- Check if inv is null, since non-players don't have one
+		if inv then
+			replace_with_item = inv:add_item("main", replace_with_item)
 		end
 	end
-	user:set_wielded_item(itemstack)
+	if not replace_with_item:is_empty() then
+		local pos = user:get_pos()
+		pos.y = math.floor(pos.y + 0.5)
+		core.add_item(pos, replace_with_item)
+	end
 
 	user:set_hp(user:get_hp() + hp_change)
 
diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index fdc8e77d8..2179f44b5 100644
--- a/doc/lua_api.txt
+++ b/doc/lua_api.txt
@@ -6082,8 +6082,8 @@ Defaults for the `on_place` and `on_drop` item definition functions
     * Returns `function(itemstack, user, pointed_thing)` as a
       function wrapper for `minetest.do_item_eat`.
     * `replace_with_item` is the itemstring which is added to the inventory.
-      If the player is eating a stack, then replace_with_item goes to a
-      different spot.
+      If the player is eating a stack and `replace_with_item` doesn't fit onto
+      the eaten stack, then the remainings go to a different spot, or are dropped.
 
 Defaults for the `on_punch` and `on_dig` node definition callbacks
 ------------------------------------------------------------------