Add ability to change the itemstack in placenode callbacks

builtin/item.lua

@@ -192,11 +192,15 @@ function minetest.item_place_node(itemstack, placer, pointed_thing)
 	-- Add node and update
 	minetest.env:add_node(place_to, newnode)
 
+	local take_item = true
+
 	-- Run callback
 	if def.after_place_node then
 		-- Copy place_to because callback can modify it
 		local place_to_copy = {x=place_to.x, y=place_to.y, z=place_to.z}
-		def.after_place_node(place_to_copy, placer)
+		if def.after_place_node(place_to_copy, placer, itemstack) then
+			take_item = false
+		end
 	end
 
 	-- Run script hook
@@ -206,10 +210,14 @@ function minetest.item_place_node(itemstack, placer, pointed_thing)
 		local place_to_copy = {x=place_to.x, y=place_to.y, z=place_to.z}
 		local newnode_copy = {name=newnode.name, param1=newnode.param1, param2=newnode.param2}
 		local oldnode_copy = {name=oldnode.name, param1=oldnode.param1, param2=oldnode.param2}
-		callback(place_to_copy, newnode_copy, placer, oldnode_copy)
+		if callback(place_to_copy, newnode_copy, placer, oldnode_copy, itemstack) then
+			take_item = false
+		end
 	end
 
-	itemstack:take_item()
+	if take_item then
+		itemstack:take_item()
+	end
 	return itemstack
 end
 

doc/lua_api.txt

@@ -810,8 +810,9 @@ minetest.register_on_shutdown(func())
 ^ WARNING: If the server terminates abnormally (i.e. crashes), the registered
            callbacks WILL LIKELY NOT BE RUN.  Data should be saved at
            semi-frequent intervals as well as on server shutdown.
-minetest.register_on_placenode(func(pos, newnode, placer, oldnode))
+minetest.register_on_placenode(func(pos, newnode, placer, oldnode, itemstack))
 ^ Called when a node has been placed
+^ If return true no item is taken from itemstack
 ^ Deprecated: Use on_construct or after_place_node in node definition instead
 minetest.register_on_dignode(func(pos, oldnode, digger))
 ^ Called when a node has been dug.
@@ -1405,9 +1406,10 @@ Node definition (register_node)
     ^ Node destructor; always called after removing node
     ^ default: nil
 
-    after_place_node = func(pos, placer),
+    after_place_node = func(pos, placer, itemstack),
     ^ Called after constructing node when node was placed using
       minetest.item_place_node / minetest.env:place_node
+    ^ If return true no item is taken from itemstack
     ^ default: nil
     after_dig_node = func(pos, oldnode, oldmetadata, digger),
     ^ oldmetadata is in table format