Deepcopy pointed_thing for after_place_node, give it to on_rightclick too.

builtin/item.lua

@@ -270,12 +270,18 @@ function minetest.item_place_node(itemstack, placer, pointed_thing, param2)
 
 	-- Run callback
 	if def.after_place_node then
-		-- Copy place_to because callback can modify it
+		-- Deepcopy place_to and pointed_thing because callback can modify it
 		local place_to_copy = {x=place_to.x, y=place_to.y, z=place_to.z}
 		local pointed_thing_copy = {
 			type = pointed_thing.type,
-			under = pointed_thing.under,
-			above = pointed_thing.above
+			under = {
+				x = pointed_thing.under.x,
+				y = pointed_thing.under.y,
+				z = pointed_thing.under.z},
+			above = {
+				x = pointed_thing.above.x,
+				y = pointed_thing.above.y,
+				z = pointed_thing.above.z}
 		}
 		if def.after_place_node(place_to_copy, placer, itemstack,
 				pointed_thing_copy) then
@@ -317,7 +323,8 @@ function minetest.item_place(itemstack, placer, pointed_thing, param2)
 		local n = minetest.get_node(pointed_thing.under)
 		local nn = n.name
 		if minetest.registered_nodes[nn] and minetest.registered_nodes[nn].on_rightclick then
-			return minetest.registered_nodes[nn].on_rightclick(pointed_thing.under, n, placer, itemstack) or itemstack, false
+			return minetest.registered_nodes[nn].on_rightclick(pointed_thing.under, n,
+					placer, itemstack, pointed_thing) or itemstack, false
 		end
 	end
 

builtin/misc_helpers.lua

@@ -278,7 +278,7 @@ if minetest then
 		local undef = minetest.registered_nodes[unode.name]
 		if undef and undef.on_rightclick then
 			undef.on_rightclick(pointed_thing.under, node, placer,
-					itemstack)
+					itemstack, pointed_thing)
 			return
 		end
 		local pitch = placer:get_look_pitch()

doc/lua_api.txt

@@ -2205,10 +2205,12 @@ Node definition (register_node)
     on_punch = func(pos, node, puncher),
     ^ default: minetest.node_punch
     ^ By default: does nothing
-    on_rightclick = func(pos, node, clicker, itemstack),
+    on_rightclick = func(pos, node, clicker, itemstack, pointed_thing),
     ^ default: nil
     ^ if defined, itemstack will hold clicker's wielded item
-      Shall return the leftover itemstack
+    ^ Shall return the leftover itemstack
+    ^ Note: pointed_thing can be nil, if a mod calls this function
+     
     on_dig = func(pos, node, digger),
     ^ default: minetest.node_dig
     ^ By default: checks privileges, wears out tool and removes node