use minetest.line_of_sight

mods/default/nodes.lua

@@ -356,6 +356,13 @@ minetest.register_node("default:wooden_planks_2_jungle", {
 
 -- log
 
+minetest.register_node("default:log", {
+	description = "Log",
+	tiles = {"default_log_top.png","default_log_top.png","default_log.png"},
+	groups = {choppy = 3},
+	sounds = default.sounds.wood(),
+})
+
 minetest.register_node("default:log_1", {
 	description = "Log (thick)",
 	tiles = {"default_log_top.png","default_log_top.png","default_log.png"},

mods/mobs/init.lua

@@ -66,9 +66,12 @@ function mobs.register_mob(name, def)
 						end
 						self.object:setyaw(yaw)
 
-						found = true
-						obj:punch(self.object, 10, def.dmg, nil)
-						break
+
+						if minetest.line_of_sight(self.object:getpos(), obj:getpos(), 1) then
+							obj:punch(self.object, 10, def.dmg, nil)
+							found = true
+							break
+						end
 					end
 				end