Adds preconditions

internal.lua

@@ -19,3 +19,15 @@ local function get_node_definition()
 end
 
 function yl_canned_food.get_node_definition() return get_node_definition() end
+
+local function can_set(pos)
+    local light = minetest.get_node_light(pos) 
+    if (light and light > 5) then
+        return false
+    end
+    return true
+end
+
+function yl_canned_food.can_set(pos)
+    return can_set(pos)
+end

item_melon.lua

@@ -24,10 +24,10 @@ table.insert(stages, {
     duration = 10,
     --duration = "10",
     next_stages = {
-        { "yl_canned_food:melon_jam_3", 50 },
-        { "yl_canned_food:melon_jam_4", 50 },
-        { "default:cobble", 50 }
-    },
+        { "yl_canned_food:melon_jam_3", 50, yl_canned_food.can_set},
+        { "yl_canned_food:melon_jam_4", 50},
+        { "default:cobble", 50, yl_canned_food.can_set}
+    },  
     --node definition
     tiles = {"yl_canned_food_melon_jam_2.png"},
     description = "Awesome melon jam Stage 2",