Grass Path+Farmland→Dirt if below solid, instantly

GROUPS.md

@@ -35,6 +35,7 @@ Please read <http://minecraft.gamepedia.com/Breaking> to learn how digging times
 * `cultivatable=1`: Block will be turned into Dirt by using a hoe on it
 * `flammable`: Block helps spreading fire and gets destroyed by nearby fire (rating doesn't matter)
 * `spreading_dirt_type=1`: A dirt-type block with a cover (e.g. grass) which may spread to neighbor dirt blocks
+* `dirtifies_below_solid=1`: This node turns into dirt immediately when a solid node is placed on top
 * `non_mycelium_plant=1`: A plant which can't grow on mycelium. Placing it on mycelium fails and if mycelium spreads below it, it uproots
 * `soil=1`: Saplings and other small plants can grow on it
 * `soil_sapling=2`: Soil for saplings. Intended to be natural soil. All saplings will grow on this

mods/ITEMS/mcl_core/functions.lua

@@ -445,21 +445,16 @@ minetest.register_abm({
 	end
 })
 
-minetest.register_abm({
-	label = "Turn Grass Path below solid block into Dirt",
-	nodenames = {"mcl_core:grass_path"},
-	neighbors = {"group:solid"},
-	interval = 8,
-	chance = 50,
-	action = function(pos, node)
-		local above = {x = pos.x, y = pos.y + 1, z = pos.z}
-		local name = minetest.get_node(above).name
-		local nodedef = minetest.registered_nodes[name]
-		if name ~= "ignore" and nodedef and (nodedef.groups and nodedef.groups.solid) then
-			minetest.set_node(pos, {name = "mcl_core:dirt"})
+-- Turn Grass Path and similar nodes to Dirt if a solid node is placed above it
+minetest.register_on_placenode(function(pos, newnode, placer, oldnode, itemstack, pointed_thing)
+	if minetest.get_item_group(newnode.name, "solid") ~= 0 then
+		local below = {x=pos.x, y=pos.y-1, z=pos.z}
+		local belownode = minetest.get_node(below)
+		if minetest.get_item_group(belownode.name, "dirtifies_below_solid") == 1 then
+			minetest.set_node(below, {name="mcl_core:dirt"})
 		end
 	end
-})
+end)
 
 --------------------------
 -- Try generate tree   ---

mods/ITEMS/mcl_core/nodes.lua

@@ -407,7 +407,7 @@ minetest.register_node("mcl_core:grass_path", {
 			{-0.5, -0.5, -0.5, 0.5, 0.4375, 0.5},
 		}
 	},
-	groups = {handy=1,shovely=1, cultivatable=2, not_in_creative_inventory=1, },
+	groups = {handy=1,shovely=1, cultivatable=2, dirtifies_below_solid=1, not_in_creative_inventory=1, },
 	sounds = mcl_sounds.node_sound_dirt_defaults({
 		footstep = {name="default_grass_footstep", gain=0.4},
 	}),

mods/ITEMS/mcl_farming/soil.lua

@@ -16,7 +16,7 @@ minetest.register_node("mcl_farming:soil", {
 		local meta = minetest.get_meta(pos)
 		meta:set_int("wet", 0)
 	end,
-	groups = {handy=1,shovely=1, not_in_creative_inventory=1, soil=2, soil_sapling=1 },
+	groups = {handy=1,shovely=1, not_in_creative_inventory=1, dirtifies_below_solid=1, soil=2, soil_sapling=1 },
 	sounds = mcl_sounds.node_sound_dirt_defaults(),
 	_mcl_blast_resistance = 3,
 	_mcl_hardness = 0.6,
@@ -39,7 +39,7 @@ minetest.register_node("mcl_farming:soil_wet", {
 		local meta = minetest.get_meta(pos)
 		meta:set_int("wet", 7)
 	end,
-	groups = {handy=1,shovely=1, not_in_creative_inventory=1, soil=3, soil_sapling=1 },
+	groups = {handy=1,shovely=1, not_in_creative_inventory=1, dirtifies_below_solid=1, soil=3, soil_sapling=1 },
 	sounds = mcl_sounds.node_sound_dirt_defaults(),
 	_mcl_blast_resistance = 3,
 	_mcl_hardness = 0.6,
@@ -120,3 +120,4 @@ minetest.register_abm({
 		end
 	end,
 })
+