add more fuels

config.lua

@@ -0,0 +1,12 @@
+
+oillamps.burn_resource = {"basic_materials:oil_extract","ethereal:palm_wax","basic_materials:paraffin"}
+oillamps.bexist = false
+oillamps.existing_ressource = {}
+
+-- check that at least one burning ressource exist
+for _,resource in pairs(oillamps.burn_resource) do
+	oillamps.bexist = oillamps.bexist or (minetest.registered_items[resource] ~= nil)
+	if (minetest.registered_items[resource]) then
+		table.insert(oillamps.existing_ressource,resource)
+	end
+end

crafts.lua

@@ -14,14 +14,19 @@ minetest.register_craft({
 	cooktime = 3
 })
 
-minetest.register_craft({
-	output = "basic_materials:oil_extract 2",
-	recipe = {{"group:seed","group:seed"},{"group:seed","group:seed"}},
-})
+if minetest.registered_items["basic_materials:oil_extract"] then
+	minetest.register_craft({
+		output = "basic_materials:oil_extract 2",
+		recipe = {{"group:seed","group:seed"},{"group:seed","group:seed"}},
+	})
+end
 
 -- fill an empty oil lamp with oil extract
-minetest.register_craft({
-	recipe = {{"basic_materials:oil_extract"},{"oillamps:oillampempty"}},
-	output = "oillamps:oillamp 1",
-})
-
+for _,resource in pairs(oillamps.existing_ressource) do
+	if minetest.registered_items[resource] then
+		minetest.register_craft({
+			recipe = {{resource},{"oillamps:oillampempty"}},
+			output = "oillamps:oillamp 1",
+		})
+	end
+end

init.lua

@@ -7,9 +7,14 @@ modname = minetest.get_current_modname(),
 
 minetest.log("action", "[MOD]"..oillamps.modname.." -- start loading ")
 
-dofile(oillamps.modpath .. "/nodes.lua")
-dofile(oillamps.modpath .. "/craftitems.lua")
-dofile(oillamps.modpath .. "/crafts.lua")
+dofile(oillamps.modpath .. "/config.lua")
+if(oillamps.bexist) then
+	dofile(oillamps.modpath .. "/nodes.lua")
+	dofile(oillamps.modpath .. "/craftitems.lua")
+	dofile(oillamps.modpath .. "/crafts.lua")
+else
+	minetest.log("action", "[MOD]"..oillamps.modname.." -- no ressources found -> not defining oil lamps ")
+end
 
 minetest.log("action", "[MOD]"..oillamps.modname.." -- end loading ")
 

mod.conf

@@ -1,3 +1,4 @@
 name = oillamps
-depends = default,basic_materials
+depends = default
+optional_depends = basic_materials,ethereal
 description = Create oillamps with oil from leaves (basic_materials) or create oil with seeds.