fire: Document flammable group, a little code cleanup

game_api.txt

@@ -362,6 +362,8 @@ The farming API allows you to easily register plants and hoes.
 Fire API
 --------
 
+Add group flammable when registering a node to make fire seek for it.
+Add it to an item to make it burn up when dropped in lava or fire.
 New node def property:
 
 `on_burn(pos)`

mods/fire/init.lua

@@ -320,7 +320,7 @@ if fire_enabled then
 		interval = 7,
 		chance = 12,
 		catch_up = false,
-		action = function(pos, node, active_object_count, active_object_count_wider)
+		action = function(pos)
 			local p = minetest.find_node_near(pos, 1, {"air"})
 			if p then
 				minetest.set_node(p, {name = "fire:basic_flame"})
@@ -337,17 +337,18 @@ if fire_enabled then
 		interval = 5,
 		chance = 18,
 		catch_up = false,
-		action = function(pos, node, active_object_count, active_object_count_wider)
+		action = function(pos)
 			local p = minetest.find_node_near(pos, 1, {"group:flammable"})
-			if p then
-				local flammable_node = minetest.get_node(p)
-				local def = minetest.registered_nodes[flammable_node.name]
-				if def.on_burn then
-					def.on_burn(p)
-				else
-					minetest.remove_node(p)
-					minetest.check_for_falling(p)
-				end
+			if not p then
+				return
+			end
+			local flammable_node = minetest.get_node(p)
+			local def = minetest.registered_nodes[flammable_node.name]
+			if def.on_burn then
+				def.on_burn(p)
+			else
+				minetest.remove_node(p)
+				minetest.check_for_falling(p)
 			end
 		end,
 	})