More flexible burning API.

Stone, lode, and lux tools now all have their handles burn, and
eject the non-flammable portions of the tool.

Now using a unified on_ignite hook for when flammable things catch
fire.  The call is made BEFORE the node is replaced, and has an
opportunity to look at node metadata and eject anything
non-flammable.

It can be a function, e.g. for shelves, or a static value in the
same format that the function would return (e.g. for lode tools
which need string values for temper substitutions).

If it returns a string or itemstack, it will eject that from the
position where the node burned.  If it returns a table it will
eject all the values of that table.

docs/issues.txt

@@ -9,10 +9,6 @@ ISSUES: Bugs, Cleanup and Refinements
  #    #  #       #    #     #    #       #       #   #   #    #
   ####   #        ####      #    ######  ######  #    #   ####
 
-- Burning consistency.
-	- Add burns_to hook.  Make stone tools burn to stone chip,
-	  make lode/lux tools burn to lode prills.
-
 - Stone doors don't necessarily dig right.  Probably leftover junk
   being inherited in the cloning; need to dig through the properties
   and remove the ones we don't want inherited.

mods/nc_fire/api.lua

@@ -1,6 +1,6 @@
 -- LUALOCALS < ---------------------------------------------------------
-local ipairs, math, minetest, nodecore, pairs, vector
-    = ipairs, math, minetest, nodecore, pairs, vector
+local ItemStack, ipairs, math, minetest, nodecore, pairs, type, vector
+    = ItemStack, ipairs, math, minetest, nodecore, pairs, type, vector
 local math_floor, math_pow, math_random
     = math.floor, math.pow, math.random
 -- LUALOCALS > ---------------------------------------------------------
@@ -15,7 +15,7 @@ do
 	minetest.after(0, function()
 			for k, v in pairs(minetest.registered_items) do
 				if v.groups.flammable and not v.groups.fire_fuel
-				or v.groups.flame or v.name == "air" then
+				and not v.on_ignite or v.groups.flame or v.name == "air" then
 					ventitems[k] = v.groups.flame or 0
 				end
 			end
@@ -50,24 +50,41 @@ do
 	end
 end
 
+local function burneject(pos, stack)
+	if type(stack) == "table" then
+		for _, v in pairs(stack) do
+			burneject(pos, v)
+		end
+		return
+	end
+	if type(stack) == "string" then stack = ItemStack(stack) end
+	if not stack.is_empty then return end
+	if stack and (not stack:is_empty()) then
+		local p = nodecore.scan_flood(pos, 2, nodecore.buildable_to)
+		nodecore.item_eject(p or pos, stack, 1)
+	end
+end
+
 function nodecore.fire_ignite(pos, node)
+	node = node or minetest.get_node(pos)
+	minetest.chat_send_all(node.name)
+	local def = minetest.registered_items[node.name]
+	if def and def.on_ignite then
+		local ign = def.on_ignite
+		if type(ign) == "function" then ign = ign(pos, node) end
+		burneject(pos, ign)
+	end
+
 	local fuel = nodecore.node_group("fire_fuel", pos, node) or 0
 	if fuel < 0 then fuel = 0 end
 	if fuel > nodecore.fire_max then fuel = nodecore.fire_max end
 	fuel = math_floor(fuel)
-	local stack
-	if nodecore.node_group("eject_inv_on_burn", pos, node) then
-		stack = nodecore.stack_get(pos)
-		if stack and (not stack:is_empty()) then
-			local p = nodecore.scan_flood(pos, 2, nodecore.buildable_to)
-			nodecore.item_eject(p or pos, stack, 1)
-		end
-	end
 	if fuel > 0 then
 		minetest.set_node(pos, {name = modname .. ":ember" .. fuel})
 	else
 		minetest.set_node(pos, {name = modname .. ":fire"})
 	end
+
 	minetest.sound_play("nc_fire_ignite", {gain = 1, pos = pos})
 	minetest.sound_play("nc_fire_flamy", {gain = 3, pos = pos})
 	minetest.after(0, function() minetest.check_for_falling(pos) end)

mods/nc_lode/tools.lua

@@ -36,8 +36,10 @@ local function toolhead(name, groups, prills)
 					d.tool_capabilities = toolcap(5)
 				end
 			end,
+			groups = { flammable = 4 },
 			metal_alt_hot = modname .. ":prill_hot " .. prills,
-			tool_wears_to = modname .. ":prill_# " .. prills
+			tool_wears_to = modname .. ":prill_# " .. prills,
+			on_ignite = modname .. ":prill_# " .. prills
 		})
 
 	for _, t in pairs({"annealed", "tempered"}) do

mods/nc_stonework/tools.lua

@@ -54,6 +54,7 @@ local function tooltip(name, group)
 					uses = 0.25,
 					[group] = 3
 				}),
+			on_ignite = modname .. ":chip",
 			sounds = nodecore.sounds("nc_terrain_stony")
 		})
 	nodecore.register_stone_tip_tool({from = wood, to = tool})

mods/nc_woodwork/shelf.lua

@@ -28,7 +28,6 @@ minetest.register_node(modname .. ":shelf", {
 			visinv = 1,
 			flammable = 2,
 			fire_fuel = 3,
-			eject_inv_on_burn = 1,
 			container = 1,
 			totable = 1
 		},
@@ -60,6 +59,9 @@ minetest.register_node(modname .. ":shelf", {
 				return minetest.node_dig(pos, node, digger, ...)
 			end
 		end,
+		on_ignite = function(pos)
+			return nodecore.stack_get(pos)
+		end,
 		stack_allow = function(_, _, stack)
 			local def = minetest.registered_items[stack:get_name()] or {}
 			if def.groups and def.groups.container then return false end