Attempt to fix chest minecarts, at least for 5.9 (#4684)

Not using the `RecheckCartHack` on >5.9 seems to help with #4670 - not tested on older minetest; chest minecarts might still be empty there when the block is unloaded in the meantime. For <5.9, maybe it helps to decrease the time interval, 3 seconds seems to fairly long.

This also makes the minecarts random: 40% minecart, 40% chest minecart, 20% tnt minecart.

Reviewed-on: https://git.minetest.land/VoxeLibre/VoxeLibre/pulls/4684
Reviewed-by: the-real-herowl <the-real-herowl@noreply.git.minetest.land>
Co-authored-by: kno10 <erich.schubert@gmail.com>
Co-committed-by: kno10 <erich.schubert@gmail.com>

mods/MAPGEN/tsm_railcorridors/gameconfig.lua

@@ -36,7 +36,11 @@ else
 	end
 end
 
-tsm_railcorridors.carts = { "mcl_minecarts:chest_minecart" }
+tsm_railcorridors.carts = {
+	"mcl_minecarts:minecart", "mcl_minecarts:minecart",
+	"mcl_minecarts:chest_minecart", "mcl_minecarts:chest_minecart",
+	"mcl_minecarts:tnt_minecart"
+}
 
 -- This is called after a spawner has been placed by the game.
 -- Use this to properly set up the metadata and stuff.
@@ -54,9 +58,11 @@ end
 function tsm_railcorridors.on_construct_cart(_, cart, pr_carts)
 	local l = cart:get_luaentity()
 	local inv = mcl_entity_invs.load_inv(l,27)
+	if inv then -- otherwise probably not a chest minecart
 		local items = tsm_railcorridors.get_treasures(pr_carts)
 		mcl_loot.fill_inventory(inv, "main", items, pr_carts)
 		mcl_entity_invs.save_inv(l)
+	end
 end
 
 -- Fallback function. Returns a random treasure. This function is called for chests

mods/MAPGEN/tsm_railcorridors/init.lua

@@ -397,7 +397,9 @@ end
 -- This is a workaround thanks to the fact that minetest.add_entity is unreliable as fuck
 -- See: https://github.com/minetest/minetest/issues/4759
 -- FIXME: Kill this horrible hack with fire as soon you can.
-local function RecheckCartHack(params)
+local RecheckCartHack = nil
+if not minetest.features.random_state_restore then -- proxy for minetest > 5.9.0, this feature will not be removed
+RecheckCartHack = function(params)
 	local pos = params[1]
 	local cart_id = params[2]
 	-- Find cart
@@ -412,6 +414,7 @@ local function RecheckCartHack(params)
 	end
 	minetest.log("info", "[tsm_railcorridors] Cart spawn FAILED: "..minetest.pos_to_string(pos))
 end
+end
 
 -- Try to place a cobweb.
 -- pos: Position of cobweb
@@ -935,13 +938,17 @@ local function spawn_carts()
 			-- See <https://github.com/minetest/minetest/issues/4759>
 			local cart_id = tsm_railcorridors.carts[cart_type]
 			minetest.log("info", "[tsm_railcorridors] Cart spawn attempt: "..minetest.pos_to_string(cpos))
-			minetest.add_entity(cpos, cart_id)
+			local obj = minetest.add_entity(cpos, cart_id)
 
 			-- This checks if the cart is actually spawned, it's a giant hack!
 			-- Note that the callback function is also called there.
 			-- TODO: Move callback function to this position when the
 			-- minetest.add_entity bug has been fixed (supposedly in 5.9.0?)
+			if RecheckCartHack then
 				minetest.after(3, RecheckCartHack, {cpos, cart_id})
+			else
+				tsm_railcorridors.on_construct_cart(cpos, obj, pr_carts)
+			end
 		end
 	end
 	carts_table = {}