Correct crashes/item duplication with dropping carts, start API documentation

mods/ENTITIES/mcl_minecarts/API.md

@@ -0,0 +1,44 @@
+== Cart-Node interactions
+
+As the cart moves thru the environment, it can interact with the surrounding blocks
+thru a number of handlers in the block definitions. All these handlers are defined
+as:
+
+`function(node_position, cart_luaentity, cart_direction, cart_position)`
+
+Arguments:
+`node_position` - position of the node the cart is interacting with
+`cart_luaentity` - The luaentity of the cart that is entering this block. Will
+   be nil for minecarts moving thru unloaded blocks
+`cart_direction` - The direction the cart is moving
+`cart_position` - The location of the cart
+`cart_data` - Information about the cart. This will always be defined.
+
+There are several variants of this handler:
+`_mcl_minecarts_on_enter` - The cart enters this block
+`_mcl_minecarts_on_enter_below` - The cart enters above this block
+`_mcl_minecarts_on_enter_above` - The cart enters below this block
+`_mcl_minecarts_on_enter_side` - The cart enters beside this block
+
+Mods can also define global handlers that are called for every node. These
+handlers are defined as:
+
+`function(node_position, cart_luaentity, cart_direction, node_definition, cart_data)`
+
+Arguments:
+`node_position` - position of the node the cart is interacting with
+`cart_luaentity` - The luaentity of the cart that is entering this block. Will
+   be nil for minecarts moving thru unloaded blocks
+`cart_direction` - The direction the cart is moving
+`cart_position` - The location of the cart
+`cart_data` - Information about the cart. This will always be defined.
+`node_definition` - The definition of the node at `node_position`
+
+The available hooks are:
+`_mcl_minecarts.on_enter` - The cart enters this block
+`_mcl_minecarts.on_enter_below` - The cart enters above this block
+`_mcl_minecarts.on_enter_above` - The cart enters below this block
+`_mcl_minecarts.on_enter_side` - The cart enters beside this block
+
+Only a single function can be installed in each of these handlers. Before installing,
+preserve the existing handler and call it from inside your handler if not `nil`.

mods/ENTITIES/mcl_minecarts/carts.lua

@@ -249,18 +249,10 @@ function DEFAULT_CART_DEF:on_step(dtime)
 	mod.update_cart_orientation(self)
 
 end
-function DEFAULT_CART_DEF:on_death(killer)
-	local staticdata = self._staticdata
+local function kill_cart(staticdata)
+	local pos
 	minetest.log("action", "cart #"..staticdata.uuid.." was killed")
 
-	detach_driver(self)
-
-	-- Detach passenger
-	if self._passenger then
-		local mob = self._passenger.object
-		mob:set_detach()
-	end
-
 	-- Leave nodes
 	if staticdata.attached_at then
 		handle_cart_leave(self, staticdata.attached_at, staticdata.dir )
@@ -268,23 +260,42 @@ function DEFAULT_CART_DEF:on_death(killer)
 		mcl_log("TODO: handle detatched minecart death")
 	end
 
+	-- Handle entity-related items
+	local le = mcl_util.get_luaentity_from_uuid(staticdata.uuid)
+	if le then
+		pos = le.object:get_pos()
+
+		detach_driver(le)
+
+		-- Detach passenger
+		if le._passenger then
+			local mob = le._passenger.object
+			mob:set_detach()
+		end
+	else
+		pos = mod.get_cart_position(staticdata)
+	end
+
+	-- Drop items
+	if not staticdata.dropped then
+		local entity_def = minetest.registered_entities[staticdata.cart_type]
+		if entity_def then
+			local drop = entity_def.drop
+			for d=1, #drop do
+				minetest.add_item(pos, drop[d])
+			end
+
+			-- Prevent item duplication
+			staticdata.dropped = true
+		end
+	end
+
 	-- Remove data
 	destroy_cart_data(staticdata.uuid)
 
-	-- Drop items
-	local drop = self.drop
-	if not killer or not minetest.is_creative_enabled(killer:get_player_name()) then
-		for d=1, #drop do
-			minetest.add_item(self.object:get_pos(), drop[d])
-		end
-	elseif killer and killer:is_player() then
-		local inv = killer:get_inventory()
-		for d=1, #drop do
-			if not inv:contains_item("main", drop[d]) then
-				inv:add_item("main", drop[d])
-			end
-		end
-	end
+end
+function DEFAULT_CART_DEF:on_death(killer)
+	kill_cart(self._staticdata)
 end
 
 -- Place a minecart at pointed_thing
@@ -558,8 +569,14 @@ minetest.register_globalstep(function(dtime)
 				local r = 0.6
 				for _, node_pos in pairs({{r, 0}, {0, r}, {-r, 0}, {0, -r}}) do
 					if minetest.get_node(vector.offset(pos, node_pos[1], 0, node_pos[2])).name == "mcl_core:cactus" then
-						self:on_death()
-						self.object:remove()
+						kill_cart(staticdata)
+						local le = mcl_util.get_luaentity_from_uuid(staticdata.uuid)
+						if le then
+							le:on_death()
+							le.object:remove()
+						else
+							kill_cart(staticdata)
+						end
 						return
 					end
 				end

mods/ENTITIES/mcl_minecarts/movement.lua

@@ -62,11 +62,11 @@ local function handle_cart_enter_exit(staticdata, pos, next_dir, event)
 			-- node-specific hook
 			local hook_name = "_mcl_minecarts_"..event..check[4]
 			local hook = node_def[hook_name]
-			if hook then hook(check_pos, luaentity, next_dir, pos) end
+			if hook then hook(check_pos, luaentity, next_dir, pos, staticdata) end
 
 			-- global minecart hook
 			hook = mcl_minecarts[event..check[4]]
-			if hook then hook(check_pos, luaentity, next_dir, node_def) end
+			if hook then hook(check_pos, luaentity, next_dir, pos, staticdata, node_def) end
 		end
 	end