Force-detach minecart driver not attached to cart

If the driver manages to either die in a minecart or attach to some
other object, they may still be taking up space in the cart. No new
driver could enter a cart in such a situation, therefore any driver
of a cart without an attached object must be detached immediately.

mods/ENTITIES/mcl_boats/init.lua

@@ -269,6 +269,25 @@ function boat.on_step(self, dtime, moveresult)
 				self.object:set_animation({x=0, y=40}, paddling_speed, 0, true)
 				self._animation = 1
 			end
+			-- If boat is in a minecart, punch that cart.
+			--
+			-- Why? In Minecraft you can put a boat in a
+			-- minecart and steer the cart from the boat,
+			-- which is quite useful to move mobs around.
+			-- (Minecarts have one seat, boats have two.)
+			--
+			-- No, this is not a bug. Mojang has known it
+			-- for years and they never fixed that “bug”.
+			local parent = self.object:get_attach()
+			if parent then
+				local parent_name =
+					parent:get_luaentity().name
+				if parent_name == "mcl_minecarts:minecart" then
+					-- The driver must punch so
+					-- the steering works here.
+					parent:punch(self._driver, 1, {})
+				end
+			end
 		elseif ctrl.down then
 			-- Backwards
 			self._v = self._v - 0.1 * v_factor
@@ -278,6 +297,7 @@ function boat.on_step(self, dtime, moveresult)
 				self.object:set_animation({x=0, y=40}, -paddling_speed, 0, true)
 				self._animation = -1
 			end
+			-- TODO: If boat is in a minecart, slow cart.
 		else
 			-- Stop paddling animation if no control pressed
 			if self._animation ~= 0 then
@@ -285,13 +305,22 @@ function boat.on_step(self, dtime, moveresult)
 				self._animation = 0
 			end
 		end
-		if ctrl and ctrl.left then
+		-- Rotating a boat while it is attached to another
+		-- object does not work as expected: While the boat
+		-- does not visually rotate, the head of the driver
+		-- rotates as if the boat did actually rotate. That
+		-- looks wrong, therefore no rotation must happen if
+		-- the boat is attached to an object, e.g. a minecart.
+		--
+		-- TODO: Actually rotate boat once someone figures out
+		-- how to rotate an object attached to another object.
+		if ctrl and ctrl.left and not self.object:get_attach() then
 			if self._v < 0 then
 				self.object:set_yaw(yaw - (1 + dtime) * 0.03 * v_factor)
 			else
 				self.object:set_yaw(yaw + (1 + dtime) * 0.03 * v_factor)
 			end
-		elseif ctrl and ctrl.right then
+		elseif ctrl and ctrl.right and not self.object:get_attach() then
 			if self._v < 0 then
 				self.object:set_yaw(yaw + (1 + dtime) * 0.03 * v_factor)
 			else

mods/ENTITIES/mcl_minecarts/init.lua

@@ -12,8 +12,15 @@ local function detach_driver(self)
 	if not self._driver then
 		return
 	end
-	mcl_player.player_attached[self._driver] = nil
-	local player = minetest.get_player_by_name(self._driver)
+	if not self._driver:is_player() then
+		self._pickup_inhibit_timer = 1
+		self._driver:set_detach()
+		self._driver = nil
+		return
+	end
+	local player_name = self._driver:get_player_name()
+	mcl_player.player_attached[player_name] = nil
+	local player = minetest.get_player_by_name(player_name)
 	self._driver = nil
 	self._start_pos = nil
 	if player then
@@ -75,6 +82,7 @@ local function register_entity(entity_id, mesh, textures, drop, on_rightclick, o
 		_old_pos = nil,
 		_old_vel = {x=0, y=0, z=0},
 		_old_switch = 0,
+		_pickup_inhibit_timer = 0, -- how many seconds are mobs and boats not picked up after detaching?
 		_railtype = nil,
 	}
 
@@ -151,7 +159,7 @@ local function register_entity(entity_id, mesh, textures, drop, on_rightclick, o
 		end
 
 		local vel = self.object:get_velocity()
-		if puncher:get_player_name() == self._driver then
+		if self._driver and puncher:get_player_name() == self._driver:get_player_name() then
 			if math.abs(vel.x + vel.z) > 7 then
 				return
 			end
@@ -175,9 +183,35 @@ local function register_entity(entity_id, mesh, textures, drop, on_rightclick, o
 	cart.on_activate_by_rail = on_activate_by_rail
 
 	function cart:on_step(dtime)
+		-- If the driver manages to either die in a minecart
+		-- or attach to some other object, they may still be
+		-- taking up space in the cart. Therefore the driver
+		-- must be detached if the minecart has no children.
+		if self._driver and
+			#self.object:get_children() == 0 then
+			detach_driver(self)
+		end
+
+		if self._pickup_inhibit_timer > 0 then
+			self._pickup_inhibit_timer = self._pickup_inhibit_timer - dtime
+		end
+
+		local entity_name = self.object:get_luaentity().name
+		if entity_name == "mcl_minecarts:minecart" and self._pickup_inhibit_timer <= 0 then
+			for _, obj in ipairs(minetest.get_objects_inside_radius(self.object:get_pos(), 1.3)) do
+				local entity = obj:get_luaentity()
+				if not self._driver and entity and ( entity._cmi_is_mob or entity.name == "mcl_boats:boat" ) and not obj:get_attach() then
+					self._driver = obj
+					obj:set_attach(self.object)
+					break
+				end
+			end
+		end
+
 		local ctrl, player = nil, nil
-		if self._driver then
-			player = minetest.get_player_by_name(self._driver)
+		if self._driver and self._driver:is_player() then
+			local player_name = self._driver:get_player_name()
+			player = minetest.get_player_by_name(player_name)
 			if player then
 				ctrl = player:get_player_control()
 				-- player detach
@@ -446,7 +480,7 @@ local function register_entity(entity_id, mesh, textures, drop, on_rightclick, o
 		end
 
 		-- Give achievement when player reached a distance of 1000 nodes from the start position
-		if self._driver and (vector.distance(self._start_pos, pos) >= 1000) then
+		if self._driver and self._driver:is_player() and (vector.distance(self._start_pos, pos) >= 1000) then
 			awards.unlock(self._driver, "mcl:onARail")
 		end
 
@@ -634,7 +668,7 @@ register_minecart(
 		if self._driver and player_name == self._driver then
 			detach_driver(self)
 		elseif not self._driver then
-			self._driver = player_name
+			self._driver = clicker
 			self._start_pos = self.object:get_pos()
 			mcl_player.player_attached[player_name] = true
 			clicker:set_attach(self.object, "", {x=0, y=-1.75, z=-2}, {x=0, y=0, z=0})