4 files changed, 26 insertions, 2 deletions
diff --git a/src/ai/api/ai_changelog.hpp b/src/ai/api/ai_changelog.hpp
index 03ba5dca4..b767778d9 100644
--- a/src/ai/api/ai_changelog.hpp
+++ b/src/ai/api/ai_changelog.hpp
@@ -24,6 +24,7 @@
  * \li AIIndustry::GetIndustryID
  * \li AIIndustryType::INDUSTRYTYPE_TOWN
  * \li AIIndustryType::INDUSTRYTYPE_UNKNOWN
+ * \li AIOrder::IsVoidOrder
  *
  * API removals:
  * \li HasNext for all lists.
@@ -34,6 +35,7 @@
  * \li AIEngine::GetPower can be used for road vehicles.
  * \li AIEngine::GetWeight can be used for road vehicles.
  * \li AIEngine::GetMaxTractiveEffort can be used for road vehicles.
+ * \li AIOrder::GetOrderFlags returns AIOrder::AIOF_INVALID for void orders as well.
  *
  * \b 1.0.3
  *
diff --git a/src/ai/api/ai_order.cpp b/src/ai/api/ai_order.cpp
index bf55cc504..370cff4f6 100644
--- a/src/ai/api/ai_order.cpp
+++ b/src/ai/api/ai_order.cpp
@@ -99,6 +99,15 @@ static const Order *ResolveOrder(VehicleID vehicle_id, AIOrder::OrderPosition or
 	return order->GetType() == OT_CONDITIONAL;
 }
 
+/* static */ bool AIOrder::IsVoidOrder(VehicleID vehicle_id, OrderPosition order_position)
+{
+	if (order_position == ORDER_CURRENT) return false;
+	if (!IsValidVehicleOrder(vehicle_id, order_position)) return false;
+
+	const Order *order = Vehicle::Get(vehicle_id)->GetOrder(order_position);
+	return order->GetType() == OT_DUMMY;
+}
+
 /* static */ bool AIOrder::IsCurrentOrderPartOfOrderList(VehicleID vehicle_id)
 {
 	if (AIVehicle::IsValidVehicle(vehicle_id)) return false;
@@ -224,7 +233,7 @@ static const Order *ResolveOrder(VehicleID vehicle_id, AIOrder::OrderPosition or
 	if (!IsValidVehicleOrder(vehicle_id, order_position)) return AIOF_INVALID;
 
 	const Order *order = ::ResolveOrder(vehicle_id, order_position);
-	if (order == NULL || order->GetType() == OT_CONDITIONAL) return AIOF_INVALID;
+	if (order == NULL || order->GetType() == OT_CONDITIONAL || order->GetType() == OT_DUMMY) return AIOF_INVALID;
 
 	AIOrderFlags order_flags = AIOF_NONE;
 	order_flags |= (AIOrderFlags)order->GetNonStopType();
diff --git a/src/ai/api/ai_order.hpp b/src/ai/api/ai_order.hpp
index 4bdd3f560..8f142f3a6 100644
--- a/src/ai/api/ai_order.hpp
+++ b/src/ai/api/ai_order.hpp
@@ -173,6 +173,18 @@ public:
 	static bool IsConditionalOrder(VehicleID vehicle_id, OrderPosition order_position);
 
 	/**
+	 * Checks whether the given order is a void order.
+	 * A void order is an order that used to be a goto station, depot or waypoint order but
+	 * its destination got removed. In OpenTTD these orders as shown as "(Invalid Order)"
+	 * in the order list of a vehicle.
+	 * @param vehicle_id The vehicle to check.
+	 * @param order_position The order index to check.
+	 * @pre order_position != ORDER_CURRENT && IsValidVehicleOrder(vehicle_id, order_position).
+	 * @return True if and only if the order is a void order.
+	 */
+	static bool IsVoidOrder(VehicleID vehicle_id, OrderPosition order_position);
+
+	/**
 	 * Checks whether the current order is part of the orderlist.
 	 * @param vehicle_id The vehicle to check.
 	 * @pre AIVehicle::IsValidVehicle(vehicle_id).
@@ -240,7 +252,7 @@ public:
 	 * @param vehicle_id The vehicle to get the destination for.
 	 * @param order_position The order to get the destination for.
 	 * @pre IsValidVehicleOrder(vehicle_id, order_position).
-	 * @pre order_position == ORDER_CURRENT || !IsConditionalOrder(vehicle_id, order_position).
+	 * @pre order_position == ORDER_CURRENT || (!IsConditionalOrder(vehicle_id, order_position) && !IsVoidOrder(vehicle_id, order_position)).
 	 * @note Giving ORDER_CURRENT as order_position will give the order that is
 	 *  currently being executed by the vehicle. This is not necessarily the
 	 *  current order as given by ResolveOrderPosition (the current index in the
diff --git a/src/ai/api/ai_order.hpp.sq b/src/ai/api/ai_order.hpp.sq
index d79964e00..dff9d889f 100644
--- a/src/ai/api/ai_order.hpp.sq
+++ b/src/ai/api/ai_order.hpp.sq
@@ -94,6 +94,7 @@ void SQAIOrder_Register(Squirrel *engine)
 	SQAIOrder.DefSQStaticMethod(engine, &AIOrder::IsGotoDepotOrder,              "IsGotoDepotOrder",              3, ".ii");
 	SQAIOrder.DefSQStaticMethod(engine, &AIOrder::IsGotoWaypointOrder,           "IsGotoWaypointOrder",           3, ".ii");
 	SQAIOrder.DefSQStaticMethod(engine, &AIOrder::IsConditionalOrder,            "IsConditionalOrder",            3, ".ii");
+	SQAIOrder.DefSQStaticMethod(engine, &AIOrder::IsVoidOrder,                   "IsVoidOrder",                   3, ".ii");
 	SQAIOrder.DefSQStaticMethod(engine, &AIOrder::IsCurrentOrderPartOfOrderList, "IsCurrentOrderPartOfOrderList", 2, ".i");
 	SQAIOrder.DefSQStaticMethod(engine, &AIOrder::ResolveOrderPosition,          "ResolveOrderPosition",          3, ".ii");
 	SQAIOrder.DefSQStaticMethod(engine, &AIOrder::AreOrderFlagsValid,            "AreOrderFlagsValid",            3, ".ii");