Fix: Trivial autoreplace of mixed cargo articulated engines (#11253)

Do not fail autoreplace/autorenew of mixed cargo articulated engines
due to an inability to refit to mixed cargoes, when no refit is
required because the target engine already has a suitable set of cargoes.
Notably, this allows autorenew (autoreplace to same engine type)
to succeed.

src/articulated_vehicles.cpp

@@ -8,6 +8,7 @@
 /** @file articulated_vehicles.cpp Implementation of articulated vehicles. */
 
 #include "stdafx.h"
+#include "core/bitmath_func.hpp"
 #include "core/random_func.hpp"
 #include "train.h"
 #include "roadveh.h"
@@ -161,6 +162,35 @@ CargoArray GetCapacityOfArticulatedParts(EngineID engine)
 	return capacity;
 }
 
+/**
+ * Get the cargo mask of the parts of a given engine.
+ * @param engine The engine to get the capacities from.
+ * @return The cargo mask.
+ */
+CargoTypes GetCargoTypesOfArticulatedParts(EngineID engine)
+{
+	CargoTypes cargoes = 0;
+	const Engine *e = Engine::Get(engine);
+
+	CargoID cargo_type;
+	uint16_t cargo_capacity = GetVehicleDefaultCapacity(engine, &cargo_type);
+	if (cargo_type < NUM_CARGO && cargo_capacity > 0) SetBit(cargoes, cargo_type);
+
+	if (!e->IsGroundVehicle()) return cargoes;
+
+	if (!HasBit(e->info.callback_mask, CBM_VEHICLE_ARTIC_ENGINE)) return cargoes;
+
+	for (uint i = 1; i < MAX_ARTICULATED_PARTS; i++) {
+		EngineID artic_engine = GetNextArticulatedPart(i, engine);
+		if (artic_engine == INVALID_ENGINE) break;
+
+		cargo_capacity = GetVehicleDefaultCapacity(artic_engine, &cargo_type);
+		if (cargo_type < NUM_CARGO && cargo_capacity > 0) SetBit(cargoes, cargo_type);
+	}
+
+	return cargoes;
+}
+
 /**
  * Checks whether any of the articulated parts is refittable
  * @param engine the first part
@@ -226,22 +256,26 @@ CargoTypes GetUnionOfArticulatedRefitMasks(EngineID engine, bool include_initial
 }
 
 /**
- * Tests if all parts of an articulated vehicle are refitted to the same cargo.
+ * Get cargo mask of all cargoes carried by an articulated vehicle.
  * Note: Vehicles not carrying anything are ignored
  * @param v the first vehicle in the chain
  * @param cargo_type returns the common CargoID if needed. (CT_INVALID if no part is carrying something or they are carrying different things)
- * @return true if some parts are carrying different cargoes, false if all parts are carrying the same (nothing is also the same)
+ * @return cargo mask, may be 0 if the no vehicle parts have cargo capacity
  */
-bool IsArticulatedVehicleCarryingDifferentCargoes(const Vehicle *v, CargoID *cargo_type)
+CargoTypes GetCargoTypesOfArticulatedVehicle(const Vehicle *v, CargoID *cargo_type)
 {
+	CargoTypes cargoes = 0;
 	CargoID first_cargo = CT_INVALID;
 
 	do {
 		if (IsValidCargoID(v->cargo_type) && v->GetEngine()->CanCarryCargo()) {
+			SetBit(cargoes, v->cargo_type);
 			if (!IsValidCargoID(first_cargo)) first_cargo = v->cargo_type;
 			if (first_cargo != v->cargo_type) {
-				if (cargo_type != nullptr) *cargo_type = CT_INVALID;
-				return true;
+				if (cargo_type != nullptr) {
+					*cargo_type = CT_INVALID;
+					cargo_type = nullptr;
+				}
 			}
 		}
 
@@ -249,7 +283,7 @@ bool IsArticulatedVehicleCarryingDifferentCargoes(const Vehicle *v, CargoID *car
 	} while (v != nullptr);
 
 	if (cargo_type != nullptr) *cargo_type = first_cargo;
-	return false;
+	return cargoes;
 }
 
 /**

src/articulated_vehicles.h

@@ -15,10 +15,11 @@
 
 uint CountArticulatedParts(EngineID engine_type, bool purchase_window);
 CargoArray GetCapacityOfArticulatedParts(EngineID engine);
+CargoTypes GetCargoTypesOfArticulatedParts(EngineID engine);
 void AddArticulatedParts(Vehicle *first);
 void GetArticulatedRefitMasks(EngineID engine, bool include_initial_cargo_type, CargoTypes *union_mask, CargoTypes *intersection_mask);
 CargoTypes GetUnionOfArticulatedRefitMasks(EngineID engine, bool include_initial_cargo_type);
-bool IsArticulatedVehicleCarryingDifferentCargoes(const Vehicle *v, CargoID *cargo_type);
+CargoTypes GetCargoTypesOfArticulatedVehicle(const Vehicle *v, CargoID *cargo_type);
 bool IsArticulatedVehicleRefittable(EngineID engine);
 bool IsArticulatedEngine(EngineID engine_type);
 void CheckConsistencyOfArticulatedVehicle(const Vehicle *v);

src/autoreplace_cmd.cpp

@@ -16,6 +16,7 @@
 #include "autoreplace_func.h"
 #include "autoreplace_gui.h"
 #include "articulated_vehicles.h"
+#include "core/bitmath_func.hpp"
 #include "core/random_func.hpp"
 #include "vehiclelist.h"
 #include "road.h"
@@ -236,7 +237,15 @@ static CargoID GetNewCargoTypeForReplace(Vehicle *v, EngineID engine_type, bool
 	if (union_mask == 0) return CT_NO_REFIT; // Don't try to refit an engine with no cargo capacity
 
 	CargoID cargo_type;
-	if (IsArticulatedVehicleCarryingDifferentCargoes(v, &cargo_type)) return CT_INVALID; // We cannot refit to mixed cargoes in an automated way
+	CargoTypes cargo_mask = GetCargoTypesOfArticulatedVehicle(v, &cargo_type);
+	if (!HasAtMostOneBit(cargo_mask)) {
+		CargoTypes new_engine_default_cargoes = GetCargoTypesOfArticulatedParts(engine_type);
+		if ((cargo_mask & new_engine_default_cargoes) == cargo_mask) {
+			return CT_NO_REFIT; // engine_type is already a mixed cargo type which matches the incoming vehicle by default, no refit required
+		}
+
+		return CT_INVALID; // We cannot refit to mixed cargoes in an automated way
+	}
 
 	if (!IsValidCargoID(cargo_type)) {
 		if (v->type != VEH_TRAIN) return CT_NO_REFIT; // If the vehicle does not carry anything at all, every replacement is fine.

src/vehicle.cpp

@@ -229,13 +229,20 @@ bool Vehicle::NeedsServicing() const
 		/* Is there anything to refit? */
 		if (union_mask != 0) {
 			CargoID cargo_type;
-			/* We cannot refit to mixed cargoes in an automated way */
-			if (IsArticulatedVehicleCarryingDifferentCargoes(v, &cargo_type)) continue;
-
-			/* Did the old vehicle carry anything? */
-			if (IsValidCargoID(cargo_type)) {
-				/* We can't refit the vehicle to carry the cargo we want */
-				if (!HasBit(available_cargo_types, cargo_type)) continue;
+			CargoTypes cargo_mask = GetCargoTypesOfArticulatedVehicle(v, &cargo_type);
+			if (!HasAtMostOneBit(cargo_mask)) {
+				CargoTypes new_engine_default_cargoes = GetCargoTypesOfArticulatedParts(new_engine);
+				if ((cargo_mask & new_engine_default_cargoes) != cargo_mask) {
+					/* We cannot refit to mixed cargoes in an automated way */
+					continue;
+				}
+				/* engine_type is already a mixed cargo type which matches the incoming vehicle by default, no refit required */
+			} else {
+				/* Did the old vehicle carry anything? */
+				if (IsValidCargoID(cargo_type)) {
+					/* We can't refit the vehicle to carry the cargo we want */
+					if (!HasBit(available_cargo_types, cargo_type)) continue;
+				}
 			}
 		}