Fix OpenTTD#7670: Cache the origin tile to prevent recurring calls to…

… the road pathfinder when a vehicle is blocked by another

src/pathfinder/yapf/yapf_road.cpp

@@ -402,6 +402,8 @@ class CYapfFollowRoadT
 			Node &best_next_node = *pNode;
 			assert(best_next_node.GetTile() == tile);
 			next_trackdir = best_next_node.GetTrackdir();
+			path_cache.origin_td = next_trackdir;
+			path_cache.origin_tile = tile;
 			/* remove last element for the special case when tile == dest_tile */
 			if (path_found && !path_cache.empty() && tile == v->dest_tile) {
 				path_cache.td.pop_back();

src/roadveh.h

@@ -83,6 +83,8 @@ void RoadVehUpdateCache(RoadVehicle *v, bool same_length = false);
 void GetRoadVehSpriteSize(EngineID engine, uint &width, uint &height, int &xoffs, int &yoffs, EngineImageType image_type);
 
 struct RoadVehPathCache {
+	Trackdir origin_td = INVALID_TRACKDIR;
+	TileIndex origin_tile = INVALID_TILE;
 	std::deque<Trackdir> td;
 	std::deque<TileIndex> tile;
 
@@ -96,6 +98,8 @@ struct RoadVehPathCache {
 
 	inline void clear()
 	{
+		this->origin_td = INVALID_TRACKDIR;
+		this->origin_tile = INVALID_TILE;
 		this->td.clear();
 		this->tile.clear();
 	}

src/roadveh_cmd.cpp

@@ -968,6 +968,9 @@ static Trackdir RoadFindPathToDest(RoadVehicle *v, TileIndex tile, DiagDirection
 	/* Attempt to follow cached path. */
 	if (!v->path.empty()) {
 		if (v->path.tile.front() != tile) {
+			if (IsValidTile(v->path.origin_tile) && v->path.origin_tile == tile && HasBit(trackdirs, v->path.origin_td)) {
+				return_track(v->path.origin_td);
+			}
 			/* Vehicle didn't expect a choice here, invalidate its path. */
 			v->path.clear();
 		} else {
@@ -977,6 +980,8 @@ static Trackdir RoadFindPathToDest(RoadVehicle *v, TileIndex tile, DiagDirection
 				v->path.td.pop_front();
 				v->path.tile.pop_front();
 				return_track(trackdir);
+			} else if (IsValidTile(v->path.origin_tile) && v->path.origin_tile == tile && HasBit(trackdirs, v->path.origin_td)) {
+				return_track(v->path.origin_td);
 			}
 
 			/* Vehicle expected a choice which is no longer available. */