# HG changeset patch
# User Koen Bussemaker <koen_bussemaker@hotmail.com>
# Date 2023-06-30 19:17:26
# Node ID 9ef479faae5f115e3311550543575b365d95a4c0
# Parent  a14b989855d2fa4f8400d962f36032ea6adade49

Change: Autorail / autoroad tools can start dragging from invalid tiles

diff --git a/src/rail_cmd.cpp b/src/rail_cmd.cpp
--- a/src/rail_cmd.cpp
+++ b/src/rail_cmd.cpp
@@ -875,8 +875,8 @@ static CommandCost ValidateAutoDrag(Trac
  * @param railtype railroad type normal/maglev (0 = normal, 1 = mono, 2 = maglev), only used for building
  * @param track track-orientation
  * @param remove remove tracks?
- * @param auto_remove_signals false = build up to an obstacle, true = fail if an obstacle is found (used for AIs), only used for building
- * @param fail_on_obstacle false = error on signal in the way, true = auto remove signals when in the way, only used for building
+ * @param auto_remove_signals false = error on signal in the way, true = auto remove signals when in the way, only used for building
+ * @param fail_on_obstacle false = build starting from and up to an obstacle, true = fail if an obstacle is found (used for AIs)
  * @return the cost of this operation or an error
  */
 static CommandCost CmdRailTrackHelper(DoCommandFlag flags, TileIndex tile, TileIndex end_tile, RailType railtype, Track track, bool remove, bool auto_remove_signals, bool fail_on_obstacle)
@@ -900,7 +900,7 @@ static CommandCost CmdRailTrackHelper(Do
 			last_error = ret;
 			if (last_error.GetErrorMessage() != STR_ERROR_ALREADY_BUILT && !remove) {
 				if (fail_on_obstacle) return last_error;
-				break;
+				if (had_success) break; // Keep going if we haven't constructed any rail yet, skipping the start of the drag
 			}
 
 			/* Ownership errors are more important. */
diff --git a/src/road_cmd.cpp b/src/road_cmd.cpp
--- a/src/road_cmd.cpp
+++ b/src/road_cmd.cpp
@@ -1034,7 +1034,7 @@ CommandCost CmdBuildLongRoad(DoCommandFl
 			last_error = ret;
 			if (last_error.GetErrorMessage() != STR_ERROR_ALREADY_BUILT) {
 				if (is_ai) return last_error;
-				break;
+				if (had_success) break; // Keep going if we haven't constructed any road yet, skipping the start of the drag
 			}
 		} else {
 			had_success = true;