Only run step collapsing based on original waypoints parameter (#4829)

src/engine/plugins/match.cpp

@@ -247,6 +247,7 @@ Status MatchPlugin::HandleRequest(const RoutingAlgorithmsInterface &algorithms,
     }
 
     // Error: Check if user-supplied waypoints can be found in the resulting matches
+    if (!parameters.waypoints.empty())
     {
         std::set<std::size_t> tidied_waypoints(tidied.parameters.waypoints.begin(),
                                                tidied.parameters.waypoints.end());
@@ -262,6 +263,9 @@ Status MatchPlugin::HandleRequest(const RoutingAlgorithmsInterface &algorithms,
                 "NoMatch", "Requested waypoint parameter could not be matched.", json_result);
         }
     }
+    // we haven't errored yet, only allow leg collapsing if it was originally requested
+    BOOST_ASSERT(parameters.waypoints.empty() || sub_matchings.size() == 1);
+    const auto collapse_legs = !parameters.waypoints.empty();
 
     // each sub_route will correspond to a MatchObject
     std::vector<InternalRouteResult> sub_routes(sub_matchings.size());
@@ -286,7 +290,7 @@ Status MatchPlugin::HandleRequest(const RoutingAlgorithmsInterface &algorithms,
         sub_routes[index] =
             algorithms.ShortestPathSearch(sub_routes[index].segment_end_coordinates, {false});
         BOOST_ASSERT(sub_routes[index].shortest_path_weight != INVALID_EDGE_WEIGHT);
-        if (!tidied.parameters.waypoints.empty())
+        if (collapse_legs)
         {
             std::vector<bool> waypoint_legs;
             waypoint_legs.reserve(sub_matchings[index].indices.size());