ignore invalid only_* restrictions

CHANGELOG.md

@@ -10,6 +10,7 @@
       - Reduced semantic of merge to refer only to merges from a lane onto a motorway-like road
     - Bugfixes
       - Fixed an issue that would result in segfaults for viaroutes with an invalid intermediate segment when u-turns were allowed at the via-location
+      - Invalid only_* restrictions could result in loss of connectivity. As a fallback, we assume all turns allowed when the restriction is not valid
 
 # 5.3.0
   Changes from 5.3.0-rc.3

features/car/restrictions.feature

@@ -149,11 +149,27 @@ Feature: Car - Turn restrictions
             | type        | way:from | way:to | node:via | restriction    |
             | restriction | sj       | wj     | j        | only_left_turn |
 
+    Scenario: Car - Only right turn, invalid
+        Given the node map
+            |   | n |   |   |
+            | w | j | e | r |
+            |   | s |   |   |
+
+        And the ways
+            | nodes | oneway |
+            | sj    | yes    |
+            | nj    | -1     |
+            | wj    | -1     |
+            | ej    | -1     |
+            | re    | -1     |
+
+        And the relations
+            | type        | way:from | way:to | node:via | restriction   |
+            | restriction | sj       | er     | j        | only_right_on |
+
         When I route I should get
-            | from | to | route    |
-            | s    | w  | sj,wj,wj |
-            | s    | n  |          |
-            | s    | e  |          |
+            | from | to | route       |
+            | s    | r  | sj,ej,re,re |
 
     @only_turning
     Scenario: Car - Only right turn

src/extractor/guidance/intersection_generator.cpp

@@ -55,8 +55,21 @@ Intersection IntersectionGenerator::GetConnectedRoads(const NodeID from_node,
 {
     Intersection intersection;
     const NodeID turn_node = node_based_graph.GetTarget(via_eid);
-    const NodeID only_restriction_to_node =
-        restriction_map.CheckForEmanatingIsOnlyTurn(from_node, turn_node);
+    const NodeID only_restriction_to_node = [&]() {
+        // If only restrictions refer to invalid ways somewhere far away, we rather ignore the
+        // restriction than to not route over the intersection at all.
+        const auto only_restriction_to_node =
+            restriction_map.CheckForEmanatingIsOnlyTurn(from_node, turn_node);
+        if (only_restriction_to_node != SPECIAL_NODEID)
+        {
+            // check if we can find an edge in the edge-rage
+            for (const auto onto_edge : node_based_graph.GetAdjacentEdgeRange(turn_node))
+                if (only_restriction_to_node == node_based_graph.GetTarget(onto_edge))
+                    return only_restriction_to_node;
+        }
+        // Ignore broken only restrictions.
+        return SPECIAL_NODEID;
+    }();
     const bool is_barrier_node = barrier_nodes.find(turn_node) != barrier_nodes.end();
 
     bool has_uturn_edge = false;

src/extractor/restriction_map.cpp

@@ -143,11 +143,9 @@ bool RestrictionMap::CheckIfTurnIsRestricted(const NodeID node_u,
         {
             return true;
         }
-        if (node_w != restriction_target.target_node && // target not found
-            restriction_target.is_only)                 // and is an only restriction
-        {
-            return true;
-        }
+        // We could be tempted to check for `only` restrictions here as well. However, that check is
+        // actually perfomed in intersection generation where we can also verify if the only
+        // restriction is valid at all.
     }
     return false;
 }