Fix crash when route starts/ends at manoeuvre relation via node (#7339)

* Fix assertion failure in collapseSegregatedTurnInstructions

* Add test for routes starting/ending at manoeuvre=fork via node

* Skip manoeuvre overrides on depart/arrive waypoint steps

* Improve the log

* Fix the format

Author: afarber

CHANGELOG.md

@@ -1,5 +1,7 @@
 # Unreleased
   - Changes from 6.0.0
+    - Routing:
+      - FIXED: Crash when route starts or ends at `type=manoeuvre` relation via node [#7287](https://github.com/Project-OSRM/osrm-backend/issues/7287)
     - Profiles:
       - ADDED: Add exception for audible fences (`barrier=fence` with `sensory=audible` or `sensory=audio`) that deter livestock but do not block vehicles [#6964](https://github.com/Project-OSRM/osrm-backend/issues/6964)
       - ADDED: Use `is_sidepath:of:name` and `street:name` as fallback names for unnamed sidewalks and sidepaths in foot and bicycle profiles [#7259](https://github.com/Project-OSRM/osrm-backend/issues/7259)

features/guidance/collapse-detail.feature

@@ -176,3 +176,63 @@ Feature: Collapse
         When I route I should get
             | waypoints | route   | turns                               |
             | c,e       | road,,, | depart,turn right,turn right,arrive |
+
+    # Route starting at via node of manoeuvre=fork relation
+    @manoeuvre-fork
+    Scenario: Route starting at fork node with manoeuvre relation
+        Given the node map
+            """
+                    c
+                   /
+            a-----b
+                   \
+                    d-----e
+            """
+
+        And the ways
+            | nodes | highway  | name   | oneway |
+            | ab    | motorway | main   | yes    |
+            | bc    | motorway | left   | yes    |
+            | bd    | motorway | right  | yes    |
+            | de    | motorway | right  | yes    |
+
+        And the relations
+            | type      | way:from | node:via | way:to | manoeuvre | direction    |
+            | manoeuvre | ab       | b        | bc     | fork      | slight_left  |
+            | manoeuvre | ab       | b        | bd     | fork      | slight_right |
+
+        When I route I should get
+            | waypoints | route             | turns                            |
+            | a,c       | main,left,left    | depart,fork slight left,arrive   |
+            | a,e       | main,right,right  | depart,fork slight right,arrive  |
+            # Depart from fork via node - no fork instruction needed
+            | b,c       | left,left         | depart,arrive                    |
+            | b,e       | right,right       | depart,arrive                    |
+
+    # Route ending at via node of manoeuvre=fork relation
+    @manoeuvre-fork
+    Scenario: Route ending at fork node with manoeuvre relation
+        Given the node map
+            """
+                    c
+                   /
+            a-----b
+                   \
+                    d-----e
+            """
+
+        And the ways
+            | nodes | highway  | name   | oneway |
+            | ab    | motorway | main   | yes    |
+            | bc    | motorway | left   | yes    |
+            | bd    | motorway | right  | yes    |
+            | de    | motorway | right  | yes    |
+
+        And the relations
+            | type      | way:from | node:via | way:to | manoeuvre | direction    |
+            | manoeuvre | ab       | b        | bc     | fork      | slight_left  |
+            | manoeuvre | ab       | b        | bd     | fork      | slight_right |
+
+        When I route I should get
+            | waypoints | route       | turns         |
+            | a,b       | main,main   | depart,arrive |

src/engine/guidance/collapse_turns.cpp

@@ -591,6 +591,13 @@ void suppressStep(RouteStep &step_at_turn_location, RouteStep &step_after_turn_l
 [[nodiscard]] RouteSteps collapseSegregatedTurnInstructions(RouteSteps steps)
 {
     // make sure we can safely iterate over all steps (has depart/arrive with TurnType::NoTurn)
+    // Return early if preconditions aren't met (can happen with certain manoeuvre relations)
+    if (hasTurnType(steps.front()) || hasTurnType(steps.back()))
+        return steps;
+
+    if (!hasWaypointType(steps.front()) || !hasWaypointType(steps.back()))
+        return steps;
+
     BOOST_ASSERT(!hasTurnType(steps.front()) && !hasTurnType(steps.back()));
     BOOST_ASSERT(hasWaypointType(steps.front()) && hasWaypointType(steps.back()));
 

src/engine/guidance/post_processing.cpp

@@ -679,7 +679,14 @@ void applyOverrides(const datafacade::BaseDataFacade &facade,
                 // in its geometry
                 if (step_to_update != route_iter)
                 {
-                    // Don't update the last step (it's an arrive instruction)
+                    // Manoeuvre overrides apply to driving maneuvers, not waypoint steps.
+                    // Depart/arrive steps mark route endpoints and should keep NoTurn type.
+                    if (hasWaypointType(*step_to_update))
+                    {
+                        util::Log(logDEBUG)
+                            << "Skipping maneuver override on waypoint step" << std::endl;
+                        continue;
+                    }
                     util::Log(logDEBUG) << "Updating step "
                                         << std::distance(steps.begin(), steps.end()) -
                                                std::distance(step_to_update, steps.end())