Start a pathfinding v2 API. #555 (#596)

The v1 path that all callers need is available by transforming PathV2 to
v1. The plan is to now gradually change callers to natively use PathV2
instead.

map_model/src/connectivity/mod.rs

@@ -106,7 +106,8 @@ pub fn debug_vehicle_costs(
         return None;
     }
 
-    let (_, cost) = crate::pathfind::dijkstra::pathfind(req.clone(), map.routing_params(), map)?;
+    let cost =
+        crate::pathfind::dijkstra::pathfind(req.clone(), map.routing_params(), map)?.get_cost();
 
     let graph = build_graph_for_vehicles(map, req.constraints);
     let road_costs = petgraph::algo::dijkstra(

map_model/src/lib.rs

@@ -56,7 +56,9 @@ pub use crate::objects::turn::{
 pub use crate::objects::zone::{AccessRestrictions, Zone};
 pub use crate::pathfind::uber_turns::{IntersectionCluster, UberTurn};
 use crate::pathfind::Pathfinder;
-pub use crate::pathfind::{Path, PathConstraints, PathRequest, PathStep, RoutingParams};
+pub use crate::pathfind::{
+    Path, PathConstraints, PathRequest, PathStep, PathStepV2, PathV2, RoutingParams,
+};
 pub use crate::traversable::{Position, Traversable, MAX_BIKE_SPEED, MAX_WALKING_SPEED};
 
 mod city;

map_model/src/map.rs

@@ -579,23 +579,28 @@ impl Map {
 
     pub fn pathfind(&self, req: PathRequest) -> Result<Path> {
         assert!(!self.pathfinder_dirty);
-        self.pathfinder
+        let path = self
+            .pathfinder
             .pathfind(req.clone(), self)
-            .ok_or_else(|| anyhow!("can't fulfill {}", req))
+            .ok_or_else(|| anyhow!("can't fulfill {}", req))?;
+        path.to_v1(self)
     }
     pub fn pathfind_avoiding_roads(
         &self,
         req: PathRequest,
         avoid: BTreeSet<RoadID>,
-    ) -> Option<Path> {
+    ) -> Result<Path> {
         assert!(!self.pathfinder_dirty);
-        self.pathfinder.pathfind_avoiding_roads(req, avoid, self)
+        let path = self.pathfinder.pathfind_avoiding_roads(req, avoid, self)?;
+        path.to_v1(self)
     }
     pub fn pathfind_with_params(&self, req: PathRequest, params: &RoutingParams) -> Result<Path> {
         assert!(!self.pathfinder_dirty);
-        self.pathfinder
+        let path = self
+            .pathfinder
             .pathfind_with_params(req.clone(), params, self)
-            .ok_or_else(|| anyhow!("can't fulfill {}", req))
+            .ok_or_else(|| anyhow!("can't fulfill {}", req))?;
+        path.to_v1(self)
     }
 
     pub fn should_use_transit(

map_model/src/pathfind/ch.rs

@@ -9,7 +9,7 @@ use geom::Duration;
 use crate::pathfind::dijkstra;
 use crate::pathfind::vehicles::VehiclePathfinder;
 use crate::pathfind::walking::SidewalkPathfinder;
-use crate::{BusRouteID, BusStopID, Map, Path, PathConstraints, PathRequest, Position};
+use crate::{BusRouteID, BusStopID, Map, PathConstraints, PathRequest, PathV2, Position};
 
 #[derive(Serialize, Deserialize)]
 pub struct ContractionHierarchyPathfinder {
@@ -53,8 +53,8 @@ impl ContractionHierarchyPathfinder {
         }
     }
 
-    pub fn pathfind(&self, req: PathRequest, map: &Map) -> Option<Path> {
-        (match req.constraints {
+    pub fn pathfind(&self, req: PathRequest, map: &Map) -> Option<PathV2> {
+        match req.constraints {
             PathConstraints::Pedestrian => self.walking_graph.pathfind(req, map),
             PathConstraints::Car => self.car_graph.pathfind(req, map),
             PathConstraints::Bike => self.bike_graph.pathfind(req, map),
@@ -62,8 +62,7 @@ impl ContractionHierarchyPathfinder {
             // Light rail networks are absolutely tiny; using a contraction hierarchy for them is
             // overkill. And in fact, it costs a bit of memory and file size, so don't do it!
             PathConstraints::Train => dijkstra::pathfind(req, map.routing_params(), map),
-        })
-        .map(|(path, _)| path)
+        }
     }
 
     pub fn should_use_transit(

map_model/src/pathfind/dijkstra.rs

@@ -2,21 +2,21 @@
 
 use std::collections::BTreeSet;
 
+use anyhow::Result;
 use petgraph::graphmap::DiGraphMap;
 
 use geom::Duration;
 
-use crate::pathfind::v2::path_v2_to_v1;
 use crate::pathfind::walking::{one_step_walking_path, walking_path_to_steps, WalkingNode};
 use crate::pathfind::{vehicle_cost, zone_cost};
 use crate::{
-    DirectedRoadID, Map, MovementID, Path, PathConstraints, PathRequest, RoadID, RoutingParams,
+    DirectedRoadID, Map, MovementID, PathConstraints, PathRequest, PathV2, RoadID, RoutingParams,
     Traversable,
 };
 
 // TODO These should maybe keep the DiGraphMaps as state. It's cheap to recalculate it for edits.
 
-pub fn pathfind(req: PathRequest, params: &RoutingParams, map: &Map) -> Option<(Path, Duration)> {
+pub fn pathfind(req: PathRequest, params: &RoutingParams, map: &Map) -> Option<PathV2> {
     if req.constraints == PathConstraints::Pedestrian {
         pathfind_walking(req, map)
     } else {
@@ -42,7 +42,7 @@ pub fn pathfind_avoiding_roads(
     req: PathRequest,
     avoid: BTreeSet<RoadID>,
     map: &Map,
-) -> Option<(Path, Duration)> {
+) -> Result<PathV2> {
     assert_eq!(req.constraints, PathConstraints::Car);
     let mut graph = DiGraphMap::new();
     for dr in map.all_directed_roads_for(req.constraints) {
@@ -54,7 +54,8 @@ pub fn pathfind_avoiding_roads(
         }
     }
 
-    calc_path(graph, req, map.routing_params(), map)
+    calc_path(graph, req.clone(), map.routing_params(), map)
+        .ok_or_else(|| anyhow!("No path for {} avoiding {} roads", req, avoid.len()))
 }
 
 fn calc_path(
@@ -62,9 +63,9 @@ fn calc_path(
     req: PathRequest,
     params: &RoutingParams,
     map: &Map,
-) -> Option<(Path, Duration)> {
+) -> Option<PathV2> {
     let end = map.get_l(req.end.lane()).get_directed_parent();
-    let (cost, path) = petgraph::algo::astar(
+    let (cost, steps) = petgraph::algo::astar(
         &graph,
         map.get_l(req.start.lane()).get_directed_parent(),
         |dr| dr == end,
@@ -74,10 +75,8 @@ fn calc_path(
         },
         |_| Duration::ZERO,
     )?;
-
     // TODO No uber-turns yet
-    let path = path_v2_to_v1(req, path, Vec::new(), map).ok()?;
-    Some((path, cost))
+    Some(PathV2::from_roads(steps, req, cost, Vec::new(), map))
 }
 
 pub fn build_graph_for_pedestrians(map: &Map) -> DiGraphMap<WalkingNode, Duration> {
@@ -120,7 +119,7 @@ pub fn build_graph_for_pedestrians(map: &Map) -> DiGraphMap<WalkingNode, Duratio
     graph
 }
 
-fn pathfind_walking(req: PathRequest, map: &Map) -> Option<(Path, Duration)> {
+fn pathfind_walking(req: PathRequest, map: &Map) -> Option<PathV2> {
     if req.start.lane() == req.end.lane() {
         return Some(one_step_walking_path(req, map));
     }
@@ -137,5 +136,5 @@ fn pathfind_walking(req: PathRequest, map: &Map) -> Option<(Path, Duration)> {
         |_| Duration::ZERO,
     )?;
     let steps = walking_path_to_steps(nodes, map);
-    Some((Path::new(map, steps, req, Vec::new()), cost))
+    Some(PathV2::new(steps, req, cost, Vec::new()))
 }

map_model/src/pathfind/mod.rs

@@ -9,6 +9,7 @@ pub use self::ch::ContractionHierarchyPathfinder;
 pub use self::dijkstra::{build_graph_for_pedestrians, build_graph_for_vehicles};
 pub use self::pathfinder::Pathfinder;
 pub use self::v1::{Path, PathRequest, PathStep};
+pub use self::v2::{PathStepV2, PathV2};
 pub use self::vehicles::vehicle_cost;
 pub use self::walking::WalkingNode;
 use crate::{osm, Lane, LaneID, LaneType, Map, MovementID};

map_model/src/pathfind/pathfinder.rs

@@ -1,12 +1,13 @@
 use std::collections::BTreeSet;
 
+use anyhow::Result;
 use serde::{Deserialize, Serialize};
 
 use abstutil::Timer;
 
 use crate::pathfind::ch::ContractionHierarchyPathfinder;
 use crate::pathfind::dijkstra;
-use crate::{BusRouteID, BusStopID, Map, Path, PathRequest, Position, RoadID, RoutingParams};
+use crate::{BusRouteID, BusStopID, Map, PathRequest, PathV2, Position, RoadID, RoutingParams};
 
 /// Most of the time, prefer using the faster contraction hierarchies. But sometimes, callers can
 /// explicitly opt into a slower (but preparation-free) pathfinder that just uses Dijkstra's
@@ -19,7 +20,7 @@ pub enum Pathfinder {
 
 impl Pathfinder {
     /// Finds a path from a start to an end for a certain type of agent.
-    pub fn pathfind(&self, req: PathRequest, map: &Map) -> Option<Path> {
+    pub fn pathfind(&self, req: PathRequest, map: &Map) -> Option<PathV2> {
         self.pathfind_with_params(req, map.routing_params(), map)
     }
 
@@ -30,17 +31,17 @@ impl Pathfinder {
         req: PathRequest,
         params: &RoutingParams,
         map: &Map,
-    ) -> Option<Path> {
+    ) -> Option<PathV2> {
         if params != map.routing_params() {
             // If the params differ from the ones baked into the map, the CHs won't match. This
             // should only be happening from the debug UI; be very obnoxious if we start calling it
             // from the simulation or something else.
             warn!("Pathfinding slowly for {} with custom params", req);
-            return dijkstra::pathfind(req, params, map).map(|(path, _)| path);
+            return dijkstra::pathfind(req, params, map);
         }
 
         match self {
-            Pathfinder::Dijkstra => dijkstra::pathfind(req, params, map).map(|(path, _)| path),
+            Pathfinder::Dijkstra => dijkstra::pathfind(req, params, map),
             Pathfinder::CH(ref p) => p.pathfind(req, map),
         }
     }
@@ -52,8 +53,8 @@ impl Pathfinder {
         req: PathRequest,
         avoid: BTreeSet<RoadID>,
         map: &Map,
-    ) -> Option<Path> {
-        dijkstra::pathfind_avoiding_roads(req, avoid, map).map(|(path, _)| path)
+    ) -> Result<PathV2> {
+        dijkstra::pathfind_avoiding_roads(req, avoid, map)
     }
 
     // TODO Consider returning the walking-only path in the failure case, to avoid wasting work

map_model/src/pathfind/v2.rs

@@ -3,82 +3,181 @@
 //! things here will probably move into pathfind/mod.rs.
 
 use anyhow::Result;
+use serde::{Deserialize, Serialize};
+
+use geom::Duration;
 
 use crate::pathfind::uber_turns::UberTurnV2;
-use crate::{DirectedRoadID, Map, Path, PathConstraints, PathRequest, PathStep, TurnID, UberTurn};
+use crate::{
+    DirectedRoadID, Map, MovementID, Path, PathConstraints, PathRequest, PathStep, TurnID, UberTurn,
+};
 
-/// Transform a sequence of roads representing a path into the current lane-based path, by picking
-/// particular lanes and turns to use.
-pub fn path_v2_to_v1(
+/// One step along a path.
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub enum PathStepV2 {
+    /// Original direction
+    Along(DirectedRoadID),
+    /// Opposite direction, sidewalks only
+    Contraflow(DirectedRoadID),
+    Movement(MovementID),
+}
+
+/// A path between two endpoints for a particular mode. This representation is immutable and doesn't
+/// prescribe specific lanes and turns to follow.
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub struct PathV2 {
+    steps: Vec<PathStepV2>,
+    // TODO There will be a PathRequestV2, but I'm not sure how it'll change yet.
     req: PathRequest,
-    road_steps: Vec<DirectedRoadID>,
-    uber_turns_v2: Vec<UberTurnV2>,
-    map: &Map,
-) -> Result<Path> {
-    // This is a somewhat brute-force method: run Dijkstra's algorithm on a graph of lanes and
-    // turns, but only build the graph along the path of roads we've already found. This handles
-    // arbitrary lookahead needed, and forces use of the original start/end lanes requested.
-    //
-    // Eventually we'll directly return road-based paths. Most callers will actually just use that
-    // directly, and mainly the simulation will need to expand to specific lanes, but it'll do so
-    // dynamically/lazily to account for current traffic conditions.
-    let mut graph = petgraph::graphmap::DiGraphMap::new();
-    for pair in road_steps.windows(2) {
-        for src in pair[0].lanes(req.constraints, map) {
-            for dst in pair[1].lanes(req.constraints, map) {
-                let turn = TurnID {
-                    parent: map.get_l(src).dst_i,
-                    src,
-                    dst,
-                };
-                if map.maybe_get_t(turn).is_some() {
-                    graph.add_edge(src, dst, turn);
-                }
-            }
+    cost: Duration,
+    // TODO Temporarily we'll keep plumbing these along for path_v2_to_v1 to work, but we'll
+    // probably just discover uber-turns lazily at the simulation layer instead.
+    uber_turns: Vec<UberTurnV2>,
+}
+
+impl PathV2 {
+    pub(crate) fn new(
+        steps: Vec<PathStepV2>,
+        req: PathRequest,
+        cost: Duration,
+        uber_turns: Vec<UberTurnV2>,
+    ) -> PathV2 {
+        // TODO Port validate_continuity and validate_restrictions?
+        PathV2 {
+            steps,
+            req,
+            cost,
+            uber_turns,
         }
     }
 
-    match petgraph::algo::astar(
-        &graph,
-        req.start.lane(),
-        |l| l == req.end.lane(),
-        |(_, _, t)| {
-            // Normally opportunistic lane-changing adjusts the path live, but that doesn't work
-            // near uber-turns. So still use some of the penalties here.
-            let (lt, lc, slow_lane) = map.get_t(*t).penalty(map);
-            let mut extra_penalty = lt + lc;
-            if req.constraints == PathConstraints::Bike {
-                extra_penalty = slow_lane;
-            }
-            // Always treat every lane/turn as at least cost 1; otherwise A* can't understand that
-            // a final path with 10 steps costs more than one with 5. The road-based pathfinding
-            // has already chosen the overall route; when we're picking individual lanes, the
-            // length of each lane along one road is going to be about the same.
-            let base = 1;
-            base + extra_penalty
-        },
-        |_| 0,
-    ) {
-        Some((_, path)) => {
-            let mut steps = Vec::new();
-            for pair in path.windows(2) {
-                steps.push(PathStep::Lane(pair[0]));
-                // We don't need to look for this turn in the map; we know it exists.
-                steps.push(PathStep::Turn(TurnID {
-                    parent: map.get_l(pair[0]).dst_i,
-                    src: pair[0],
-                    dst: pair[1],
-                }));
-            }
-            steps.push(PathStep::Lane(req.end.lane()));
-            assert_eq!(steps[0], PathStep::Lane(req.start.lane()));
-            let uber_turns = find_uber_turns(&steps, map, uber_turns_v2);
-            Ok(Path::new(map, steps, req, uber_turns))
+    /// Vehicle implementations often just calculate the sequence of roads. Turn that into
+    /// PathStepV2 here.
+    pub(crate) fn from_roads(
+        mut roads: Vec<DirectedRoadID>,
+        req: PathRequest,
+        cost: Duration,
+        uber_turns: Vec<UberTurnV2>,
+        map: &Map,
+    ) -> PathV2 {
+        let mut steps = Vec::new();
+        for pair in roads.windows(2) {
+            steps.push(PathStepV2::Along(pair[0]));
+            steps.push(PathStepV2::Movement(MovementID {
+                from: pair[0],
+                to: pair[1],
+                parent: pair[0].dst_i(map),
+                crosswalk: false,
+            }));
         }
-        None => bail!(
-            "path_v2_to_v1 found road-based path, but not a lane-based path matching it for {}",
-            req
-        ),
+        steps.push(PathStepV2::Along(roads.pop().unwrap()));
+        PathV2::new(steps, req, cost, uber_turns)
+    }
+
+    /// The original PathRequest used to produce this path.
+    pub fn get_req(&self) -> &PathRequest {
+        &self.req
+    }
+
+    /// All steps in this path.
+    pub fn get_steps(&self) -> &Vec<PathStepV2> {
+        &self.steps
+    }
+
+    /// The time needed to perform this path. This time is not a lower bound; physically following
+    /// the path might be faster. This time incorporates costs like using sub-optimal lanes or
+    /// taking difficult turns.
+    pub fn get_cost(&self) -> Duration {
+        self.cost
+    }
+
+    /// Transform a sequence of roads representing a path into the current lane-based path, by
+    /// picking particular lanes and turns to use.
+    pub fn to_v1(self, map: &Map) -> Result<Path> {
+        if self.req.constraints == PathConstraints::Pedestrian {
+            return self.to_v1_walking(map);
+        }
+
+        // This is a somewhat brute-force method: run Dijkstra's algorithm on a graph of lanes and
+        // turns, but only build the graph along the path of roads we've already found. This handles
+        // arbitrary lookahead needed, and forces use of the original start/end lanes requested.
+        let mut graph = petgraph::graphmap::DiGraphMap::new();
+        for step in &self.steps {
+            if let PathStepV2::Movement(mvmnt) = step {
+                for src in mvmnt.from.lanes(self.req.constraints, map) {
+                    for dst in mvmnt.to.lanes(self.req.constraints, map) {
+                        let turn = TurnID {
+                            parent: map.get_l(src).dst_i,
+                            src,
+                            dst,
+                        };
+                        if map.maybe_get_t(turn).is_some() {
+                            graph.add_edge(src, dst, turn);
+                        }
+                    }
+                }
+            }
+        }
+
+        match petgraph::algo::astar(
+            &graph,
+            self.req.start.lane(),
+            |l| l == self.req.end.lane(),
+            |(_, _, t)| {
+                // Normally opportunistic lane-changing adjusts the path live, but that doesn't work
+                // near uber-turns. So still use some of the penalties here.
+                let (lt, lc, slow_lane) = map.get_t(*t).penalty(map);
+                let mut extra_penalty = lt + lc;
+                if self.req.constraints == PathConstraints::Bike {
+                    extra_penalty = slow_lane;
+                }
+                // Always treat every lane/turn as at least cost 1; otherwise A* can't understand
+                // that a final path with 10 steps costs more than one with 5. The
+                // road-based pathfinding has already chosen the overall route; when
+                // we're picking individual lanes, the length of each lane along one
+                // road is going to be about the same.
+                let base = 1;
+                base + extra_penalty
+            },
+            |_| 0,
+        ) {
+            Some((_, path)) => {
+                let mut steps = Vec::new();
+                for pair in path.windows(2) {
+                    steps.push(PathStep::Lane(pair[0]));
+                    // We don't need to look for this turn in the map; we know it exists.
+                    steps.push(PathStep::Turn(TurnID {
+                        parent: map.get_l(pair[0]).dst_i,
+                        src: pair[0],
+                        dst: pair[1],
+                    }));
+                }
+                steps.push(PathStep::Lane(self.req.end.lane()));
+                assert_eq!(steps[0], PathStep::Lane(self.req.start.lane()));
+                let uber_turns = find_uber_turns(&steps, map, self.uber_turns);
+                Ok(Path::new(map, steps, self.req, uber_turns))
+            }
+            None => bail!(
+                "Can't transform a road-based path to a lane-based path for {}",
+                self.req
+            ),
+        }
+    }
+
+    fn to_v1_walking(self, map: &Map) -> Result<Path> {
+        let mut steps = Vec::new();
+        for step in self.steps {
+            steps.push(match step {
+                PathStepV2::Along(r) => PathStep::Lane(r.must_get_sidewalk(map)),
+                PathStepV2::Contraflow(r) => PathStep::ContraflowLane(r.must_get_sidewalk(map)),
+                PathStepV2::Movement(mvmnt) => PathStep::Turn(TurnID {
+                    src: mvmnt.from.must_get_sidewalk(map),
+                    dst: mvmnt.to.must_get_sidewalk(map),
+                    parent: mvmnt.parent,
+                }),
+            });
+        }
+        Ok(Path::new(map, steps, self.req, Vec::new()))
     }
 }
 

map_model/src/pathfind/vehicles.rs

@@ -12,11 +12,10 @@ use geom::{Distance, Duration};
 use crate::pathfind::ch::round;
 use crate::pathfind::node_map::{deserialize_nodemap, NodeMap};
 use crate::pathfind::uber_turns::{IntersectionCluster, UberTurnV2};
-use crate::pathfind::v2::path_v2_to_v1;
 use crate::pathfind::zone_cost;
 use crate::{
-    DirectedRoadID, Direction, DrivingSide, LaneType, Map, MovementID, Path, PathConstraints,
-    PathRequest, RoadID, RoutingParams, Traversable, TurnType,
+    DirectedRoadID, Direction, DrivingSide, LaneType, Map, MovementID, PathConstraints,
+    PathRequest, PathV2, RoadID, RoutingParams, Traversable, TurnType,
 };
 
 #[derive(Serialize, Deserialize)]
@@ -93,7 +92,7 @@ impl VehiclePathfinder {
         }
     }
 
-    pub fn pathfind(&self, req: PathRequest, map: &Map) -> Option<(Path, Duration)> {
+    pub fn pathfind(&self, req: PathRequest, map: &Map) -> Option<PathV2> {
         assert!(!map.get_l(req.start.lane()).is_walkable());
         let mut calc = self
             .path_calc
@@ -120,14 +119,13 @@ impl VehiclePathfinder {
                         road_steps.push(mvmnt.to);
                     }
                     road_steps.pop();
-                    // Also remember the uber-turn exists, so we can reconstruct it in
-                    // path_v2_to_v1.
+                    // Also remember the uber-turn exists.
                     uber_turns.push(self.uber_turns[ut].clone());
                 }
             }
         }
-        let path = path_v2_to_v1(req, road_steps, uber_turns, map).ok()?;
-        Some((path, Duration::seconds(raw_path.get_weight() as f64)))
+        let cost = Duration::seconds(raw_path.get_weight() as f64);
+        Some(PathV2::from_roads(road_steps, req, cost, uber_turns, map))
     }
 
     pub fn apply_edits(&mut self, map: &Map) {

map_model/src/pathfind/walking.rs

@@ -16,8 +16,8 @@ use crate::pathfind::node_map::{deserialize_nodemap, NodeMap};
 use crate::pathfind::vehicles::VehiclePathfinder;
 use crate::pathfind::zone_cost;
 use crate::{
-    BusRoute, BusRouteID, BusStopID, DirectedRoadID, IntersectionID, Map, Path, PathConstraints,
-    PathRequest, PathStep, Position, Traversable,
+    BusRoute, BusRouteID, BusStopID, DirectedRoadID, IntersectionID, Map, MovementID,
+    PathConstraints, PathRequest, PathStepV2, PathV2, Position, Traversable,
 };
 
 #[derive(Serialize, Deserialize)]
@@ -107,7 +107,7 @@ impl SidewalkPathfinder {
         self.graph = fast_paths::prepare_with_order(&input_graph, &node_ordering).unwrap();
     }
 
-    pub fn pathfind(&self, req: PathRequest, map: &Map) -> Option<(Path, Duration)> {
+    pub fn pathfind(&self, req: PathRequest, map: &Map) -> Option<PathV2> {
         if req.start.lane() == req.end.lane() {
             return Some(one_step_walking_path(req, map));
         }
@@ -124,7 +124,7 @@ impl SidewalkPathfinder {
         let nodes = self.nodes.translate(&raw_path);
         let steps = walking_path_to_steps(nodes, map);
         let cost = Duration::seconds(raw_path.get_weight() as f64);
-        Some((Path::new(map, steps, req, Vec::new()), cost))
+        Some(PathV2::new(steps, req, cost, Vec::new()))
     }
 
     /// Attempt the pathfinding and see if we should ride a bus. If so, says (stop1, optional stop
@@ -328,10 +328,10 @@ fn transit_input_graph(
                 constraints: route.route_type,
             };
             let maybe_driving_cost = match route.route_type {
-                PathConstraints::Bus => bus_graph.pathfind(req, map).map(|(_, cost)| cost),
+                PathConstraints::Bus => bus_graph.pathfind(req, map).map(|p| p.get_cost()),
                 // We always use Dijkstra for trains
                 PathConstraints::Train => {
-                    dijkstra::pathfind(req, map.routing_params(), map).map(|(_, cost)| cost)
+                    dijkstra::pathfind(req, map.routing_params(), map).map(|p| p.get_cost())
                 }
                 _ => unreachable!(),
             };
@@ -357,10 +357,10 @@ fn transit_input_graph(
                 constraints: route.route_type,
             };
             let maybe_driving_cost = match route.route_type {
-                PathConstraints::Bus => bus_graph.pathfind(req, map).map(|(_, cost)| cost),
+                PathConstraints::Bus => bus_graph.pathfind(req, map).map(|p| p.get_cost()),
                 // We always use Dijkstra for trains
                 PathConstraints::Train => {
-                    dijkstra::pathfind(req, map.routing_params(), map).map(|(_, cost)| cost)
+                    dijkstra::pathfind(req, map.routing_params(), map).map(|p| p.get_cost())
                 }
                 _ => unreachable!(),
             };
@@ -404,11 +404,11 @@ fn transit_input_graph(
     }
 }
 
-pub fn walking_path_to_steps(path: Vec<WalkingNode>, map: &Map) -> Vec<PathStep> {
-    let mut steps: Vec<PathStep> = Vec::new();
+pub fn walking_path_to_steps(path: Vec<WalkingNode>, map: &Map) -> Vec<PathStepV2> {
+    let mut steps = Vec::new();
 
     for pair in path.windows(2) {
-        let (r1, l1_endpt) = match pair[0] {
+        let (r1, r1_endpt) = match pair[0] {
             WalkingNode::SidewalkEndpoint(r, endpt) => (r, endpt),
             WalkingNode::RideBus(_) => unreachable!(),
             WalkingNode::LeaveMap(_) => unreachable!(),
@@ -419,52 +419,59 @@ pub fn walking_path_to_steps(path: Vec<WalkingNode>, map: &Map) -> Vec<PathStep>
             WalkingNode::LeaveMap(_) => unreachable!(),
         };
 
-        let l1 = r1.must_get_sidewalk(map);
-        let l2 = r2.must_get_sidewalk(map);
-
-        if l1 == l2 {
-            if l1_endpt {
-                steps.push(PathStep::ContraflowLane(l1));
+        if r1 == r2 {
+            if r1_endpt {
+                steps.push(PathStepV2::Contraflow(r1));
             } else {
-                steps.push(PathStep::Lane(l1));
+                steps.push(PathStepV2::Along(r1));
             }
         } else {
-            let i = {
-                let l = map.get_l(l1);
-                if l1_endpt {
-                    l.dst_i
-                } else {
-                    l.src_i
-                }
+            let i = if r1_endpt {
+                r1.dst_i(map)
+            } else {
+                r1.src_i(map)
             };
-            // Could assert the intersection matches (l2, l2_endpt).
-            if let Some(turn) = map.get_turn_between(l1, l2, i) {
-                steps.push(PathStep::Turn(turn));
+            // Could assert the intersection matches (r2, r2_endpt).
+            if map
+                .get_turn_between(r1.must_get_sidewalk(map), r2.must_get_sidewalk(map), i)
+                .is_some()
+            {
+                steps.push(PathStepV2::Movement(MovementID {
+                    from: r1,
+                    to: r2,
+                    parent: i,
+                    crosswalk: true,
+                }));
             } else {
                 println!("walking_path_to_steps has a weird path:");
                 for s in &path {
                     println!("- {:?}", s);
                 }
-                panic!("No turn from {} to {} at {}", l1, l2, i);
+                panic!(
+                    "No turn from {} ({}) to {} ({}) at {}",
+                    r1,
+                    r1.must_get_sidewalk(map),
+                    r2,
+                    r2.must_get_sidewalk(map),
+                    i
+                );
             }
         }
     }
 
     // Don't start or end a path in a turn; sim layer breaks.
-    if let PathStep::Turn(t) = steps[0] {
-        let lane = map.get_l(t.src);
-        if lane.src_i == t.parent {
-            steps.insert(0, PathStep::ContraflowLane(lane.id));
+    if let PathStepV2::Movement(mvmnt) = steps[0] {
+        if mvmnt.from.src_i(map) == mvmnt.parent {
+            steps.insert(0, PathStepV2::Contraflow(mvmnt.from));
         } else {
-            steps.insert(0, PathStep::Lane(lane.id));
+            steps.insert(0, PathStepV2::Along(mvmnt.from));
         }
     }
-    if let PathStep::Turn(t) = steps.last().unwrap() {
-        let lane = map.get_l(t.dst);
-        if lane.src_i == t.parent {
-            steps.push(PathStep::Lane(lane.id));
+    if let PathStepV2::Movement(mvmnt) = steps.last().cloned().unwrap() {
+        if mvmnt.to.src_i(map) == mvmnt.parent {
+            steps.push(PathStepV2::Along(mvmnt.to));
         } else {
-            steps.push(PathStep::ContraflowLane(lane.id));
+            steps.push(PathStepV2::Contraflow(mvmnt.to));
         }
     }
 
@@ -472,15 +479,13 @@ pub fn walking_path_to_steps(path: Vec<WalkingNode>, map: &Map) -> Vec<PathStep>
 }
 
 // TODO Do we even need this at all?
-pub fn one_step_walking_path(req: PathRequest, map: &Map) -> (Path, Duration) {
+pub fn one_step_walking_path(req: PathRequest, map: &Map) -> PathV2 {
     // Weird case, but it can happen for walking from a building path to a bus stop that're
     // actually at the same spot.
-    let steps = if req.start.dist_along() == req.end.dist_along() {
-        vec![PathStep::Lane(req.start.lane())]
-    } else if req.start.dist_along() < req.end.dist_along() {
-        vec![PathStep::Lane(req.start.lane())]
+    let step = if req.start.dist_along() <= req.end.dist_along() {
+        PathStepV2::Along(map.get_l(req.start.lane()).get_directed_parent())
     } else {
-        vec![PathStep::ContraflowLane(req.start.lane())]
+        PathStepV2::Contraflow(map.get_l(req.start.lane()).get_directed_parent())
     };
     let mut cost = (req.start.dist_along() - req.end.dist_along()).abs()
         / Traversable::Lane(req.start.lane()).max_speed_along(
@@ -491,5 +496,5 @@ pub fn one_step_walking_path(req: PathRequest, map: &Map) -> (Path, Duration) {
     if map.get_l(req.start.lane()).is_shoulder() {
         cost = 2.0 * cost;
     }
-    (Path::new(map, steps, req, Vec::new()), cost)
+    PathV2::new(vec![step], req, cost, Vec::new())
 }

sim/src/cap.rs

@@ -108,13 +108,13 @@ impl CapSimState {
             }
         }
         match map.pathfind_avoiding_roads(path.get_req().clone(), avoid_roads) {
-            Some(path) => CapResult::Reroute(path),
-            None => {
+            Ok(path) => CapResult::Reroute(path),
+            Err(err) => {
                 if let Some(delay) = self.delay_trips_instead_of_cancelling {
                     CapResult::Delay(delay)
                 } else {
                     CapResult::Cancel {
-                        reason: format!("no path avoiding caps: {}", path.get_req()),
+                        reason: err.to_string(),
                     }
                 }
             }