deps: add thiserror and anyhow, reduce boilerplate

This adds rudimentary error messages and unsilences some errors.

Cargo.toml

@@ -12,6 +12,8 @@ pathfinder_geometry = { git = "https://github.com/servo/pathfinder" }
 pathfinder_gl = { git = "https://github.com/servo/pathfinder" }
 pathfinder_renderer = { git = "https://github.com/servo/pathfinder" }
 pathfinder_resources = { git = "https://github.com/servo/pathfinder" }
+thiserror = "1.0.56"
+anyhow = "1.0.79"
 
 [dependencies.geo]
 version = "0.25.1"

src/draw.rs

@@ -1,6 +1,6 @@
 use contracts::debug_ensures;
-
 use geo::{EuclideanLength, Point};
+use thiserror::Error;
 
 use crate::{
     graph::{
@@ -15,19 +15,18 @@ use crate::{
     rules::{Conditions, Rules},
 };
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Error, Debug, Clone, Copy)]
 pub enum DrawException {
-    NoTangents(NoTangents),
-    CannotFinishIn(FixedDotIndex, LayoutException),
+    #[error(transparent)]
+    NoTangents(#[from] NoTangents),
+    // TODO add real error messages + these should eventually use Display
+    #[error("cannot finish in {0:?}")]
+    CannotFinishIn(FixedDotIndex, #[source] LayoutException),
+    #[error("cannot wrap around {0:?}")]
+    // neither of the exceptions is the source on its own, might be useful to give them names?
     CannotWrapAround(WraparoundableIndex, LayoutException, LayoutException),
 }
 
-impl From<NoTangents> for DrawException {
-    fn from(err: NoTangents) -> Self {
-        DrawException::NoTangents(err)
-    }
-}
-
 pub struct Draw<'a> {
     layout: &'a mut Layout,
     rules: &'a Rules,

src/layout.rs

@@ -7,6 +7,7 @@ use petgraph::Direction::Incoming;
 use rstar::primitives::GeomWithData;
 use rstar::{RTree, RTreeObject};
 use slab::Slab;
+use thiserror::Error;
 
 use crate::graph::{
     BendWeight, DotIndex, DotWeight, FixedBendIndex, FixedDotIndex, FixedDotWeight, FixedSegIndex,
@@ -26,46 +27,30 @@ use crate::shape::{Shape, ShapeTrait};
 pub type RTreeWrapper = GeomWithData<Shape, Index>;
 
 #[enum_dispatch]
-#[derive(Debug, Clone, Copy)]
+#[derive(Error, Debug, Clone, Copy)]
 pub enum LayoutException {
-    NoTangents(NoTangents),
-    Infringement(Infringement),
-    Collision(Collision),
-    IsConnected(IsConnected),
+    #[error(transparent)]
+    NoTangents(#[from] NoTangents),
+    #[error(transparent)]
+    Infringement(#[from] Infringement),
+    #[error(transparent)]
+    Collision(#[from] Collision),
+    #[error(transparent)]
+    AlreadyConnected(#[from] AlreadyConnected),
 }
 
-impl From<NoTangents> for LayoutException {
-    fn from(err: NoTangents) -> Self {
-        LayoutException::NoTangents(err)
-    }
-}
-
-impl From<Infringement> for LayoutException {
-    fn from(err: Infringement) -> Self {
-        LayoutException::Infringement(err)
-    }
-}
-
-impl From<Collision> for LayoutException {
-    fn from(err: Collision) -> Self {
-        LayoutException::Collision(err)
-    }
-}
-
-impl From<IsConnected> for LayoutException {
-    fn from(err: IsConnected) -> Self {
-        LayoutException::IsConnected(err)
-    }
-}
-
-#[derive(Debug, Clone, Copy)]
+// TODO add real error messages + these should eventually use Display
+#[derive(Error, Debug, Clone, Copy)]
+#[error("{0:?} infringes on {1:?}")]
 pub struct Infringement(pub Shape, pub Index);
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Error, Debug, Clone, Copy)]
+#[error("{0:?} collides with {1:?}")]
 pub struct Collision(pub Shape, pub Index);
 
-#[derive(Debug, Clone, Copy)]
-pub struct IsConnected(pub i64, pub Index);
+#[derive(Error, Debug, Clone, Copy)]
+#[error("{1:?} is already connected to net {0}")]
+pub struct AlreadyConnected(pub i64, pub Index);
 
 #[derive(Debug, Clone, Copy)]
 pub struct Band {
@@ -152,7 +137,7 @@ impl Layout {
         self.insert_into_rtree(dot.into());
         self.fail_and_remove_if_infringes_except(dot.into(), infringables)?;
 
-        Ok::<GenericIndex<W>, Infringement>(dot)
+        Ok(dot)
     }
 
     #[debug_ensures(ret.is_ok() -> self.graph.node_count() == old(self.graph.node_count() + 1))]
@@ -471,8 +456,7 @@ impl Layout {
             .map_err(|err| {
                 self.remove(seg_to.into());
                 err
-            })
-            .map_err(|err| LayoutException::Infringement(err))?;
+            })?;
 
         let bend_to = self
             .add_dot_infringably(dot_weight, infringables)
@@ -480,8 +464,7 @@ impl Layout {
                 self.remove(seg.into());
                 self.remove(seg_to.into());
                 err
-            })
-            .map_err(|err| LayoutException::Infringement(err))?;
+            })?;
         let bend = self
             .add_loose_bend_infringably(seg_to, bend_to, around, bend_weight, infringables)
             .map_err(|err| {
@@ -571,10 +554,10 @@ impl Layout {
         let net = self.bands[weight.band].net;
         //
         if net == around.primitive(self).net() {
-            return Err(LayoutException::IsConnected(IsConnected(
+            return Err(AlreadyConnected(
                 net,
                 around.into(),
-            )));
+            ).into());
         }
         //
         if let Some(wraparound) = match around {
@@ -583,10 +566,10 @@ impl Layout {
             WraparoundableIndex::LooseBend(around) => self.primitive(around).wraparound(),
         } {
             if net == wraparound.primitive(self).net() {
-                return Err(LayoutException::IsConnected(IsConnected(
+                return Err(AlreadyConnected(
                     net,
                     wraparound.into(),
-                )));
+                ).into());
             }
         }
 
@@ -673,7 +656,7 @@ impl Layout {
 
         self.insert_into_rtree(bend.into());
         self.fail_and_remove_if_infringes_except(bend.into(), infringables)?;
-        Ok::<LooseBendIndex, Infringement>(bend)
+        Ok(bend)
     }
 
     #[debug_ensures(self.graph.node_count() == old(self.graph.node_count()))]

src/main.rs

@@ -31,7 +31,7 @@ use layout::{Infringement, Layout, LayoutException};
 use mesh::{Mesh, MeshEdgeReference, VertexIndex};
 use petgraph::visit::{EdgeRef, IntoEdgeReferences};
 use primitive::MakeShape;
-use router::RouterObserver;
+use router::{RouterObserver, RoutingError};
 
 use sdl2::event::Event;
 use sdl2::keyboard::Keycode;
@@ -175,7 +175,7 @@ impl<'a> RouterObserver for DebugRouterObserver<'a> {
     fn on_estimate(&mut self, _tracer: &Tracer, _vertex: VertexIndex) {}
 }
 
-fn main() {
+fn main() -> Result<(), anyhow::Error> {
     let sdl_context = sdl2::init().unwrap();
     let video_subsystem = sdl_context.video().unwrap();
 
@@ -488,7 +488,7 @@ fn main() {
         dot_end,
         &mut EmptyRouterObserver,
         //&mut DebugRouterObserver::new(&mut event_pump, &window, &mut renderer, &font_context),
-    );
+    )?;
 
     render_times(
         &mut event_pump,
@@ -521,7 +521,7 @@ fn main() {
         dot_end2,
         //&mut EmptyRouterObserver,
         &mut DebugRouterObserver::new(&mut event_pump, &window, &mut renderer, &font_context),
-    );
+    )?;
 
     render_times(
         &mut event_pump,
@@ -542,7 +542,7 @@ fn main() {
         dot_start3,
         dot_end3,
         &mut DebugRouterObserver::new(&mut event_pump, &window, &mut renderer, &font_context),
-    );
+    )?;
 
     render_times(
         &mut event_pump,
@@ -558,6 +558,8 @@ fn main() {
         &[],
         -1,
     );
+
+    Ok(())
 }
 
 fn render_times(

src/math.rs

@@ -1,7 +1,9 @@
 use geo::{geometry::Point, point, EuclideanDistance, Line};
 use std::ops::Sub;
+use thiserror::Error;
 
-#[derive(Debug, Clone, Copy, PartialEq)]
+#[derive(Error, Debug, Clone, Copy, PartialEq)]
+#[error("no tangents for {0:?} and {1:?}")] // TODO add real error message
 pub struct NoTangents(pub Circle, pub Circle);
 
 #[derive(Debug, Clone, Copy, PartialEq)]

src/router.rs

@@ -1,6 +1,7 @@
 use geo::geometry::Point;
 use petgraph::visit::EdgeRef;
 use spade::InsertionError;
+use thiserror::Error;
 
 use crate::astar::{astar, AstarStrategy, PathTracker};
 use crate::draw::DrawException;
@@ -12,6 +13,24 @@ use crate::mesh::{Mesh, MeshEdgeReference, VertexIndex};
 use crate::rules::Rules;
 use crate::tracer::{Trace, Tracer};
 
+#[derive(Error, Debug, Clone, Copy)]
+#[error("failed to route from {from:?} to {to:?}")] // this should eventually use Display
+pub struct RoutingError {
+    from: FixedDotIndex,
+    to: FixedDotIndex,
+    source: RoutingErrorKind,
+}
+
+#[derive(Error, Debug, Clone, Copy)]
+pub enum RoutingErrorKind {
+    #[error(transparent)]
+    MeshInsertion(#[from] InsertionError),
+    // exposing more details here seems difficult
+    // TODO more descriptive message
+    #[error("A* found no path")]
+    AStar,
+}
+
 pub trait RouterObserver {
     fn on_rework(&mut self, tracer: &Tracer, trace: &Trace);
     fn before_probe(&mut self, tracer: &Tracer, trace: &Trace, edge: MeshEdgeReference);
@@ -97,12 +116,17 @@ impl Router {
         from: FixedDotIndex,
         to: FixedDotIndex,
         observer: &mut impl RouterObserver,
-    ) -> Result<Mesh, InsertionError> {
+    ) -> Result<Mesh, RoutingError> {
         // XXX: Should we actually store the mesh? May be useful for debugging, but doesn't look
         // right.
         //self.mesh.triangulate(&self.layout)?;
         let mut mesh = Mesh::new(&self.layout);
-        mesh.generate(&self.layout)?;
+        mesh.generate(&self.layout)
+            .map_err(|err| RoutingError {
+                from,
+                to,
+                source: err.into(),
+            })?;
 
         let mut tracer = self.tracer(&mesh);
         let trace = tracer.start(from, 3.0);
@@ -111,8 +135,11 @@ impl Router {
             &mesh,
             from.into(),
             &mut RouterAstarStrategy::new(tracer, trace, to.into(), observer),
-        )
-        .unwrap(); // TODO.
+        ).ok_or(RoutingError {
+            from,
+            to,
+            source: RoutingErrorKind::AStar,
+        })?;
 
         Ok(mesh)
     }