From fd935b238f096b9982a20ad832379c363128a399 Mon Sep 17 00:00:00 2001
From: Michael Kirk <michael.code@endoftheworl.de>
Date: Thu, 31 Oct 2024 16:00:29 -0700
Subject: [PATCH 1/4] InterpolatePoint: handle some reasonable edge cases,
 document current behavior in tests.

---
 geo/CHANGES.md                                |   1 +
 .../line_measures/interpolate_point.rs        | 156 ++++++++++++++++++
 .../line_measures/metric_spaces/geodesic.rs   |  10 ++
 .../line_measures/metric_spaces/haversine.rs  |   6 +
 4 files changed, 173 insertions(+)

diff --git a/geo/CHANGES.md b/geo/CHANGES.md
index ad1f414b0..b9961991c 100644
--- a/geo/CHANGES.md
+++ b/geo/CHANGES.md
@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+* Improve handling of InterploatePoint with collapsed Line
 
 ## 0.29.0 - 2024.10.30
 
diff --git a/geo/src/algorithm/line_measures/interpolate_point.rs b/geo/src/algorithm/line_measures/interpolate_point.rs
index d53bc226e..9f653b966 100644
--- a/geo/src/algorithm/line_measures/interpolate_point.rs
+++ b/geo/src/algorithm/line_measures/interpolate_point.rs
@@ -32,3 +32,159 @@ pub trait InterpolatePoint<F: CoordFloat> {
         include_ends: bool,
     ) -> impl Iterator<Item = Point<F>>;
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::{Euclidean, Geodesic, Haversine, InterpolatePoint, Point, Rhumb};
+
+    #[test]
+    fn point_at_ratio_between_line_ends() {
+        let start = Point::new(0.0, 0.0);
+        let end = Point::new(1.0, 1.0);
+
+        let ratio = 0.0;
+        assert_eq!(Haversine::point_at_ratio_between(start, end, ratio), start);
+        assert_eq!(Euclidean::point_at_ratio_between(start, end, ratio), start);
+        assert_eq!(Geodesic::point_at_ratio_between(start, end, ratio), start);
+        assert_eq!(Rhumb::point_at_ratio_between(start, end, ratio), start);
+
+        let ratio = 1.0;
+        assert_eq!(Haversine::point_at_ratio_between(start, end, ratio), end);
+        assert_eq!(Euclidean::point_at_ratio_between(start, end, ratio), end);
+        assert_eq!(Geodesic::point_at_ratio_between(start, end, ratio), end);
+        assert_eq!(Rhumb::point_at_ratio_between(start, end, ratio), end);
+    }
+
+    mod degenerate {
+        use super::*;
+
+        #[test]
+        fn point_at_ratio_between_collapsed_line() {
+            let start = Point::new(1.0, 1.0);
+
+            let ratio = 0.0;
+            assert_eq!(
+                Haversine::point_at_ratio_between(start, start, ratio),
+                start
+            );
+            assert_eq!(
+                Euclidean::point_at_ratio_between(start, start, ratio),
+                start
+            );
+            assert_eq!(Geodesic::point_at_ratio_between(start, start, ratio), start);
+            assert_eq!(Rhumb::point_at_ratio_between(start, start, ratio), start);
+
+            let ratio = 0.5;
+            assert_eq!(
+                Haversine::point_at_ratio_between(start, start, ratio),
+                start
+            );
+            assert_eq!(
+                Euclidean::point_at_ratio_between(start, start, ratio),
+                start
+            );
+            assert_eq!(Geodesic::point_at_ratio_between(start, start, ratio), start);
+            assert_eq!(Rhumb::point_at_ratio_between(start, start, ratio), start);
+
+            let ratio = 1.0;
+            assert_eq!(
+                Haversine::point_at_ratio_between(start, start, ratio),
+                start
+            );
+            assert_eq!(
+                Euclidean::point_at_ratio_between(start, start, ratio),
+                start
+            );
+            assert_eq!(Geodesic::point_at_ratio_between(start, start, ratio), start);
+            assert_eq!(Rhumb::point_at_ratio_between(start, start, ratio), start);
+        }
+
+        #[test]
+        fn point_at_distance_between_collapsed_line() {
+            // This method just documents existing behavior. I don't think our current behavior
+            // is especially useful, but we might consider handling it uniformly one day.
+            let start: Point = Point::new(1.0, 1.0);
+
+            let distance = 0.0;
+            assert_eq!(
+                Haversine::point_at_distance_between(start, start, distance),
+                start
+            );
+
+            let euclidean_result = Euclidean::point_at_distance_between(start, start, distance);
+            assert!(euclidean_result.x().is_nan());
+            assert!(euclidean_result.y().is_nan());
+            assert_eq!(
+                Geodesic::point_at_distance_between(start, start, distance),
+                start
+            );
+            assert_eq!(
+                Rhumb::point_at_distance_between(start, start, distance),
+                start
+            );
+
+            let distance = 100000.0;
+            let due_north = Point::new(1.0, 1.9);
+            let due_south = Point::new(1.0, 0.1);
+            assert_relative_eq!(
+                Haversine::point_at_distance_between(start, start, distance),
+                due_north,
+                epsilon = 1.0e-1
+            );
+            let euclidean_result = Euclidean::point_at_distance_between(start, start, distance);
+            assert!(euclidean_result.x().is_nan());
+            assert!(euclidean_result.y().is_nan());
+            assert_relative_eq!(
+                Geodesic::point_at_distance_between(start, start, distance),
+                due_south,
+                epsilon = 1.0e-1
+            );
+            assert_relative_eq!(
+                Rhumb::point_at_distance_between(start, start, distance),
+                due_north,
+                epsilon = 1.0e-1
+            );
+        }
+
+        #[test]
+        fn points_along_collapsed_line() {
+            let start = Point::new(1.0, 1.0);
+
+            let max_distance = 1.0;
+
+            let include_ends = true;
+            let points: Vec<_> =
+                Haversine::points_along_line(start, start, max_distance, include_ends).collect();
+            assert_eq!(points, vec![start, start]);
+
+            let points: Vec<_> =
+                Euclidean::points_along_line(start, start, max_distance, include_ends).collect();
+            assert_eq!(points, vec![start, start]);
+
+            let points: Vec<_> =
+                Geodesic::points_along_line(start, start, max_distance, include_ends).collect();
+            assert_eq!(points, vec![start, start]);
+
+            let points: Vec<_> =
+                Rhumb::points_along_line(start, start, max_distance, include_ends).collect();
+            assert_eq!(points, vec![start, start]);
+
+            let include_ends = false;
+            let points: Vec<_> =
+                Haversine::points_along_line(start, start, max_distance, include_ends).collect();
+            assert_eq!(points, vec![]);
+
+            let points: Vec<_> =
+                Euclidean::points_along_line(start, start, max_distance, include_ends).collect();
+            assert_eq!(points, vec![]);
+
+            let points: Vec<_> =
+                Geodesic::points_along_line(start, start, max_distance, include_ends).collect();
+            assert_eq!(points, vec![]);
+
+            let points: Vec<_> =
+                Rhumb::points_along_line(start, start, max_distance, include_ends).collect();
+            assert_eq!(points, vec![]);
+        }
+    }
+}
diff --git a/geo/src/algorithm/line_measures/metric_spaces/geodesic.rs b/geo/src/algorithm/line_measures/metric_spaces/geodesic.rs
index 6e9ccb874..89335ca87 100644
--- a/geo/src/algorithm/line_measures/metric_spaces/geodesic.rs
+++ b/geo/src/algorithm/line_measures/metric_spaces/geodesic.rs
@@ -168,6 +168,9 @@ impl InterpolatePoint<f64> for Geodesic {
         end: Point<f64>,
         meters_from_start: f64,
     ) -> Point<f64> {
+        if meters_from_start == 0.0 {
+            return start;
+        }
         let bearing = Self::bearing(start, end);
         Self::destination(start, bearing, meters_from_start)
     }
@@ -205,6 +208,13 @@ impl InterpolatePoint<f64> for Geodesic {
         end: Point<f64>,
         ratio_from_start: f64,
     ) -> Point<f64> {
+        if start == end || ratio_from_start == 0.0 {
+            return start;
+        }
+        if ratio_from_start == 1.0 {
+            return end;
+        }
+
         let g = geographiclib_rs::Geodesic::wgs84();
         let (total_distance, azi1, _azi2, _a12) = g.inverse(start.y(), start.x(), end.y(), end.x());
         let distance = total_distance * ratio_from_start;
diff --git a/geo/src/algorithm/line_measures/metric_spaces/haversine.rs b/geo/src/algorithm/line_measures/metric_spaces/haversine.rs
index 971e7504e..ac4b02479 100644
--- a/geo/src/algorithm/line_measures/metric_spaces/haversine.rs
+++ b/geo/src/algorithm/line_measures/metric_spaces/haversine.rs
@@ -204,6 +204,12 @@ impl<F: CoordFloat + FromPrimitive> InterpolatePoint<F> for Haversine {
     ///
     /// [great circle]: https://en.wikipedia.org/wiki/Great_circle
     fn point_at_ratio_between(start: Point<F>, end: Point<F>, ratio_from_start: F) -> Point<F> {
+        if start == end || ratio_from_start == F::zero() {
+            return start;
+        }
+        if ratio_from_start == F::one() {
+            return end;
+        }
         let calculation = HaversineIntermediateFillCalculation::new(start, end);
         calculation.point_at_ratio(ratio_from_start)
     }

From 6e5b7195b7e05deebcd55f60c503602c55a91bb0 Mon Sep 17 00:00:00 2001
From: Corey Farwell <coreyf@rwell.org>
Date: Thu, 31 Oct 2024 22:00:58 -0400
Subject: [PATCH 2/4] Allow configuring of the `i_overlay` dep, Rayon
 transitive dep, and document more features.

---
 .github/workflows/test.yml              |  2 +-
 geo/Cargo.toml                          |  5 +++--
 geo/src/algorithm/bool_ops/mod.rs       |  2 ++
 geo/src/algorithm/mod.rs                |  8 +++++++-
 geo/src/algorithm/triangulate_earcut.rs |  2 ++
 geo/src/lib.rs                          | 26 ++++++++++++++++++++-----
 6 files changed, 36 insertions(+), 9 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index ddf68ef01..cdbf06f9b 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -116,7 +116,7 @@ jobs:
         uses: actions/checkout@v3
       - run: cargo check --all-targets --no-default-features
       # we don't want to test `proj-network` because it only enables the `proj` feature
-      - run: cargo test --features "use-proj use-serde"
+      - run: cargo test --features "use-proj use-serde i_overlay earcutr multithreading"
 
   geo_traits:
     name: geo-traits
diff --git a/geo/Cargo.toml b/geo/Cargo.toml
index c8cc5f188..9c29776ce 100644
--- a/geo/Cargo.toml
+++ b/geo/Cargo.toml
@@ -13,10 +13,11 @@ rust-version = "1.75"
 categories = ["science::geo"]
 
 [features]
-default = ["earcutr", "spade"]
+default = ["earcutr", "spade", "i_overlay", "multithreading"]
 use-proj = ["proj"]
 proj-network = ["use-proj", "proj/network"]
 use-serde = ["serde", "geo-types/serde"]
+multithreading = ["i_overlay/allow_multithreading"]
 
 [dependencies]
 earcutr = { version = "0.4.2", optional = true }
@@ -30,7 +31,7 @@ proj = { version = "0.27.0", optional = true }
 robust = "1.1.0"
 rstar = "0.12.0"
 serde = { version = "1.0", optional = true, features = ["derive"] }
-i_overlay = "1.7.2"
+i_overlay = { version = "1.7.2", optional = true }
 
 [dev-dependencies]
 approx = ">= 0.4.0, < 0.6.0"
diff --git a/geo/src/algorithm/bool_ops/mod.rs b/geo/src/algorithm/bool_ops/mod.rs
index 16287b049..aa5abdf02 100644
--- a/geo/src/algorithm/bool_ops/mod.rs
+++ b/geo/src/algorithm/bool_ops/mod.rs
@@ -8,6 +8,8 @@ use crate::geometry::{LineString, MultiLineString, MultiPolygon, Polygon};
 
 /// Boolean Operations on geometry.
 ///
+/// Requires the `"i_overlay"` feature, which is enabled by default.
+///
 /// Boolean operations are set operations on geometries considered as a subset
 /// of the 2-D plane. The operations supported are: intersection, union, xor or
 /// symmetric difference, and set-difference on pairs of 2-D geometries and
diff --git a/geo/src/algorithm/mod.rs b/geo/src/algorithm/mod.rs
index 344084dc3..b47f1c56d 100644
--- a/geo/src/algorithm/mod.rs
+++ b/geo/src/algorithm/mod.rs
@@ -6,8 +6,12 @@ pub use kernels::{Kernel, Orientation};
 pub mod area;
 pub use area::Area;
 
-/// Boolean Ops such as union, xor, difference;
+/// Boolean Ops such as union, xor, difference.
+///
+/// Requires the `"i_overlay"` feature, which is enabled by default.
+#[cfg(feature = "i_overlay")]
 pub mod bool_ops;
+#[cfg(feature = "i_overlay")]
 pub use bool_ops::{BooleanOps, OpType};
 
 /// Calculate the bounding rectangle of a `Geometry`.
@@ -254,6 +258,8 @@ pub mod translate;
 pub use translate::Translate;
 
 /// Triangulate polygons using an [ear-cutting algorithm](https://www.geometrictools.com/Documentation/TriangulationByEarClipping.pdf).
+///
+/// Requires the `"earcutr"` feature.
 #[cfg(feature = "earcutr")]
 pub mod triangulate_earcut;
 #[cfg(feature = "earcutr")]
diff --git a/geo/src/algorithm/triangulate_earcut.rs b/geo/src/algorithm/triangulate_earcut.rs
index d4d23df32..586f3cb3d 100644
--- a/geo/src/algorithm/triangulate_earcut.rs
+++ b/geo/src/algorithm/triangulate_earcut.rs
@@ -1,6 +1,8 @@
 use crate::{coord, CoordFloat, CoordsIter, Polygon, Triangle};
 
 /// Triangulate polygons using an [ear-cutting algorithm](https://www.geometrictools.com/Documentation/TriangulationByEarClipping.pdf).
+///
+/// Requires the `"earcutr"` feature, which is enabled by default.
 pub trait TriangulateEarcut<T: CoordFloat> {
     /// # Examples
     ///
diff --git a/geo/src/lib.rs b/geo/src/lib.rs
index 11cf8bc4a..ff5bdf94a 100644
--- a/geo/src/lib.rs
+++ b/geo/src/lib.rs
@@ -67,7 +67,7 @@
 //!
 //! ## Boolean Operations
 //!
-//! - **[`BooleanOps`]**: combine or split (Multi)Polygons using intersecton, union, xor, or difference operations
+//! - **[`BooleanOps`]**: combine or split (Multi)Polygons using intersecton, union, xor, or difference operations. Requires the `"i_overlay"` feature, which is enabled by default.
 //!
 //! ## Outlier Detection
 //!
@@ -112,7 +112,7 @@
 //!
 //! ## Triangulation
 //!
-//! - **[`TriangulateEarcut`](triangulate_earcut)**: Triangulate polygons using the earcut algorithm (requires the `earcutr` feature).
+//! - **[`TriangulateEarcut`](triangulate_earcut)**: Triangulate polygons using the earcut algorithm. Requires the `"earcutr"` feature, which is enabled by default.
 //!
 //! ## Winding
 //!
@@ -177,9 +177,25 @@
 //!
 //! The following optional [Cargo features] are available:
 //!
-//! - `proj-network`: Enables [network grid] support for the [`proj` crate]. After enabling this feature, [further configuration][proj crate file download] is required to use the network grid
-//! - `use-proj`: Enables coordinate conversion and transformation of `Point` geometries using the [`proj` crate]
-//! - `use-serde`: Allows geometry types to be serialized and deserialized with [Serde]
+//! - `i_overlay`:
+//!     - Enables the `i_overlay` crate, which provides boolean operations on geometries.
+//!     - ☑ Enabled by default.
+//! - `earcutr`:
+//!     - Enables the `earcutr` crate, which provides triangulation of polygons using the earcut algorithm.
+//!     - ☑ Enabled by default.
+//! - `proj-network`:
+//!     - Enables [network grid] support for the [`proj` crate].
+//!     - After enabling this feature, [further configuration][proj crate file download] is required to use the network grid.
+//!     - ☐ Disabled by default.
+//! - `use-proj`:
+//!     - Enables coordinate conversion and transformation of `Point` geometries using the [`proj` crate]
+//!     - ☐ Disabled by default.
+//! - `use-serde`:
+//!     - Allows geometry types to be serialized and deserialized with [Serde].
+//!     - ☐ Disabled by default.
+//! - `multithreading`:
+//!     - Enables multithreading support for the `i_overlay` crate.
+//!     - ☑ Enabled by default.
 //!
 //! # Ecosystem
 //!

From 6e2303904d3b3470e683f194a8e21cbe3786fa67 Mon Sep 17 00:00:00 2001
From: Corey Farwell <coreyf@rwell.org>
Date: Fri, 1 Nov 2024 12:21:52 -0400
Subject: [PATCH 3/4] Update Cargo.toml

---
 geo/Cargo.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/geo/Cargo.toml b/geo/Cargo.toml
index 9c29776ce..dd6b8ebb0 100644
--- a/geo/Cargo.toml
+++ b/geo/Cargo.toml
@@ -31,7 +31,7 @@ proj = { version = "0.27.0", optional = true }
 robust = "1.1.0"
 rstar = "0.12.0"
 serde = { version = "1.0", optional = true, features = ["derive"] }
-i_overlay = { version = "1.7.2", optional = true }
+i_overlay = { version = "1.7.2", optional = true, default-features = false }
 
 [dev-dependencies]
 approx = ">= 0.4.0, < 0.6.0"

From c85ed96fec60fd10bd452e49d461c6856c3103b5 Mon Sep 17 00:00:00 2001
From: Corey Farwell <coreyf@rwell.org>
Date: Fri, 1 Nov 2024 14:54:31 -0400
Subject: [PATCH 4/4] apply changes

---
 .github/workflows/test.yml        | 2 +-
 geo/Cargo.toml                    | 4 ++--
 geo/src/algorithm/bool_ops/mod.rs | 2 --
 geo/src/algorithm/mod.rs          | 4 ----
 geo/src/lib.rs                    | 5 +----
 5 files changed, 4 insertions(+), 13 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index cdbf06f9b..598c60b2c 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -116,7 +116,7 @@ jobs:
         uses: actions/checkout@v3
       - run: cargo check --all-targets --no-default-features
       # we don't want to test `proj-network` because it only enables the `proj` feature
-      - run: cargo test --features "use-proj use-serde i_overlay earcutr multithreading"
+      - run: cargo test --features "use-proj use-serde earcutr multithreading"
 
   geo_traits:
     name: geo-traits
diff --git a/geo/Cargo.toml b/geo/Cargo.toml
index 9c29776ce..b9a63b277 100644
--- a/geo/Cargo.toml
+++ b/geo/Cargo.toml
@@ -13,7 +13,7 @@ rust-version = "1.75"
 categories = ["science::geo"]
 
 [features]
-default = ["earcutr", "spade", "i_overlay", "multithreading"]
+default = ["earcutr", "spade", "multithreading"]
 use-proj = ["proj"]
 proj-network = ["use-proj", "proj/network"]
 use-serde = ["serde", "geo-types/serde"]
@@ -31,7 +31,7 @@ proj = { version = "0.27.0", optional = true }
 robust = "1.1.0"
 rstar = "0.12.0"
 serde = { version = "1.0", optional = true, features = ["derive"] }
-i_overlay = { version = "1.7.2", optional = true }
+i_overlay = "1.7.2"
 
 [dev-dependencies]
 approx = ">= 0.4.0, < 0.6.0"
diff --git a/geo/src/algorithm/bool_ops/mod.rs b/geo/src/algorithm/bool_ops/mod.rs
index aa5abdf02..16287b049 100644
--- a/geo/src/algorithm/bool_ops/mod.rs
+++ b/geo/src/algorithm/bool_ops/mod.rs
@@ -8,8 +8,6 @@ use crate::geometry::{LineString, MultiLineString, MultiPolygon, Polygon};
 
 /// Boolean Operations on geometry.
 ///
-/// Requires the `"i_overlay"` feature, which is enabled by default.
-///
 /// Boolean operations are set operations on geometries considered as a subset
 /// of the 2-D plane. The operations supported are: intersection, union, xor or
 /// symmetric difference, and set-difference on pairs of 2-D geometries and
diff --git a/geo/src/algorithm/mod.rs b/geo/src/algorithm/mod.rs
index b47f1c56d..6f92320cf 100644
--- a/geo/src/algorithm/mod.rs
+++ b/geo/src/algorithm/mod.rs
@@ -7,11 +7,7 @@ pub mod area;
 pub use area::Area;
 
 /// Boolean Ops such as union, xor, difference.
-///
-/// Requires the `"i_overlay"` feature, which is enabled by default.
-#[cfg(feature = "i_overlay")]
 pub mod bool_ops;
-#[cfg(feature = "i_overlay")]
 pub use bool_ops::{BooleanOps, OpType};
 
 /// Calculate the bounding rectangle of a `Geometry`.
diff --git a/geo/src/lib.rs b/geo/src/lib.rs
index ff5bdf94a..88bf61aa8 100644
--- a/geo/src/lib.rs
+++ b/geo/src/lib.rs
@@ -67,7 +67,7 @@
 //!
 //! ## Boolean Operations
 //!
-//! - **[`BooleanOps`]**: combine or split (Multi)Polygons using intersecton, union, xor, or difference operations. Requires the `"i_overlay"` feature, which is enabled by default.
+//! - **[`BooleanOps`]**: combine or split (Multi)Polygons using intersecton, union, xor, or difference operations.
 //!
 //! ## Outlier Detection
 //!
@@ -177,9 +177,6 @@
 //!
 //! The following optional [Cargo features] are available:
 //!
-//! - `i_overlay`:
-//!     - Enables the `i_overlay` crate, which provides boolean operations on geometries.
-//!     - ☑ Enabled by default.
 //! - `earcutr`:
 //!     - Enables the `earcutr` crate, which provides triangulation of polygons using the earcut algorithm.
 //!     - ☑ Enabled by default.