Close rings if necessary

Author: trasch

Sources/GISTools/Algorithms/Union.swift …s/GISTools/Algorithms/PolygonUnion.swiftSources/GISTools/Algorithms/Union.swift renamed to Sources/GISTools/Algorithms/PolygonUnion.swift Sources/GISTools/Algorithms/Union.swift renamed to Sources/GISTools/Algorithms/PolygonUnion.swift

@@ -34,7 +34,7 @@ public struct Polygon:
 
     /// The receiver's outer ring.
     public var outerRing: Ring? {
-        guard !coordinates.isEmpty else { return nil }
+        guard coordinates.isNotEmpty else { return nil }
         return Ring(coordinates[0])
     }
 
@@ -55,7 +55,7 @@ public struct Polygon:
 
     /// Try to initialize a Polygon with some coordinates.
     public init?(_ coordinates: [[Coordinate3D]], calculateBoundingBox: Bool = false) {
-        guard !coordinates.isEmpty,
+        guard coordinates.isNotEmpty,
               coordinates[0].count >= 3
         else { return nil }
 

Sources/GISTools/GeoJson/Polygon.swift

@@ -29,7 +29,14 @@ public struct Ring: Sendable {
 
     /// Try to initialize a Ring with some coordinates.
     public init?(_ coordinates: [Coordinate3D]) {
-        // TODO: Close the ring, if necessary
+        // Close the ring, if necessary
+        var coordinates = coordinates
+        if coordinates.count >= 3,
+           coordinates.first != coordinates.last
+        {
+            coordinates.append(coordinates[0])
+        }
+
         guard coordinates.count >= 4 else { return nil }
 
         self.init(unchecked: coordinates)