Add tests for d3.geo.length.

Also return the perimeter for polygons.

d3.js

@@ -6485,12 +6485,8 @@ d3 = function() {
     point: d3_noop,
     lineStart: d3_geo_lengthLineStart,
     lineEnd: d3_noop,
-    polygonStart: function() {
-      d3_geo_length.lineStart = d3_noop;
-    },
-    polygonEnd: function() {
-      d3_geo_length.lineStart = d3_geo_lengthLineStart;
-    }
+    polygonStart: d3_noop,
+    polygonEnd: d3_noop
   };
   function d3_geo_lengthLineStart() {
     var λ0, sinφ0, cosφ0;

src/geo/length.js

@@ -11,15 +11,10 @@ var d3_geo_length = {
   point: d3_noop,
   lineStart: d3_geo_lengthLineStart,
   lineEnd: d3_noop,
-  polygonStart: function() {
-    d3_geo_length.lineStart = d3_noop;
-  },
-  polygonEnd: function() {
-    d3_geo_length.lineStart = d3_geo_lengthLineStart;
-  }
+  polygonStart: d3_noop,
+  polygonEnd: d3_noop
 };
 
-
 function d3_geo_lengthLineStart() {
   var λ0, sinφ0, cosφ0;
 
@@ -27,6 +22,7 @@ function d3_geo_lengthLineStart() {
     λ0 = λ * d3_radians, sinφ0 = Math.sin(φ *= d3_radians), cosφ0 = Math.cos(φ);
     d3_geo_length.point = nextPoint;
   };
+
   d3_geo_length.lineEnd = function() {
     d3_geo_length.point = d3_geo_length.lineEnd = d3_noop;
   };

test/geo/length-test.js

@@ -0,0 +1,47 @@
+require("../env");
+
+var vows = require("vows"),
+    assert = require("assert");
+
+var suite = vows.describe("d3.geo.length");
+
+var π = Math.PI;
+
+suite.addBatch({
+  "length": {
+    topic: function() {
+      return d3.geo.length;
+    },
+    "the length of points are zero": function(length) {
+      assert.inDelta(length({type: "Point", coordinates: [0, 0]}), 0, 1e-6);
+      assert.inDelta(length({type: "MultiPoint", coordinates: [[0, 1], [2, 3]]}), 0, 1e-6);
+    },
+    "the length of a line string is the sum of its great arc segments": function(length) {
+      assert.inDelta(length({type: "LineString", coordinates: [[-45, 0], [45, 0]]}), Math.PI / 2, 1e-6);
+      assert.inDelta(length({type: "LineString", coordinates: [[-45, 0], [-30, 0], [-15, 0], [0, 0]]}), Math.PI / 4, 1e-6);
+      assert.inDelta(length({type: "MultiLineString", coordinates: [[[-45, 0], [-30, 0]], [[-15, 0], [0, 0]]]}), Math.PI / 6, 1e-6);
+    },
+    "the length of a polygon is its perimeter": function(length) {
+      assert.inDelta(length({type: "Polygon", coordinates: [[[0, 0], [3, 0], [3, 3], [0, 3], [0, 0]]]}), 0.157008, 1e-6);
+      assert.inDelta(length({type: "MultiPolygon", coordinates: [[[[0, 0], [3, 0], [3, 3], [0, 3], [0, 0]]]]}), 0.157008, 1e-6);
+      assert.inDelta(length({type: "MultiPolygon", coordinates: [[[[0, 0], [3, 0], [3, 3], [0, 3], [0, 0]]], [[[1, 1], [2, 1], [2, 2], [1, 2], [1, 1]]]]}), 0.209354, 1e-6);
+    },
+    "the length of a polygon is its perimeter, including holes": function(length) {
+      assert.inDelta(length({type: "Polygon", coordinates: [[[0, 0], [3, 0], [3, 3], [0, 3], [0, 0]], [[1, 1], [2, 1], [2, 2], [1, 2], [1, 1]]]}), 0.209354, 1e-6);
+    },
+    "the length of a feature collection is the sum of its features": function(length) {
+      assert.inDelta(length({type: "FeatureCollection", features: [
+        {type: "Feature", geometry: {type: "LineString", coordinates: [[-45, 0], [0, 0]]}},
+        {type: "Feature", geometry: {type: "LineString", coordinates: [[0, 0], [45, 0]]}}
+      ]}), Math.PI / 2, 1e-6);
+    },
+    "the length of a geometry collection is the sum of its geometries": function(length) {
+      assert.inDelta(length({type: "GeometryCollection", geometries: [
+        {type: "GeometryCollection", geometries: [{type: "LineString", coordinates: [[-45, 0], [0, 0]]}]},
+        {type: "LineString", coordinates: [[0, 0], [45, 0]]}
+      ]}), Math.PI / 2, 1e-6);
+    }
+  }
+});
+
+suite.export(module);