v3 stuff, add test

src/controllers/controller.polarArea.js

@@ -107,9 +107,9 @@ defaults._set('polarArea', {
 });
 
 function getStartAngleRadians(deg) {
-	// radianLinear scale draws angleLines using startAngle. 0 is excepted to be at top.
+	// radialLinear scale draws angleLines using startAngle. 0 is excepted to be at top.
 	// Here we adjust to standard unit circle used in drawing, where 0 is at right.
-	return helpers.toRadians(deg) - 0.5 * Math.PI;
+	return helpers.math.toRadians(deg) - 0.5 * Math.PI;
 }
 
 module.exports = DatasetController.extend({

src/helpers/helpers.math.js

@@ -83,11 +83,11 @@ export const sign = Math.sign ?
 	};
 
 export function toRadians(degrees) {
-	return degrees * (Math.PI / 180);
+	return degrees * (PI / 180);
 }
 
 export function toDegrees(radians) {
-	return radians * (180 / Math.PI);
+	return radians * (180 / PI);
 }
 
 /**
@@ -118,8 +118,8 @@ export function getAngleFromPoint(centrePoint, anglePoint) {
 
 	var angle = Math.atan2(distanceFromYCenter, distanceFromXCenter);
 
-	if (angle < (-0.5 * Math.PI)) {
-		angle += 2.0 * Math.PI; // make sure the returned angle is in the range of (-PI/2, 3PI/2]
+	if (angle < (-0.5 * PI)) {
+		angle += TAU; // make sure the returned angle is in the range of (-PI/2, 3PI/2]
 	}
 
 	return {

src/scales/scale.radialLinear.js

@@ -2,7 +2,7 @@
 
 import defaults from '../core/core.defaults';
 import helpers from '../helpers/index';
-import {isNumber, toDegrees} from '../helpers/helpers.math';
+import {isNumber, toDegrees, toRadians, _normalizeAngle} from '../helpers/helpers.math';
 import LinearScaleBase from './scale.linearbase';
 import Ticks from '../core/core.ticks';
 
@@ -157,7 +157,7 @@ function fitWithPointLabels(scale) {
 
 		// Add quarter circle to make degree 0 mean top of circle
 		var angleRadians = scale.getIndexAngle(i);
-		var angle = toDegrees(angleRadians) % 360;
+		var angle = toDegrees(angleRadians);
 		var hLimits = determineLimits(angle, pointPosition.x, textSize.w, 0, 180);
 		var vLimits = determineLimits(angle, pointPosition.y, textSize.h, 90, 270);
 
@@ -380,11 +380,11 @@ class RadialLinearScale extends LinearScaleBase {
 
 	getIndexAngle(index) {
 		var chart = this.chart;
-		var angleMultiplier = (Math.PI * 2) / chart.data.labels.length;
+		var angleMultiplier = Math.PI * 2 / chart.data.labels.length;
 		var options = chart.options || {};
 		var startAngle = options.startAngle || 0;
 
-		return index * angleMultiplier + helpers.toRadians(startAngle);
+		return _normalizeAngle(index * angleMultiplier + toRadians(startAngle));
 	}
 
 	getDistanceFromCenterForValue(value) {

test/fixtures/controller.polarArea/angle-lines.json

@@ -0,0 +1,35 @@
+{
+	"threshold": 0.05,
+    "config": {
+        "type": "polarArea",
+        "data": {
+            "labels": ["A", "B", "C", "D", "E"],
+            "datasets": [{
+                "data": [11, 16, 21, 7, 10],
+                "backgroundColor": [
+                    "rgba(255, 99, 132, 0.8)",
+                    "rgba(54, 162, 235, 0.8)",
+                    "rgba(255, 206, 86, 0.8)",
+                    "rgba(75, 192, 192, 0.8)",
+                    "rgba(153, 102, 255, 0.8)",
+                    "rgba(255, 159, 64, 0.8)"
+                ]
+            }]
+		},
+        "options": {
+            "responsive": false,
+            "legend": false,
+            "title": false,
+            "scale": {
+				"display": true,
+				"angleLines": {
+					"display": true,
+					"color": "#000"
+				},
+				"ticks": {
+					"display": false
+				}
+            }
+        }
+    }
+}

test/specs/scale.radialLinear.tests.js

@@ -535,7 +535,7 @@ describe('Test the radial linear scale', function() {
 			scale.ctx.getCalls().filter(function(x) {
 				return x.name === 'setTextAlign';
 			}).forEach(function(x, i) {
-				expect(x.args[0]).toBe(expected.textAlign[i]);
+				expect(x.args[0]).withContext('startAngle: ' + expected.startAngle + ', tick: ' + i).toBe(expected.textAlign[i]);
 			});
 
 			scale.ctx.getCalls().filter(function(x) {