Better property picking. Added a helper function so we don't have to write a complicated ternary everywhere. Updated tests accordingly.

src/controllers/controller.line.js

@@ -144,7 +144,7 @@
 				// Model
 				_model: {
 					// Appearance
-					tension: line.custom && line.custom.tension ? line.custom.tension : (this.getDataset().tension || this.chart.options.elements.line.tension),
+					tension: line.custom && line.custom.tension ? line.custom.tension : helpers.getValueOrDefault(this.getDataset().tension, this.chart.options.elements.line.tension),
 					backgroundColor: line.custom && line.custom.backgroundColor ? line.custom.backgroundColor : (this.getDataset().backgroundColor || this.chart.options.elements.line.backgroundColor),
 					borderWidth: line.custom && line.custom.borderWidth ? line.custom.borderWidth : (this.getDataset().borderWidth || this.chart.options.elements.line.borderWidth),
 					borderColor: line.custom && line.custom.borderColor ? line.custom.borderColor : (this.getDataset().borderColor || this.chart.options.elements.line.borderColor),
@@ -238,7 +238,7 @@
 					x: xScale.getPixelForValue(this.getDataset().data[index], index, this.index, this.chart.isCombo),
 					y: reset ? scaleBase : this.calculatePointY(this.getDataset().data[index], index, this.index, this.chart.isCombo),
 					// Appearance
-					tension: point.custom && point.custom.tension ? point.custom.tension : (this.getDataset().tension || this.chart.options.elements.line.tension),
+					tension: point.custom && point.custom.tension ? point.custom.tension : helpers.getValueOrDefault(this.getDataset().tension, this.chart.options.elements.line.tension),
 					radius: point.custom && point.custom.radius ? point.custom.radius : helpers.getValueAtIndexOrDefault(this.getDataset().radius, index, this.chart.options.elements.point.radius),
 					backgroundColor: this.getPointBackgroundColor(point, index),
 					borderColor: this.getPointBorderColor(point, index),

src/controllers/controller.radar.js

@@ -136,7 +136,7 @@
 				// Model
 				_model: {
 					// Appearance
-					tension: this.getDataset().tension || this.chart.options.elements.line.tension,
+					tension: helpers.getValueOrDefault(this.getDataset().tension, this.chart.options.elements.line.tension),
 					backgroundColor: this.getDataset().backgroundColor || this.chart.options.elements.line.backgroundColor,
 					borderWidth: this.getDataset().borderWidth || this.chart.options.elements.line.borderWidth,
 					borderColor: this.getDataset().borderColor || this.chart.options.elements.line.borderColor,
@@ -175,7 +175,7 @@
 					y: reset ? this.chart.scale.yCenter : pointPosition.y,
 
 					// Appearance
-					tension: point.custom && point.custom.tension ? point.custom.tension : this.chart.options.elements.line.tension,
+					tension: point.custom && point.custom.tension ? point.custom.tension : helpers.getValueOrDefault(this.getDataset().tension, this.chart.options.elements.line.tension),
 					radius: point.custom && point.custom.radius ? point.custom.pointRadius : helpers.getValueAtIndexOrDefault(this.getDataset().pointRadius, index, this.chart.options.elements.point.radius),
 					backgroundColor: point.custom && point.custom.backgroundColor ? point.custom.backgroundColor : helpers.getValueAtIndexOrDefault(this.getDataset().pointBackgroundColor, index, this.chart.options.elements.point.backgroundColor),
 					borderColor: point.custom && point.custom.borderColor ? point.custom.borderColor : helpers.getValueAtIndexOrDefault(this.getDataset().pointBorderColor, index, this.chart.options.elements.point.borderColor),

src/core/core.helpers.js

@@ -171,6 +171,9 @@
 
 			return value;
 		},
+		getValueOrDefault = helpers.getValueOrDefault = function(value, defaultValue) {
+			return value === undefined ? defaultValue : value;
+		},
 		indexOf = helpers.indexOf = function(arrayToSearch, item) {
 			if (Array.prototype.indexOf) {
 				return arrayToSearch.indexOf(item);

test/controller.line.tests.js

@@ -342,7 +342,7 @@ describe('Line controller tests', function() {
 		});
 
 		// Use dataset level styles for lines & points
-		chart.data.datasets[0].tension = 0.2;
+		chart.data.datasets[0].tension = 0;
 		chart.data.datasets[0].backgroundColor = 'rgb(98, 98, 98)';
 		chart.data.datasets[0].borderColor = 'rgb(8, 8, 8)';
 		chart.data.datasets[0].borderWidth = 0.55;
@@ -370,7 +370,7 @@ describe('Line controller tests', function() {
 			borderJoinStyle: 'miter',
 			borderWidth: 0.55,
 			fill: false,
-			tension: 0.2,
+			tension: 0,
 
 			scaleTop: 0,
 			scaleBottom: 200,
@@ -384,7 +384,7 @@ describe('Line controller tests', function() {
 			hitRadius: 3.3,
 			radius: 22,
 			skip: false,
-			tension: 0.2,
+			tension: 0,
 
 			// Point
 			x: 81,
@@ -393,8 +393,8 @@ describe('Line controller tests', function() {
 			// Control points
 			controlPointPreviousX: 81,
 			controlPointPreviousY: 62,
-			controlPointNextX: 91,
-			controlPointNextY: 52.6,
+			controlPointNextX: 81,
+			controlPointNextY: 62,
 		});
 
 		expect(chart.data.datasets[0].metaData[1]._model).toEqual({
@@ -404,17 +404,17 @@ describe('Line controller tests', function() {
 			hitRadius: 3.3,
 			radius: 22,
 			skip: false,
-			tension: 0.2,
+			tension: 0,
 
 			// Point
 			x: 131,
 			y: 15,
 
 			// Control points
-			controlPointPreviousX: 124.65778768378175,
-			controlPointPreviousY: 9.097346953222619,
-			controlPointNextX: 144.85778768378177,
-			controlPointNextY: 27.897346953222623,
+			controlPointPreviousX: 131,
+			controlPointPreviousY: 15,
+			controlPointNextX: 131,
+			controlPointNextY: 15,
 		});
 
 		expect(chart.data.datasets[0].metaData[2]._model).toEqual({
@@ -424,17 +424,17 @@ describe('Line controller tests', function() {
 			hitRadius: 3.3,
 			radius: 22,
 			skip: false,
-			tension: 0.2,
+			tension: 0,
 
 			// Point
 			x: 182,
 			y: 156,
 
 			// Control points
-			controlPointPreviousX: 167.76304506745115,
-			controlPointPreviousY: 130.76816898092827,
-			controlPointNextX: 187.96304506745116,
-			controlPointNextY: 166.56816898092828,
+			controlPointPreviousX: 182,
+			controlPointPreviousY: 156,
+			controlPointNextX: 182,
+			controlPointNextY: 156,
 		});
 
 		expect(chart.data.datasets[0].metaData[3]._model).toEqual({
@@ -444,15 +444,15 @@ describe('Line controller tests', function() {
 			hitRadius: 3.3,
 			radius: 22,
 			skip: false,
-			tension: 0.2,
+			tension: 0,
 
 			// Point
 			x: 232,
 			y: 194,
 
 			// Control points
-			controlPointPreviousX: 222,
-			controlPointPreviousY: 186.4,
+			controlPointPreviousX: 232,
+			controlPointPreviousY: 194,
 			controlPointNextX: 232,
 			controlPointNextY: 194,
 		});