Ignore invalid log scale min and max

Author: benmccann

src/scales/scale.logarithmic.js

@@ -174,8 +174,8 @@ module.exports = Scale.extend({
 		var DEFAULT_MIN = 1;
 		var DEFAULT_MAX = 10;
 
-		me.min = valueOrDefault(tickOpts.min, me.min);
-		me.max = valueOrDefault(tickOpts.max, me.max);
+		me.min = tickOpts.min >= 0 ? tickOpts.min : me.min;
+		me.max = tickOpts.max >= 0 ? tickOpts.max : me.max;
 
 		if (me.min === me.max) {
 			if (me.min !== 0 && me.min !== null) {
@@ -211,8 +211,8 @@ module.exports = Scale.extend({
 		var reverse = !me.isHorizontal();
 
 		var generationOptions = {
-			min: tickOpts.min,
-			max: tickOpts.max
+			min: tickOpts.min >= 0 ? tickOpts.min : undefined,
+			max: tickOpts.max >= 0 ? tickOpts.max : undefined
 		};
 		var ticks = me.ticks = generateTicks(generationOptions, me);
 

test/specs/scale.logarithmic.tests.js

@@ -477,6 +477,38 @@ describe('Logarithmic Scale tests', function() {
 		expect(yScale.ticks[tickCount - 1]).toBe(10);
 	});
 
+	it('should ignore invalid min and max options', function() {
+		var chart = window.acquireChart({
+			type: 'bar',
+			data: {
+				datasets: [{
+					data: [1, 1, 1, 2, 1, 0]
+				}],
+				labels: []
+			},
+			options: {
+				scales: {
+					yAxes: [{
+						id: 'yScale',
+						type: 'logarithmic',
+						ticks: {
+							min: -10,
+							max: -1010,
+							callback: function(value) {
+								return value;
+							}
+						}
+					}]
+				}
+			}
+		});
+
+		var yScale = chart.scales.yScale;
+		var tickCount = yScale.ticks.length;
+		expect(yScale.min).toBe(0);
+		expect(yScale.max).toBe(2);
+	});
+
 	it('should generate tick marks', function() {
 		var chart = window.acquireChart({
 			type: 'bar',