Respect min and max when building ticks (#4860)

Generate time scale ticks (`ticks.source: 'auto'`) based on the effective visualized range instead of the actual data range, meaning that the computed units and/or step size may change if the time options min and max are different from the data min and max.

Author: benmccann

src/scales/scale.time.js

@@ -504,8 +504,8 @@ module.exports = function(Chart) {
 			var me = this;
 			var chart = me.chart;
 			var timeOpts = me.options.time;
-			var min = parse(timeOpts.min, me) || MAX_INTEGER;
-			var max = parse(timeOpts.max, me) || MIN_INTEGER;
+			var min = MAX_INTEGER;
+			var max = MIN_INTEGER;
 			var timestamps = [];
 			var datasets = [];
 			var labels = [];
@@ -552,6 +552,9 @@ module.exports = function(Chart) {
 				max = Math.max(max, timestamps[timestamps.length - 1]);
 			}
 
+			min = parse(timeOpts.min, me) || min;
+			max = parse(timeOpts.max, me) || max;
+
 			// In case there is no valid min/max, let's use today limits
 			min = min === MAX_INTEGER ? +moment().startOf('day') : min;
 			max = max === MIN_INTEGER ? +moment().endOf('day') + 1 : max;

test/specs/scale.time.tests.js

@@ -376,23 +376,36 @@ describe('Time scale tests', function() {
 		var config;
 		beforeEach(function() {
 			config = Chart.helpers.clone(Chart.scaleService.getScaleDefaults('time'));
+			config.ticks.source = 'labels';
+			config.time.unit = 'day';
 		});
 
-		it('should use the min option', function() {
-			config.time.unit = 'day';
+		it('should use the min option when less than first label for building ticks', function() {
 			config.time.min = '2014-12-29T04:00:00';
 
 			var scale = createScale(mockData, config);
-			expect(scale.ticks[0]).toEqual('Dec 31');
+			expect(scale.ticks[0]).toEqual('Jan 1');
 		});
 
-		it('should use the max option', function() {
-			config.time.unit = 'day';
+		it('should use the min option when greater than first label for building ticks', function() {
+			config.time.min = '2015-01-02T04:00:00';
+
+			var scale = createScale(mockData, config);
+			expect(scale.ticks[0]).toEqual('Jan 2');
+		});
+
+		it('should use the max option when greater than last label for building ticks', function() {
 			config.time.max = '2015-01-05T06:00:00';
 
 			var scale = createScale(mockData, config);
+			expect(scale.ticks[scale.ticks.length - 1]).toEqual('Jan 3');
+		});
 
-			expect(scale.ticks[scale.ticks.length - 1]).toEqual('Jan 5');
+		it('should use the max option when less than last label for building ticks', function() {
+			config.time.max = '2015-01-02T23:00:00';
+
+			var scale = createScale(mockData, config);
+			expect(scale.ticks[scale.ticks.length - 1]).toEqual('Jan 2');
 		});
 	});