(re)allow modifying ticks in afterBuildTicks

docs/axes/README.md

@@ -31,7 +31,7 @@ There are a number of config callbacks that can be used to change parameters in
 | `beforeDataLimits` | `axis` | Callback that runs before data limits are determined.
 | `afterDataLimits` | `axis` | Callback that runs after data limits are determined.
 | `beforeBuildTicks` | `axis` | Callback that runs before ticks are created.
-| `afterBuildTicks` | `axis` | Callback that runs after ticks are created. Useful for filtering ticks.
+| `afterBuildTicks` | `axis`, `ticks` | Callback that runs after ticks are created. Useful for filtering ticks. Should return the filtered ticks.
 | `beforeTickToLabelConversion` | `axis` | Callback that runs before ticks are converted into strings.
 | `afterTickToLabelConversion` | `axis` | Callback that runs after ticks are converted into strings.
 | `beforeCalculateTickRotation` | `axis` | Callback that runs before tick rotation is determined.

src/core/core.scale.js

@@ -193,7 +193,8 @@ module.exports = Element.extend({
 		// we still support no return (`this.ticks` internally set by calling this method).
 		ticks = me.buildTicks() || [];
 
-		me.afterBuildTicks();
+		// Allow modification of ticks in callback.
+		ticks = me.afterBuildTicks(ticks) || ticks;
 
 		me.beforeTickToLabelConversion();
 
@@ -287,8 +288,15 @@ module.exports = Element.extend({
 		helpers.callback(this.options.beforeBuildTicks, [this]);
 	},
 	buildTicks: helpers.noop,
-	afterBuildTicks: function() {
-		helpers.callback(this.options.afterBuildTicks, [this]);
+	afterBuildTicks: function(ticks) {
+		var me = this;
+		// ticks is empty for old axis implementations here
+		if (helpers.isArray(ticks) && ticks.length) {
+			return helpers.callback(me.options.afterBuildTicks, [me, ticks]);
+		}
+		// Support old implementations (that modified `this.ticks` directly in buildTicks)
+		me.ticks = helpers.callback(me.options.afterBuildTicks, [me, me.ticks]) || me.ticks;
+		return ticks;
 	},
 
 	beforeTickToLabelConversion: function() {

test/specs/core.scale.tests.js

@@ -341,4 +341,99 @@ describe('Core.scale', function() {
 			});
 		});
 	});
+
+	describe('afterBuildTicks', function() {
+		it('should allow filtering of ticks', function() {
+			var labels = ['tick1', 'tick2', 'tick3', 'tick4', 'tick5'];
+			var chart = window.acquireChart({
+				type: 'line',
+				options: {
+					scales: {
+						xAxes: [{
+							id: 'x',
+							type: 'category',
+							labels: labels,
+							afterBuildTicks: function(axis, ticks) {
+								return ticks.slice(1);
+							}
+						}]
+					}
+				}
+			});
+
+			var scale = chart.scales.x;
+			expect(scale.ticks).toEqual(labels.slice(1));
+		});
+
+		it('should allow filtering of ticks (for new implementation of buildTicks)', function() {
+			var chart = window.acquireChart({
+				type: 'line',
+				data: {
+					labels: ['2016', '2017', '2018']
+				},
+				options: {
+					scales: {
+						xAxes: [{
+							id: 'x',
+							type: 'time',
+							time: {
+								parser: 'YYYY'
+							},
+							ticks: {
+								source: 'labels'
+							},
+							afterBuildTicks: function(axis, ticks) {
+								return ticks.slice(1);
+							}
+						}]
+					}
+				}
+			});
+
+			var scale = chart.scales.x;
+			expect(scale.ticks.length).toEqual(2);
+		});
+
+		it('should allow no return value from callback', function() {
+			var labels = ['tick1', 'tick2', 'tick3', 'tick4', 'tick5'];
+			var chart = window.acquireChart({
+				type: 'line',
+				options: {
+					scales: {
+						xAxes: [{
+							id: 'x',
+							type: 'category',
+							labels: labels,
+							afterBuildTicks: function() { }
+						}]
+					}
+				}
+			});
+
+			var scale = chart.scales.x;
+			expect(scale.ticks).toEqual(labels);
+		});
+
+		it('should allow empty ticks', function() {
+			var labels = ['tick1', 'tick2', 'tick3', 'tick4', 'tick5'];
+			var chart = window.acquireChart({
+				type: 'line',
+				options: {
+					scales: {
+						xAxes: [{
+							id: 'x',
+							type: 'category',
+							labels: labels,
+							afterBuildTicks: function() {
+								return [];
+							}
+						}]
+					}
+				}
+			});
+
+			var scale = chart.scales.x;
+			expect(scale.ticks.length).toBe(0);
+		});
+	});
 });