bugfix/16135-drillup-category-axis

samples/unit-tests/drilldown/drillup/demo.js

@@ -362,3 +362,57 @@ QUnit.test('Multi-level drilldown gets mixed  (#3579)', function (assert) {
         'The legend is not showing right information'
     );
 });
+
+QUnit.test(
+    'Drilldown on the chart with category axis and cropThreshold set, #16135.',
+    function (assert) {
+        const chart = Highcharts.chart('container', {
+            chart: {
+                type: 'column'
+            },
+            xAxis: {
+                type: 'category'
+            },
+            series: [{
+                keys: ['name', 'y', 'drilldown'],
+                cropThreshold: 5,
+                data: [
+                    ['A-0', 0, 'DrillSeries'],
+                    ['A-1', 1, 'DrillSeries'],
+                    ['A-2', 2, 'DrillSeries'],
+                    ['A-3', 3, 'DrillSeries'],
+                    ['A-4', 4, 'DrillSeries'],
+                    ['A-5', 5, 'DrillSeries'],
+                    ['A-6', 6, 'DrillSeries'],
+                    ['A-7', 7, 'DrillSeries'],
+                    ['A-8', 8, 'DrillSeries'],
+                    ['A-9', 9, 'DrillSeries']
+                ]
+            }],
+            drilldown: {
+                drilldown: {
+                    breadcrumbs: {
+                        showFullPath: false
+                    },
+                    series: [{
+                        data: [
+                            ['x-0', 1],
+                            ['x-1', 2],
+                            ['x-2', 3]
+                        ],
+                        name: 'DrillSeries',
+                        id: 'DrillSeries'
+                    }]
+                }
+            }
+        });
+
+        chart.series[0].points[1].doDrilldown();
+        chart.drillUp();
+        assert.strictEqual(
+            chart.series[0].xData[chart.series[0].xData.length - 1],
+            9,
+            `After drilling down and up on the chart with the category axis
+            the main series should go back to its original state.`
+        );
+    });

ts/Extensions/Drilldown.ts

@@ -988,6 +988,7 @@ Chart.prototype.drillUp = function (): void {
                 newSeries = addedSeries;
             }
         };
+    const drilldownLevelsNumber = (chart.drilldownLevels as any).length;
 
     while (i--) {
 
@@ -1013,6 +1014,16 @@ Chart.prototype.drillUp = function (): void {
             }
             oldSeries.xData = []; // Overcome problems with minRange (#2898)
 
+            // Reset the names to start new series from the beginning.
+            // Do it once to preserve names when multiple
+            // series are added for the same axis, #16135.
+            if (oldSeries.xAxis &&
+                oldSeries.xAxis.names &&
+                (drilldownLevelsNumber === 0 || i === drilldownLevelsNumber)
+            ) {
+                oldSeries.xAxis.names.length = 0;
+            }
+
             level.levelSeriesOptions.forEach(addSeries);
 
             fireEvent(chart, 'drillup', {