fix: custom domain with fallback ordinal scale

src/chart_types/xy_chart/domains/x_domain.test.ts

@@ -470,24 +470,34 @@ describe('X Domain', () => {
       ],
     };
     const specDataSeries = [ds1, ds2];
+    const customDomain = {
+      min: 0,
+    };
 
     const { xValues } = getSplittedSeries(specDataSeries);
-    const mergedDomain = mergeXDomain(
+    const getResult = () => mergeXDomain(
       [
         {
           seriesType: SeriesTypes.Bar,
           xScaleType: ScaleType.Linear,
         },
         {
           seriesType: SeriesTypes.Bar,
-          xScaleType: ScaleType.Ordinal,
+          xScaleType: ScaleType.Linear,
         },
       ],
       xValues,
+      customDomain,
+      ScaleType.Ordinal,
     );
+
+    expect(getResult).not.toThrow();
+
+    const mergedDomain = getResult();
     expect(mergedDomain.domain).toEqual([0, 'a', 2, 5, 7]);
     expect(mergedDomain.scaleType).toEqual(ScaleType.Ordinal);
   });
+
   test('Should merge multi bar/line ordinal series correctly', () => {
     const ds1: BasicSeriesSpec = {
       chartType: ChartTypes.XYAxis,

src/chart_types/xy_chart/domains/x_domain.ts

@@ -60,7 +60,14 @@ export function mergeXDomain(
       if (Array.isArray(customXDomain)) {
         seriesXComputedDomains = customXDomain;
       } else {
-        throw new TypeError('xDomain for ordinal scale should be an array of values, not a DomainRange object');
+        if (fallbackScale === ScaleType.Ordinal) {
+          Logger.warn(`xDomain ignored for fallback ordinal scale. Options to resolve:
+
+1) Correct data to match ${mainXScaleType.scaleType} scale type (see previous warning)
+2) Change xScaleType to ordinal and set xDomain to Domain array`);
+        } else {
+          throw new TypeError('xDomain for ordinal scale should be an array of values, not a DomainRange object.');
+        }
       }
     }
   } else {

stories/scales/6_x_scale_fallback.tsx

@@ -0,0 +1,55 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import { boolean } from '@storybook/addon-knobs';
+import React from 'react';
+
+import { Axis, Chart, BarSeries, Position, ScaleType, Settings } from '../../src';
+
+export const Example = () => {
+  const includeString = boolean('include string is x data', true);
+  return (
+    <Chart className="story-chart">
+      <Settings xDomain={{ min: 0, max: 10 }} />
+      <Axis id="y" title="count" position={Position.Left} />
+      <Axis id="x" title={includeString ? 'ordinal fallback scale' : 'linear scale'} position={Position.Bottom} />
+      <BarSeries
+        id="bars"
+        name="amount"
+        xScaleType={ScaleType.Linear}
+        xAccessor="x"
+        yAccessors={['y']}
+        data={[
+          { x: 1, y: 390, val: 1222 },
+          { x: 2, y: 23, val: 1222 },
+          { x: includeString ? '3' : 3, y: 750, val: 1222 },
+          { x: 4, y: 854, val: 1222 },
+        ]}
+      />
+    </Chart>
+  );
+};
+
+Example.story = {
+  parameters: {
+    info: {
+      text: 'Using string values with a `Linear` scale will attempt to fallback to an `Ordinal` scale. Notice how the custom `xDomain` is ignored when the scale falls back to `Ordinal`.',
+    },
+  },
+};

stories/scales/scales.stories.tsx

@@ -31,3 +31,4 @@ export { Example as tooltipInLocalTimezone } from './2_local_tooltip';
 export { Example as tooltipInUTC } from './3_utc_tooltip';
 export { Example as specifiedTimezone } from './4_specified_timezone';
 export { Example as removeDuplicateAxis } from './5_remove_duplicates';
+export { Example as xScaleFallback } from './6_x_scale_fallback';