fix: fixes #1876 for stack bar tooltips

packages/visx-xychart/src/components/series/private/BaseBarStack.tsx

@@ -91,9 +91,22 @@ function BaseBarStack<
     (
       params: NearestDatumArgs<XScale, YScale, BarStackDatum<XScale, YScale>>,
     ): NearestDatumReturnType<Datum> => {
-      const childData = seriesChildren.find((child) => child.props.dataKey === params.dataKey)
-        ?.props?.data;
-      return childData ? findNearestStackDatum(params, childData, horizontal) : null;
+      const childSeries = seriesChildren.find((child) => child.props.dataKey === params.dataKey);
+      const childData = childSeries?.props?.data;
+
+      const nearestDatum = childData
+        ? findNearestStackDatum(
+            params,
+            childData,
+            {
+              xAccessor: childSeries?.props?.xAccessor,
+              yAccessor: childSeries?.props?.yAccessor,
+            },
+            horizontal,
+          )
+        : null;
+
+      return nearestDatum;
     },
     [seriesChildren, horizontal],
   );

packages/visx-xychart/src/utils/findNearestStackDatum.ts

@@ -1,5 +1,6 @@
 import { AxisScale } from '@visx/axis';
 import { getFirstItem, getSecondItem } from '@visx/shape/lib/util/accessors';
+import { ScaleInput } from '@visx/scale';
 import findNearestDatumY from './findNearestDatumY';
 import findNearestDatumX from './findNearestDatumX';
 import { BarStackDatum, NearestDatumArgs } from '../types';
@@ -17,11 +18,19 @@ export default function findNearestStackDatum<
 >(
   nearestDatumArgs: NearestDatumArgs<XScale, YScale, BarStackDatum<XScale, YScale>>,
   seriesData: Datum[],
+  childAccessors: {
+    xAccessor: (d: Datum) => ScaleInput<XScale>;
+    yAccessor: (d: Datum) => ScaleInput<YScale>;
+  },
   horizontal?: boolean,
 ) {
   const { xScale, yScale, point } = nearestDatumArgs;
   const datum = (horizontal ? findNearestDatumY : findNearestDatumX)(nearestDatumArgs);
-  const seriesDatum = datum?.index == null ? null : seriesData[datum.index];
+  const stack = datum?.datum.data.stack;
+  const seriesDatum = seriesData.find((d) => {
+    const { yAccessor, xAccessor } = childAccessors;
+    return (horizontal ? yAccessor : xAccessor)(d) === stack;
+  });
 
   return datum && seriesDatum && point
     ? {

packages/visx-xychart/test/utils/findNearestDatum.test.ts

@@ -1,6 +1,7 @@
 import { AxisScale } from '@visx/axis';
 import { scaleBand, scaleLinear } from '@visx/scale';
 import { PositionScale } from '@visx/shape/lib/types';
+import { Point } from '@visx/point';
 
 import findNearestDatumX from '../../src/utils/findNearestDatumX';
 import findNearestDatumY from '../../src/utils/findNearestDatumY';
@@ -121,18 +122,32 @@ describe('findNearestStackDatum', () => {
   });
 
   it('should find the nearest datum', () => {
-    const d1 = { yVal: '🍌' };
-    const d2 = { yVal: '🚀' };
+    const d1 = { xVal: 0, yVal: '0' };
+    const d2 = { xVal: 8, yVal: '8' };
+
+    const stackData = [
+      { xy: [0, 0], item: { '0': 0, stack: '0' } },
+      { xy: [1, 1], item: { '8': 8, stack: '8' } },
+    ].map(({ xy, item }) => {
+      const dataItem = [...xy];
+      // @ts-ignore
+      dataItem.data = item;
+      return dataItem;
+    });
+
     expect(
       findNearestStackDatum(
         {
           ...params,
+          data: stackData,
+          point: new Point({ x: 0, y: 0 }),
           // type is not technically correct, but coerce for test
         } as unknown as NearestDatumArgs<AxisScale, AxisScale, BarStackDatum<AxisScale, AxisScale>>,
         [d1, d2],
+        { xAccessor: ({ xVal }) => xVal, yAccessor: ({ yVal }) => yVal },
         true,
       )!.datum,
-    ).toEqual(d2); // nearest datum index=1
+    ).toEqual(d1); // nearest datum index=0
   });
 });