Merge pull request #4553 from VisActor/fix/sankey-tooltip-source-zero

fix: preserve Sankey tooltip titles for zero-index source links

Author: xuefei1313

common/changes/@visactor/vchart/fix-sankey-tooltip-source-zero_2026-04-13-09-39.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "comment": "fix: handle sankey tooltip labels when source index is 0 (Issue #4488)",
+      "type": "patch",
+      "packageName": "@visactor/vchart"
+    }
+  ],
+  "packageName": "@visactor/vchart",
+  "email": "lixuef1313@163.com"
+}

packages/vchart/__tests__/unit/series/sankey.test.ts

@@ -0,0 +1,38 @@
+import { SankeySeriesTooltipHelper } from '../../../src/series/sankey/tooltip-helper';
+
+const createMockSeries = () =>
+  ({
+    id: 'sankey-series',
+    type: 'sankey',
+    getSpec: () => ({
+      categoryField: 'nodeName'
+    }),
+    getSeriesField: () => 'nodeName',
+    getSeriesKeys: () => ["Agricultural 'waste'", 'Bio-conversion', 'CCCCC', 'DDD'],
+    getDimensionField: () => ['nodeName'],
+    getMeasureField: () => ['value'],
+    getSeriesStyle:
+      (): any =>
+      (_: string): any =>
+        undefined,
+    getDefaultShapeType: () => 'square'
+  } as any);
+
+describe('[Series-Sankey] tooltip helper', () => {
+  test('should resolve link title when source is 0', () => {
+    const helper = new SankeySeriesTooltipHelper(createMockSeries());
+
+    expect(
+      helper.dimensionTooltipTitleCallback({
+        source: 0,
+        target: 2,
+        value: 124.729,
+        datum: {
+          source: 0,
+          target: 2,
+          value: 124.729
+        }
+      } as any)
+    ).toBe("Agricultural 'waste' => CCCCC");
+  });
+});

packages/vchart/src/series/sankey/tooltip-helper.ts

@@ -1,11 +1,11 @@
 import type { ISeriesTooltipHelper } from '../interface';
 import { BaseSeriesTooltipHelper } from '../base/tooltip-helper';
-import { isNumber } from '@visactor/vutils';
+import { isNil, isNumber } from '@visactor/vutils';
 import type { Datum } from '../../typings/common';
 
 export class SankeySeriesTooltipHelper extends BaseSeriesTooltipHelper implements ISeriesTooltipHelper {
   protected _getDimensionData = (datum: any) => {
-    if (datum.source) {
+    if (!isNil(datum?.source) && !isNil(datum?.target)) {
       if (isNumber(datum.source)) {
         const seriesKeys = this.series.getSeriesKeys();
         return seriesKeys[datum.source] + ' => ' + seriesKeys[datum.target];