fix(mixed-timeseries): stop duplicating first metric in multi-metric + group-by series names (#40146)

Co-authored-by: Claude Code <noreply@anthropic.com>

superset-frontend/plugins/plugin-chart-echarts/test/MixedTimeseries/transformProps.test.ts

@@ -1161,3 +1161,83 @@ test('x-axis dedup keeps the forced min label when the endpoints format identica
 
   expect(formatter(min)).toBe('May');
 });
+
+test('regression #37921: multi-metric Query A with groupby does not duplicate first metric in series names', () => {
+  // Regression test for https://github.com/apache/superset/issues/37921
+  // ("Residual" follow-up to #37055).
+  //
+  // When Query A has multiple metrics + at least one Group By dimension,
+  // the display-name builder in transformProps.ts used to prepend the FIRST
+  // metric's display name to every series that didn't literally contain it:
+  //   name: `${MetricDisplayNameA}, ${entryName}`
+  // For series belonging to the *second* metric, this produced a
+  // cross-contaminated label like `score_one, score_two, A` — the
+  // user-visible "first metric duplicated" symptom in the legend / tooltip.
+  // The fix derives each series' metric from its label-map tuple instead.
+  const multiMetricRows = [
+    {
+      'score_one, A': 1,
+      'score_one, B': 2,
+      'score_two, A': 3,
+      'score_two, B': 4,
+      ds: 599616000000,
+    },
+    {
+      'score_one, A': 5,
+      'score_one, B': 6,
+      'score_two, A': 7,
+      'score_two, B': 8,
+      ds: 599916000000,
+    },
+  ];
+  const multiMetricLabelMap = {
+    ds: ['ds'],
+    'score_one, A': ['score_one', 'A'],
+    'score_one, B': ['score_one', 'B'],
+    'score_two, A': ['score_two', 'A'],
+    'score_two, B': ['score_two', 'B'],
+  };
+
+  const queryAData = createTestQueryData(multiMetricRows, {
+    label_map: multiMetricLabelMap,
+  });
+  // Query B keeps the existing single-metric shape — the bug is on
+  // Query A's path so we just need a valid Query B alongside.
+  const queryBData = createTestQueryData(defaultQueryRows, {
+    label_map: defaultLabelMap,
+  });
+
+  const chartProps = createEchartsTimeseriesTestChartProps<
+    EchartsMixedTimeseriesFormData,
+    EchartsMixedTimeseriesProps
+  >({
+    ...MIXED_TIMESERIES_CHART_PROPS_DEFAULTS,
+    defaultQueriesData: [queryAData, queryBData],
+    formData: {
+      ...formData,
+      metrics: ['score_one', 'score_two'],
+      groupby: ['category'],
+    },
+    queriesData: [queryAData, queryBData],
+  });
+  const transformed = transformProps(chartProps);
+
+  const queryASeriesNames = (transformed.echartOptions.series as any[])
+    .map((s: any) => String(s.name))
+    .filter((n: string) => n.includes('score_'));
+
+  // Each (metric, dim_value) combo from Query A should appear exactly once
+  // with the *correct* metric prefix — not the first-metric-prepended-to-
+  // everything-else form. Comparing the sorted array (rather than using
+  // separate toContain assertions) also catches a regression that emits
+  // duplicate series for the same name.
+  expect([...queryASeriesNames].sort()).toEqual(
+    ['score_one, A', 'score_one, B', 'score_two, A', 'score_two, B'].sort(),
+  );
+
+  // And explicitly: no series name should contain *both* metric names —
+  // that's the smoking gun for the duplication bug.
+  for (const name of queryASeriesNames) {
+    expect(name).not.toMatch(/score_one,\s+score_two/);
+  }
+});