refactor(plugin-chart-echarts): reuse finite-number guards in forecast tooltip

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

superset-frontend/plugins/plugin-chart-echarts/src/utils/forecast.ts

@@ -98,15 +98,24 @@ export const formatForecastTooltipSeries = ({
 }): string[] => {
   const name = `${marker}${sanitizeHtml(seriesName)}`;
   let value = typeof observation === 'number' ? formatter(observation) : '';
-  if (forecastTrend || forecastLower || forecastUpper) {
+  // Use finite-number checks rather than truthiness so that legitimate
+  // zero values (e.g. a forecast that crosses zero, or a confidence bound of
+  // exactly 0) are not dropped from the tooltip, while non-finite values
+  // (NaN/Infinity) are still excluded.
+  const isFiniteNumber = (val: number | undefined): val is number =>
+    typeof val === 'number' && Number.isFinite(val);
+  const hasTrend = isFiniteNumber(forecastTrend);
+  const hasLower = isFiniteNumber(forecastLower);
+  const hasUpper = isFiniteNumber(forecastUpper);
+  if (hasTrend || hasLower || hasUpper) {
     // forecast values take the form of "20, y = 30 (10, 40)"
     // where the first part is the observation, the second part is the forecast trend
     // and the third part is the lower and upper bounds
-    if (forecastTrend) {
+    if (hasTrend) {
       if (value) value += ', ';
       value += `ŷ = ${formatter(forecastTrend)}`;
     }
-    if (forecastLower && forecastUpper) {
+    if (hasLower && hasUpper) {
       if (value) value += ' ';
       // the lower bound needs to be added to the upper bound
       value += `(${formatter(forecastLower)}, ${formatter(

superset-frontend/plugins/plugin-chart-echarts/test/utils/forecast.test.ts

@@ -342,3 +342,72 @@ test('formatForecastTooltipSeries should format forecast with only confidence ba
     }),
   ).toEqual(['<img>qwerty', '(7, 15)']);
 });
+
+test('formatForecastTooltipSeries should show forecast trend equal to zero', () => {
+  expect(
+    formatForecastTooltipSeries({
+      seriesName: 'qwerty',
+      marker: '<img>',
+      observation: 10,
+      forecastTrend: 0,
+      forecastLower: 5,
+      forecastUpper: 7,
+      formatter,
+    }),
+  ).toEqual(['<img>qwerty', '10, ŷ = 0 (5, 12)']);
+});
+
+test('formatForecastTooltipSeries should show confidence band when lower bound is zero', () => {
+  expect(
+    formatForecastTooltipSeries({
+      seriesName: 'qwerty',
+      marker: '<img>',
+      observation: 10,
+      forecastTrend: 5,
+      forecastLower: 0,
+      forecastUpper: 7,
+      formatter,
+    }),
+  ).toEqual(['<img>qwerty', '10, ŷ = 5 (0, 7)']);
+});
+
+test('formatForecastTooltipSeries should show confidence band when band height is zero', () => {
+  expect(
+    formatForecastTooltipSeries({
+      seriesName: 'qwerty',
+      marker: '<img>',
+      observation: 10,
+      forecastTrend: 5,
+      forecastLower: 4,
+      forecastUpper: 0,
+      formatter,
+    }),
+  ).toEqual(['<img>qwerty', '10, ŷ = 5 (4, 4)']);
+});
+
+test('formatForecastTooltipSeries should show forecast trend and band all at zero', () => {
+  expect(
+    formatForecastTooltipSeries({
+      seriesName: 'qwerty',
+      marker: '<img>',
+      forecastTrend: 0,
+      forecastLower: 0,
+      forecastUpper: 0,
+      formatter,
+    }),
+  ).toEqual(['<img>qwerty', 'ŷ = 0 (0, 0)']);
+});
+
+test('formatForecastTooltipSeries should skip non-finite forecast values', () => {
+  expect(
+    formatForecastTooltipSeries({
+      seriesName: 'qwerty',
+      marker: '<img>',
+      observation: 10,
+      forecastTrend: NaN,
+      forecastLower: Infinity,
+      forecastUpper: -Infinity,
+      formatter,
+    }),
+  ).toEqual(['<img>qwerty', '10']);
+});