rusackas opened a new pull request, #41311:
URL: https://github.com/apache/superset/pull/41311
### SUMMARY
Fixes #21734
Prophet forecast confidence intervals appeared to "disappear" in the chart
tooltip whenever the forecast crossed zero. The root cause is in the ECharts
time-series forecast tooltip formatter
(`superset-frontend/plugins/plugin-chart-echarts/src/utils/forecast.ts`), which
used **truthiness** checks on the forecast values:
```ts
if (forecastTrend) { ... } // a trend of exactly 0 is skipped
if (forecastLower && forecastUpper) { } // a bound/height of 0 drops the
whole band
```
Because `0` is falsy in JS, a legitimate forecast trend of `0`, a lower
bound of `0`, or a zero-height band caused the corresponding values to be
silently omitted from the tooltip. This matches the report in #21734 ("if the
central estimate crosses 0, they are gone").
The fix switches these to explicit `typeof value === 'number'` checks — the
same pattern already used for the `observation` value just above — so zero
values are formatted and displayed like any other number.
Backend was already verified clean by the earlier test-only TDD guard
(#40141): the Prophet wrapper does not clamp at zero. This PR addresses the
remaining frontend rendering bug.
### BEFORE/AFTER
- **Before:** a forecast point with `ŷ = 0`, or a confidence bound of `0`,
rendered no trend/interval in the tooltip.
- **After:** `ŷ = 0` and intervals like `(0, 7)` or `(4, 4)` render
correctly.
### TESTING INSTRUCTIONS
```bash
cd superset-frontend
npx jest plugins/plugin-chart-echarts/test/utils/forecast.test.ts
```
Four new unit tests pin the zero-crossing behavior (trend = 0, lower = 0,
zero-height band, all-zero). They fail on `master` and pass with this change.
### ADDITIONAL INFORMATION
- [x] Has associated issue: Fixes #21734
- [ ] Required feature flags:
- [x] Changes UI (forecast tooltip rendering)
- [ ] Includes DB Migration
- [ ] Introduces new feature or API
- [ ] Removes existing feature or API
🤖 Generated with [Claude Code](https://claude.com/claude-code)
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