fix(echarts): stop labeling zero-value segments in stacked bar charts

[bikash-barnwal]

SUMMARY

In a stacked Timeseries Bar chart with Values labels on, a series whose value is exactly 0 still rendered a label. A zero-value segment has no height, so its label is anchored to the same pixel as the neighboring segment's label and the two render on top of each other.

The mechanism is the threshold guard in transformSeries:

if (numericValue >= (thresholdValues[dataIndex] || Number.MIN_SAFE_INTEGER)) {

With percentage_threshold at its default of 0, extractDataTotalValues pushes a per-row threshold of 0 — which is falsy, so the guard degrades to numericValue >= Number.MIN_SAFE_INTEGER and admits everything, zeros included.

The fix returns an empty label for numericValue === 0 in that branch. It deliberately does not use > 0: negative stacked values render visible segments and are legitimately labeled today, so only the zero case — the one with nothing to anchor to — is suppressed. The guard sits after the !stack early return, so unstacked charts still label zeros as before. MixedTimeseries shares this code path and is fixed along with it.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Before: the zero series' 0 label sits on top of the adjacent segment's label.
After: no label is drawn for the zero-height segment; every other label is unchanged.

TESTING INSTRUCTIONS

cd superset-frontend
npm run test -- plugins/plugin-chart-echarts/test/Timeseries plugins/plugin-chart-echarts/test/MixedTimeseries

(295 tests across 17 suites pass, including the new case.)

Manually:

1. Build a Timeseries Bar chart with a dimension that produces a zero value for one series in a given bucket.
2. Set Stacked Style to Stack, enable Show Values, leave Percentage threshold at 0.
3. Before this change the zero series' label overlaps its neighbor's; after it, only visible segments carry labels.

ADDITIONAL INFORMATION

• Has associated issue: Fixes Timeseries Bar (stacked): zero-value series label overlaps the adjacent segment's label when percentage_threshold is 0 #42702
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

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Review Details

• Files reviewed - 2 · Commit Range: a2fd145..a2fd145

  • superset-frontend/plugins/plugin-chart-echarts/src/Timeseries/transformers.ts
  • superset-frontend/plugins/plugin-chart-echarts/test/Timeseries/transformers.test.ts
• Files skipped - 0
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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.70%. Comparing base (c068a8c) to head (a2fd145).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #43178   +/-   ##
=======================================
  Coverage   66.70%   66.70%           
=======================================
  Files        2872     2872           
  Lines      163447   163449    +2     
  Branches    37727    37728    +1     
=======================================
+ Hits       109024   109026    +2     
  Misses      52293    52293           
  Partials     2130     2130           

Flag	Coverage Δ
javascript	73.76% <100.00%> (+<0.01%)	⬆️

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