fix(plugin-chart-echarts): omit stacked value labels on zero-height segments

[MannXo]

SUMMARY

Fixes #42702.

On a stacked echarts_timeseries_bar with "Show Value" on and "Only Total" off, a series whose value is 0 for a category still gets a value label. A zero-height stacked segment begins and ends at the same coordinate as the top of the segment beneath it, so echarts draws that label on top of the label belonging to the segment below, and the two numbers render over each other as unreadable text.

This adds one guard: a stacked segment with no height carries no label.

One correction to the root cause in the issue. The issue reports that with the default percentage_threshold: 0 the condition becomes numericValue >= 0. It does not. 0 is falsy, so thresholdValues[dataIndex] || Number.MIN_SAFE_INTEGER evaluates to Number.MIN_SAFE_INTEGER and the condition is numericValue >= Number.MIN_SAFE_INTEGER, which is true for everything. Observed against the label formatter:

thresholdValues=[0]     0 -> "0"     -5 -> "-5"     32 -> "32"
thresholdValues=[10]    0 -> ""       5 -> ""       50 -> "50"

If the mechanism were >= 0, that -5 would have been dropped. So the || is doing its job: a 0 threshold means "no threshold filtering", and a real threshold already suppresses zeros. That makes this a label-collision bug rather than a threshold bug, and it is why the fix does not touch the threshold expression. Rewriting that comparison would change threshold semantics for every user and would suppress legitimate negative labels.

A second defect on the same code path. A null value renders the literal string "null" as a chart label, with the production number formatter:

0 -> "0"     null -> "null"     32 -> "32"     -5 -> "-5"

A null segment has no height either, so it collides identically. The guard covers both under one rule rather than special-casing zero.

Prior art in this plugin. Timeseries/transformProps.ts already omits zero observations from the rich tooltip of a stacked series (if (value.observation === 0 && stack) return;). This applies the same judgement to the per-series value label.

Scope: stacked series only. Unstacked labels sit on the bar itself with nothing to collide with, and they return earlier in the formatter. Only-total labels render the stack total and are unaffected. The stack && clause is deliberate for legibility even though the earlier !stack return makes it defensive rather than load-bearing, matching how the tooltip guard above spells out the same condition.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Stacked bar, two metrics, "Show Value" on, "Only Total" off, default percentage threshold, with the upper series at 0 for two categories.

Before	After

The label coordinates from the rendered SVG, so the images and the numbers agree:

before                              after
x=146.3 y=143.0 '0'                 x=146.3 y=143.0 '32'
x=146.3 y=143.0 '32'                x=775.2 y=179.2 '27'
x=775.2 y=179.2 '0'
x=775.2 y=179.2 '27'

overlapping pairs: ('0','32'), ('0','27')       overlapping pairs: none

TESTING INSTRUCTIONS

Manual:

1. Create an echarts_timeseries_bar chart with two metrics, for example A and B.
2. Set Stacked, turn on "Show Value", leave "Only Total" off and "Percentage threshold" at its default.
3. Include a category where the metric stacked on top is 0 and the one below it is not, for example {"category": "1-3g", "B": 32, "A": 0}.
4. Run the chart. Before this change the 0 label is drawn over the 32 label as doubled text. After it, only 32 is labelled.
5. Confirm the unchanged cases: a category where both metrics are non-zero still labels both segments; switching off Stacked still labels a 0; turning on "Only Total" still shows the stack total.

Automated, in plugins/plugin-chart-echarts/test/Timeseries/transformers.test.ts:

npx jest plugins/plugin-chart-echarts/test/Timeseries/transformers.test.ts

Five cases cover zero and null suppressed when stacked, non-zero and negative kept, zero kept when not stacked, percentage_threshold still filtering below-threshold values, and only-total labels unchanged.

Gates run locally on Node 24.16.0, using the commands from .github/workflows/superset-frontend.yml:

npx jest plugins/plugin-chart-echarts     69 suites, 772 tests, all passing
npm run lint                              clean
npm run plugins:build && npm run type     clean
npm ls --all --package-lock-only --depth=0    clean
pre-commit run --files <the two changed files>   all hooks passing

Each new assertion was checked by reverting the behaviour it covers and confirming the intended test fails: removing the guard fails the zero-height case, and guarding zero without null fails it too. One further sabotage, removing the stack && clause, is not caught, because the !stack branch returns before the guard is reached, so no test can distinguish it. Noting that rather than presenting the set as complete.

ADDITIONAL INFORMATION

• Has associated issue: 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

[bito-code-review]

Code Review Agent Run #5e26f6

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Review Details

• Files reviewed - 2 · Commit Range: 20b8ee2..20b8ee2

  • 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 65.59%. Comparing base (e66c7fc) to head (20b8ee2).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #42756      +/-   ##
==========================================
- Coverage   65.59%   65.59%   -0.01%     
==========================================
  Files        2819     2819              
  Lines      160166   160168       +2     
  Branches    36569    36570       +1     
==========================================
- Hits       105059   105055       -4     
- Misses      53059    53065       +6     
  Partials     2048     2048              

Flag	Coverage Δ
javascript	71.74% <100.00%> (-0.01%)	⬇️

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