feat(a11y): fallback <desc> generators for core charts (#119)#129
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Surface already wires role/title/desc/aria-label; the gap was that charts only emitted <desc> when the consumer passed `description`. Adds per-chart-type fallback generators so screen-reader users get a useful one-liner from the data when no description is provided. - new src/core/a11yDescribe.ts: describeBars / describeSeries / describePie / describeScatter - BarChart, LineChart, AreaChart, PieChart, ScatterPlot fall back to the generator when `description` is omitted - new src/components/a11y.test.ts covers role=img, fallback <desc>, explicit-description precedence, and aria-label falling back to title - a11yDescribe.test.ts covers each generator (singular nouns, empty data, multi-series, decimal formatting) Bundle stays at 48 KB gzipped (budget 75 KB). All 395 existing tests pass plus 17 new. Follow-up tracked in #119: dataTable forwarding through diagrams (custom DataTableModel per diagram type).
This was referenced May 28, 2026
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Summary
src/core/a11yDescribe.tswithdescribeBars/describeSeries/describePie/describeScatter— short, deterministic, dependency-free sentences summarising chart shape.descriptionis omitted, so the<desc>tag always carries something useful for screen readers.src/components/a11y.test.tscoversrole="img", fallback<desc>, explicit-description precedence, andaria-labelfalling back totitle.a11yDescribe.test.tscovers each generator (singular nouns, empty data, multi-series, decimal trimming).Why this is narrower than the issue
The original #119 spec assumed a11y plumbing was missing. Audit showed
Surfacealready wiresrole/<title>/<desc>/aria-label/ SR-only data table, and 14 of 15 chart components forward those props. The real remaining gap was: no fallback<desc>when consumers don't passdescription, and no a11y test coverage. This PR closes both.I narrowed the issue body before this PR;
dataTableforwarding through diagrams (customDataTableModelper diagram type) is now the follow-up tracked there.Verification
npm run typecheckcleannpm test— 395 existing tests pass + 17 newnpm run build && npm run check:bundle— browser entry 48 KB gzipped (budget 75 KB), no font leakTest plan
Closes the narrowed scope of #119.