fix(Typeahead): omit aria-activedescendant when search results are empty (#4059)

[HelloOjasMutreja]

Summary

Fixes #4059.

When keyboard navigation (ArrowDown, Home) was used in a Typeahead with no matching search results, highlightedIndex was set to 0 and aria-activedescendant emitted an ID pointing to <listbox-id>-option-0. Because 0 option nodes exist in an empty results listbox, this left assistive technology with a dangling reference to a non-existent DOM element.

Root cause

1. In BaseTypeahead.tsx handleKeyDown, ArrowDown evaluated:
   setHighlightedIndex(prev => prev < results.length - 1 ? prev + 1 : 0)
   When results.length === 0, results.length - 1 is -1. -1 < -1 evaluated to false, causing highlightedIndex to evaluate to 0.
2. Home unconditionally set setHighlightedIndex(0).
3. aria-activedescendant checked popover.isOpen && highlightedIndex >= 0, which evaluated to true when highlightedIndex === 0 even though results.length === 0.

Fix

• BaseTypeahead.tsx:
  • Guarded ArrowDown, ArrowUp, Home, and End in handleKeyDown to only update highlight when results.length > 0.
  • Added strict bounds checking to aria-activedescendant: popover.isOpen && highlightedIndex >= 0 && highlightedIndex < results.length. Omits aria-activedescendant when results are empty.
  • Added bounds checking to the scrollIntoView effect (highlightedIndex < results.length).
  • Updated performSearch & performBootstrap to initialize highlight with shown.length > 0 ? 0 : -1 (the actual sliced results array).

Testing

• Added unit test in Typeahead.test.tsx verifying that aria-activedescendant is absent when search results are empty, and remains absent after pressing ArrowDown and Home.
• 43/43 tests in Typeahead.test.tsx pass.
• Full @astryxdesign/core package built cleanly (Babel + tsc + CSS + UMD).

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Project	Deployment	Actions	Updated (UTC)
astryx	Ready	Preview, Comment	Jul 25, 2026 5:55am

[github-actions]

PR Analysis Report

Modified Components

Typeahead

Metric	Before	After	Delta
Bundle Size (ESM)	N/A	N/A	N/A
Lines of Code	N/A	1107	-
Complexity	N/A	Very High (158)	-

Bundle Size Summary

Package	Size (ESM)	Size (CJS)	Gzipped
@astryxdesign/core	N/A	4.7KB	0B

Accessibility Audit

Status: No accessibility violations detected.

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[HelloOjasMutreja]

Technical Verification & Implementation Detail

• Capped results (searchResults.slice(0, maxMenuItems)) are stored in local shown scope to prevent setHighlightedIndex(0) from pointing to an index that exists in raw search results but is omitted from the rendered DOM listbox.
• aria-activedescendant explicitly checks highlightedIndex < results.length before emitting the item ID string, preventing screen readers from attempting to focus a non-existent option.
• Added bounds checks to useEffect scroll container listener and keyboard navigation guards (ArrowDown, ArrowUp, Home, End) when results.length === 0.