FA-38369 / Tree accessibility / Member archive

Visible tree range selection: Range union toggles previously selected descendants · case 04

Range union toggles previously selected descendants produces the wrong hierarchical widget state in a regression fixture.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Selectable rows are the ordered visible preorder supplied in rows; disabled rows cannot be selected. A hidden anchor falls back to focus. Preserve outside selections only for additive ranges. Report focus, anchor, ordered selection, and branch coverage.

Why this case matters

Offline executable model of a hierarchical accessibility interaction; inputs are bounded and valid as stipulated. No browser, assistive technology, or normative ARIA conformance is claimed.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
forward	`[[], "c5", "z", false]`	`[["z", "c0", "c2", "c3", "c4", "c5"], "c5", "z", true]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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