FA-53778 / Accessibility interaction semantics / Member archive

Cleared text attributes are serialized as null values · case 03

Cleared text attributes are serialized as null values.

Member previewVariant 3 · 3 implementations · 7 checks per implementation

Case contract

Input [length,default_attributes,spans] where spans are [start,end,attributes,priority]. Clamp endpoints to [0,length], discard empty/reversed spans. At each character position merge active spans over defaults by increasing priority, preserving input tie order; None attribute removes that attribute. Build maximal equal adjacent runs [start,end,attributes]. Zero length returns empty. Offsets are codepoints. Dictionary values are strings or None.

Why this case matters

Offline accessibility bridge model with explicit policy; useful for testing semantic API adapters independently of browser implementations.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
contract fixture 2	`[[0, 1, {"color": "red", "lang": null}], [1, 2, {"color": "blue", "lang": null}], [2, 3, {"color": "red", "lang": null}]]`	`[[0, 1, {"color": "red"}], [1, 2, {"color": "blue"}], [2, 3, {"color": "red"}]]`	Failed

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