Fix skip-list edge cases with zero totals and negative values - #555
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- Return early from `find` when `total <= 0` to avoid crashes on empty lists - Clamp `targetValue` to >= 0 with `Math.max(0, targetValue)` after the `Math.min` call - Clamp `value` in `set` to >= 0 with `Math.max(0, value)` to prevent negative heights corrupting layout
Tests cover: - find() with zero total (all items have height 0) - find() with empty list (length 0) - find() with negative targetValue (clamped to 0) - find() with targetValue exceeding total (clamped to last item) - set() with negative value (clamped to 0) - set() with valid value (baseline behavior) Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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This was referenced Apr 10, 2026
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Summary
This PR fixes three edge cases in
vertical-collection/src/-private/data-view/skip-list.jsthat can cause crashes or corrupted layout state when item heights are zero or negative.Fix 1: Early return in
findwhentotal <= 0When a
SkipListis constructed with items that all have zero height (e.g. items not yet measured),totalwill be0. The previous code would proceed to computeMath.min(total - 1, targetValue)→Math.min(-1, targetValue), resulting in a negativetargetValuethat immediately triggers the assertiontargetValue must be greater than or equal to 0and throws.The fix returns
{ index: 0, totalBefore: 0, totalAfter: 0 }early whentotal <= 0, matching the same early-return pattern already used forlength === 0.Fix 2: Clamp
targetValueto >= 0Even after the
total <= 0guard, iftargetValueis negative (e.g. a negativescrollTopduring rubber-band scroll on iOS),Math.min(total - 1, targetValue)may still yield a negative value. AddingMath.max(0, targetValue)after theMath.minensures the value stays in bounds before the assertion.Fix 3: Clamp
valueinsetto >= 0When measuring item heights, a layout engine can occasionally return a negative or
-0value. Passing such a value tosettriggers the assertionvalue must non-negativeand throws, leaving the list in a partially-updated state. Clamping withMath.max(0, value)silently coerces bad measurements to0before the assertion, preventing corruption.Related issue: #208