ComboboxProvider.selectItem and SelectProvider.selectItem were
structurally identical: both ran the same single/multi state machine
with allowDeselect semantics, the same resolve-DOM-element fallback,
and the same `commit-select`/`commit-unselect` event dispatch. The
only divergence: Combobox additionally syncs `inputValue` to the
selected label after the state mutation.
Extracts the shared logic into a new pure module
`src/uix/soma/layers/list-selection.ts`:
- `computeListSelection({ current, value, type, allowDeselect })`
→ `{ next, event, shouldClose, skipUpdate }`. Pure function, no
state writes, no DOM. The caller applies `next` to its own
`opts.value.current` after running any component-specific side
effects (Combobox: inputValue sync). `shouldClose`/`skipUpdate`
are decoupled so callers can compose their own order.
- `resolveListItemEl(root, itemAttr, value)` — DOM lookup helper
for the fallback event target. CSS.escape-safe.
Both providers now thin out to ~20 lines for selectItem (down from
~40-50). The single-mode no-op branch (re-select with deselect
disabled) and the early-return ordering are preserved exactly — close
fires once, value writes only when there's a real change.
Test result: 2393/2399 passing (2 extra from the new module's coverage,
6 same fails are Words + cookie infra).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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