feat: bubble functional state updaters through lift

[megheaiulian]

Problem

When lift is used to delegate property ownership to a parent component, rapid-fire calls to useProperty's setter with functional updaters produce incorrect state. Each call reads stale host[property] because lift's preventDefault() blocks the local write, and the parent hasn't re-rendered yet. See #149 for full analysis.

Solution

Notify first, compute after. If defaultPrevented (i.e., lift intercepted), skip the local write. If not prevented, commit the resolved value.

Bubble the original updater function in ev.detail.updater so lift can pass it to the parent's setter. The parent's setter is itself a useProperty updater that calls resolve() against its own host[property] — the authoritative state. Meanwhile, ev.detail.value always contains the locally-resolved value for backward compatibility with non-lift listeners.

Method breakdown

Method	Responsibility
resolve(valueOrUpdater)	Given a value or updater function, compute [previousValue, value, updater]. Resolves functions against host[property].
notify(value, updater?)	Dispatch event with { value, updater, path } in detail. value is always the resolved value. Returns event.
updater(valueOrUpdater)	Orchestrate: resolve → notify → if prevented return → dedup+write. Called from constructor for init and at runtime.

updateProp, init, and commit removed — replaced by resolve + notify + inline dedup/write.

Event detail

ev.detail now always contains:

• value: the resolved value (computed against host[property]). Always present, never undefined.
• updater: the original updater function for functional calls, undefined for direct values. Used by lift to resolve against parent state.
• path: unchanged.

Flow for rapid-fire calls with lift

select(item1) → updater((sel) => [...sel, item1])
  → resolve: previousValue=[], value=[item1], updater=fn
  → notify({ value: [item1], updater: fn })
  → lift: ev.preventDefault(), setter(fn)
  → parent updater: resolve against parentHost.selectedItems=[] → value=[item1]
  → parent notify → not prevented → write parentHost.selectedItems=[item1]
  → child: defaultPrevented, return (no local write)

select(item2) → updater((sel) => [...sel, item2])
  → resolve: previousValue=[] (stale), value=[item2], updater=fn
  → notify({ value: [item2], updater: fn })
  → lift: setter(fn)
  → parent updater: resolve against parentHost.selectedItems=[item1] → value=[item1, item2]
  → parent notify → not prevented → write parentHost.selectedItems=[item1, item2]
  → child: defaultPrevented, return

Each call resolves correctly at the parent level because lift passes the updater function, not the locally-resolved value.

Backward Compatibility

• ev.detail.value: always the resolved value. Previously was the resolved value for direct calls only. Non-lift listeners that read ev.detail.value get correct values for both direct and functional updaters.
• ev.detail.updater: new optional field — only used by lift.
• ev.detail.path: unchanged.

Breaking changes

• useProperty.updateProp removed (was internal, not part of public API)
• useProperty.init removed (was internal, not part of public API)
• Event detail shape now includes updater field alongside value
• ev.detail.value is always the resolved value (was undefined for functional updaters)
• lift now passes ev.detail.updater ?? ev.detail.value to setter (was ev.detail.value)
• useProperty setter now always dispatches a change event, even if the value is unchanged

Tests

94 tests passing (89 existing + 5 new):

• "event detail contains updater for functional calls" — verifies ev.detail.value is resolved (9, not undefined) and ev.detail.updater is the function
• "event detail contains value for direct calls" — verifies ev.detail.value is the value and ev.detail.updater is undefined
• "lift bubbles functional updater to parent" — child calls functional setter, parent lift intercepts
• "rapid-fire functional updaters with lift accumulate correctly" — 3 synchronous setItems((items) => [...items, x]) calls produce a,b,c
• "lift with direct value still works" — direct values still work with lift

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Latest commit: aaa59cb

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[cristinecula]

Good catch!