fix(joint-react): tolerate a cell removed mid-render (useCell) and assign the forwarded ref during commit (useCombinedRef)

[samuelgja]

Description

Two independent React-hook lifecycle fixes in @joint/react, each with a jest repro. Both are reachable through ordinary, documented usage and both are masked by StrictMode's effect remount, so they only surfaced in production builds.

1. useCell — tolerate a cell removed mid-render (fixes #3442)

useCell() threw useCell(): no cell with id "X" and took the whole paper down when a subscribed cell was removed from a controlled cells array (renaming a node id is a remove + add). A renderElement subtree that subscribes to its own cell — directly, or via useMeasureElement -> useCell(selectElementSize) for any content-sized node, i.e. the default HTMLBox / SVGText renderers — re-runs its selector against the already-removed cell before <Paper> reconciles the removal, because the controlled apply fires that cell's per-id listener synchronously in a layout effect.

The wrapper selector now keeps the last value it resolved for the current id (one in-place-mutated ref, no per-render allocation) and returns it during that removed-mid-render window: the doomed subtree renders once more with stale data (equal to the cached value, so it does not even re-render) and unmounts on the next commit, instead of throwing. A cell that never resolved (genuine bad-id misuse / outside a render context) still throws.

Repro: use-cell-controlled-removal.test.tsx — a real Paper + subscribing renderElement doing a controlled b -> c rename crashes to 0 elements before the fix, survives (2 elements, no error) after.

2. useCombinedRef — assign the forwarded ref during commit, not in a passive effect (fixes #3444)

useCombinedRef assigned the forwarded ref inside a passive useEffect, one phase too late. React attaches refs during commit, before layout effects; a parent that reads the forwarded ref in its own useLayoutEffect saw null. useMeasureElement is exactly that consumer — it reads nodeRef.current in a layout effect, bails on null, and its dependency list does not change when the node is finally assigned, so a measured element stayed 0x0 in production.

The hook now returns a proxy whose setter forwards during commit (setForwardRef runs when React writes .current), keeping the RefObject .current read interface consumers depend on — which a plain callback ref could not.

Repro: use-combined-ref-timing.test.tsx (rendered with reactStrictMode: false) — a parent layout effect sees null before the fix, the node after.

Motivation and Context

The useCell crash came out of a Mermaid-to-JointJS renderer where every keystroke in a node id took the canvas down; the useCombinedRef one from an app measuring SVGText directly — correct under vite dev, every node a bare label with no shape or layout once built for production. StrictMode (on for every story and test) masks both, which is why the suite was blind to them.

Fixes #3442
Fixes #3444

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https://claude.ai/code/session_01F3YAR6SSWn39wTNhBTyFGX