refactor(vega): use useEffectEvent for VegaChart callbacks

[cixzhang]

What

Replace the onReady/onError ref-callback pattern in VegaChart with useEffectEvent.

Before, the callbacks were stashed in refs and reassigned every render so they could be read inside the View-lifecycle Effect without becoming dependencies:

const onReadyRef = useRef(onReady);
const onErrorRef = useRef(onError);
onReadyRef.current = onReady;
onErrorRef.current = onError;
// ...read as onReadyRef.current?.(view) inside useEffect

Now they're non-reactive Effect Events:

const onReady = useEffectEvent((view: View) => onReadyProp?.(view));
const onError = useEffectEvent((error: Error) => onErrorProp?.(error));
// ...called as onReady(view) inside useEffect

Behavior is identical: the callbacks always see the latest props, and passing fresh inline callbacks still never re-runs the effect or rebuilds the View. This just expresses the intent with the purpose-built primitive instead of manual ref bookkeeping.

Why only VegaChart?

useEffectEvent has a strict contract — an Effect Event may only be called from inside an Effect, never from an event handler, a useCallback, or during render. I audited every ref-callback site in the codebase against that rule:

Site	Callback invoked from	Fits useEffectEvent?
packages/vega/src/VegaChart.tsx	the View-lifecycle useEffect only	✅ converted here
Toast.tsx (onDismiss)	setTimeout reachable from focus/mouse handlers	❌ not effect-only
Outline/useScrollSpy.ts (onActiveIdChange)	Effect and the lockActiveId click handler	❌ mixed
Slider.tsx (onChangeEnd)	pointer/keyboard handlers	❌ event handler
hooks/useLongPress.ts (onLongPress)	touch handler (useCallback)	❌ event handler
Chat/useChatNewMessages.ts (onResize)	ResizeObserver in a useCallback	❌ not an effect
Table/.../useTableSortableState.tsx (onSortChange)	read during render, passed to another hook	❌ forbidden
Chat/useSpeechRecognition.ts, useChatDictation.ts (callbacksRef)	speech-recognition event handlers	❌ event handlers

Only VegaChart reads its ref callbacks exclusively inside an Effect, so it's the only place where useEffectEvent is correct rather than a rules-of-hooks violation. The other sites are legitimately using refs precisely because they fire from event handlers — converting them would trip the "only call from Effects" rule. Leaving them as-is is intentional.

Peer dependency bump

useEffectEvent is stable as of React 19.2. This raises @astryxdesign/vega's react/react-dom peer floor from >=19.0.0 to >=19.2.0. (@astryxdesign/vega is private / canary-only, so no changeset — the changeset gate rejects one for a non-releasable package.)

Testing

• pnpm -F @astryxdesign/vega typecheck ✓
• pnpm -F @astryxdesign/vega build ✓ (declaration emit)
• pnpm lint ✓ (repo checks + eslint; the 2 remaining warnings are pre-existing in unrelated files)
• No tests exist for the vega package; behavior is unchanged.

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Project	Deployment	Actions	Updated (UTC)
astryx	Error		Jul 9, 2026 11:16am

[josephfarina]

CI is red across build/lint/test/docsite-test/smoke-test, but it's all one root cause: the peerDependencies bump to react/react-dom >=19.2.0 wasn't reflected in the lockfile, so pnpm install --frozen-lockfile fails the frozen-lockfile check (lockfile still says >=19.0.0). A lockfile update should green everything.

The callback migration itself looks clean — onReady/onError go through useEffectEvent, the View lifecycle deps are unchanged, and the fail() path still wraps non-Errors. Note useEffectEvent is React 19.2+, which is why the peerDep bump is needed.

[cixzhang]

CI red