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bug(react): useAskableRegionCapture stale closure — onCapture/onCancel from previous start() call can fire #269
Description
Summary
In packages/react/src/useAskableRegionCapture.ts, the start() callback captures currentOptions in a closure and passes it to createAskableRegionCapture. If start() is called a second time before the first capture completes, the new call destroys the first handle — but any in-flight async callbacks from the destroyed handle still hold a reference to their currentOptions closure. Those callbacks will fire with the wrong options.
Root cause
const start = useCallback((overrides?) => {
handleRef.current?.destroy();
const currentOptions = { ...optionsRef.current, ...overrides };
const handle = createAskableRegionCapture(ctx, {
...currentOptions,
onCapture(packet, selection) {
// currentOptions is captured here
currentOptions.onCapture?.(packet, selection); // ← stale if start() was called again
},
onCancel() {
currentOptions.onCancel?.(); // ← stale
},
});
handleRef.current = handle;
handle.start();
}, [ctx]);Fix
Use a ref for callbacks so the latest version is always called:
const onCaptureRef = useRef(options.onCapture);
const onCancelRef = useRef(options.onCancel);
useEffect(() => {
onCaptureRef.current = options.onCapture;
onCancelRef.current = options.onCancel;
});
// In the capture setup:
onCapture: (packet, selection) => onCaptureRef.current?.(packet, selection),
onCancel: () => onCancelRef.current?.(),The same issue exists in useAskableTextSelectionCapture.ts and the Vue equivalent.
Impact
A rapid double-click on "start capture" or programmatic back-to-back starts can invoke the wrong callback, e.g. the old onCapture handler fires when the new capture completes.
Activity