60 lines
2.3 KiB
JavaScript
Executable File
60 lines
2.3 KiB
JavaScript
Executable File
import { useCallback, useRef } from 'react';
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// This is a compatibility hook to support React 18 and 19 refs.
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// In 19, a cleanup function from refs may be returned.
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// In 18, returning a cleanup function creates a warning.
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// Since we take userspace refs, we don't know ahead of time if a cleanup function will be returned.
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// This implements cleanup functions with the old behavior in 18.
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// We know refs are always called alternating with `null` and then `T`.
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// So a call with `null` means we need to call the previous cleanup functions.
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export function useMergedRef(refA, refB) {
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const cleanupA = useRef(null);
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const cleanupB = useRef(null);
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// NOTE: In theory, we could skip the wrapping if only one of the refs is non-null.
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// (this happens often if the user doesn't pass a ref to Link/Form/Image)
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// But this can cause us to leak a cleanup-ref into user code (e.g. via `<Link legacyBehavior>`),
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// and the user might pass that ref into ref-merging library that doesn't support cleanup refs
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// (because it hasn't been updated for React 19)
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// which can then cause things to blow up, because a cleanup-returning ref gets called with `null`.
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// So in practice, it's safer to be defensive and always wrap the ref, even on React 19.
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return useCallback((current)=>{
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if (current === null) {
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const cleanupFnA = cleanupA.current;
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if (cleanupFnA) {
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cleanupA.current = null;
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cleanupFnA();
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}
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const cleanupFnB = cleanupB.current;
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if (cleanupFnB) {
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cleanupB.current = null;
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cleanupFnB();
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}
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} else {
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if (refA) {
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cleanupA.current = applyRef(refA, current);
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}
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if (refB) {
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cleanupB.current = applyRef(refB, current);
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}
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}
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}, [
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refA,
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refB
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]);
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}
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function applyRef(refA, current) {
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if (typeof refA === 'function') {
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const cleanup = refA(current);
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if (typeof cleanup === 'function') {
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return cleanup;
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} else {
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return ()=>refA(null);
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}
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} else {
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refA.current = current;
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return ()=>{
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refA.current = null;
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};
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}
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}
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//# sourceMappingURL=use-merged-ref.js.map
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