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fix: merged ref behavior in react 19 #102

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fix: merged ref behavior in react 19 #102

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47 changes: 35 additions & 12 deletions src/useMergedRefs.ts
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Original file line number Diff line number Diff line change
@@ -1,22 +1,42 @@
import { useMemo } from 'react'
import { RefCallback, useMemo, version } from 'react'

const isReact19 = parseInt(version.split('.')[0]!, 10) >= 19

type CallbackRef<T> = (ref: T | null) => void
type Ref<T> = React.MutableRefObject<T> | CallbackRef<T>

function toFnRef<T>(ref?: Ref<T> | null) {
return !ref || typeof ref === 'function'
? ref
: (value: T | null) => {
ref.current = value as T
}
if (!ref || typeof ref === 'function') {
return ref
}

return (value: T | null) => {
ref.current = value as T
}
}

function cleanUp<T>(cleanup: unknown, ref: RefCallback<T> | null | undefined) {
if (typeof cleanup === 'function') {
cleanup()
} else if (ref) {
ref(null)
}
}

export function mergeRefs<T>(refA?: Ref<T> | null, refB?: Ref<T> | null) {
const a = toFnRef(refA)
const b = toFnRef(refB)
return (value: T | null) => {
if (a) a(value)
if (b) b(value)
const refASetter = toFnRef(refA)
const refBSetter = toFnRef(refB)

if (isReact19) {
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Does this need a react 19 check? Could it return the cleanup function regardless of version, which would be ignored in R18 and actually work in R19?

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I don't know. I think there are react warnings if you return stuff

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Ah ok - in that case, this code is missing the return handler for anything below R19

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ya but that is the same as now right? no return for < 19

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Sorry I meant the mergeRefs function. mergeRefs currently doesn't return a function on R18 and below

You meant to do this right?

export function mergeRefs<T>(refA?: Ref<T> | null, refB?: Ref<T> | null) {
  const refASetter = toFnRef(refA);
  const refBSetter = toFnRef(refB);

  return (value: T | null) => {
    const cleanupA = refASetter?.(value);
    const cleanupB = refBSetter?.(value);

    if (isReact19) {  // <--- This moved inside
      return () => {
        cleanUp(cleanupA, refASetter);
        cleanUp(cleanupB, refBSetter);
      };
    }
  };
}

return (value: T | null) => {
const cleanupA = refASetter?.(value)
const cleanupB = refBSetter?.(value)

return () => {
cleanUp(cleanupA, refASetter)
cleanUp(cleanupB, refBSetter)
}
}
}
}

Expand All @@ -36,7 +56,10 @@ export function mergeRefs<T>(refA?: Ref<T> | null, refB?: Ref<T> | null) {
* @param refB A Callback or mutable Ref
* @category refs
*/
function useMergedRefs<T>(refA?: Ref<T> | null, refB?: Ref<T> | null) {
function useMergedRefs<T>(
refA?: Ref<T | null> | null,
refB?: Ref<T | null> | null,
) {
return useMemo(() => mergeRefs(refA, refB), [refA, refB])
}

Expand Down
73 changes: 72 additions & 1 deletion test/useMergedRefs.test.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ import useMergedRefs from '../src/useMergedRefs.js'
import { render } from '@testing-library/react'

describe('useMergedRefs', () => {
it('should return a function that returns mount state', () => {
it('should work with forwardRef', () => {
let innerRef: HTMLButtonElement
const outerRef = React.createRef<HTMLButtonElement>()

Expand All @@ -18,9 +18,80 @@ describe('useMergedRefs', () => {
return <button ref={mergedRef} {...props} />
})

render(<Button ref={outerRef} />)

expect(innerRef!.tagName).toEqual('BUTTON')
expect(outerRef.current!.tagName).toEqual('BUTTON')
})

it('should work with plain function component', () => {
let innerRef: HTMLButtonElement
const outerRef = React.createRef<HTMLButtonElement>()

const Button = ({ ref }: { ref: React.Ref<HTMLButtonElement> }) => {
const [buttonEl, attachRef] = useCallbackRef<HTMLButtonElement>()
innerRef = buttonEl!

const mergedRef = useMergedRefs(ref, attachRef)

return <button ref={mergedRef} />
}

render(<Button ref={outerRef} />)

expect(innerRef!.tagName).toEqual('BUTTON')
expect(outerRef.current!.tagName).toEqual('BUTTON')
})

it('should call refs with null when unmounting', () => {
let innerRef: HTMLButtonElement | null = null

const outerRef = React.createRef<HTMLButtonElement>()

function Button({ ref }: { ref: React.Ref<HTMLButtonElement> }) {
const mergedRef = useMergedRefs(ref, (value) => {
innerRef = value
})

return <button ref={mergedRef} />
}

const result = render(<Button ref={outerRef} />)

expect(innerRef!.tagName).toEqual('BUTTON')
expect(outerRef.current!.tagName).toEqual('BUTTON')

result.unmount()

expect(innerRef).toBeNull()
expect(outerRef.current).toBeNull()
})

it('should call refs cleanup functions', () => {
let innerRef: HTMLButtonElement | null = null

const outerRef = React.createRef<HTMLButtonElement>()

function Button({ ref }: { ref: React.Ref<HTMLButtonElement> }) {
const mergedRef = useMergedRefs(ref, (value) => {
innerRef = value

return () => {
innerRef = 'hi' as any
}
})

return <button ref={mergedRef} />
}

const result = render(<Button ref={outerRef} />)

expect(innerRef!.tagName).toEqual('BUTTON')
expect(outerRef.current!.tagName).toEqual('BUTTON')

result.unmount()

expect(innerRef).toEqual('hi')
expect(outerRef.current).toBeNull()
})
})