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fix(useElementVisibility): Resolve possible issue with once watcher inside of callback #4723

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@jiwlee97 jiwlee97 commented Apr 23, 2025

Before submitting the PR, please make sure you do the following

  • Read the Contributing Guidelines.
  • Read the Pull Request Guidelines.
  • Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
  • Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
  • Ideally, include relevant tests that fail without this PR but pass with it.
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Description

fix #4704

Problem solved: The watchOnce call in useElementVisibility is happening inside of the intersection callback.
Solution: I moved the watchOnce call outside of the intersection callback to ensure it is only registered once when the composable is initialized.

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@dosubot dosubot bot added the size:M This PR changes 30-99 lines, ignoring generated files. label Apr 23, 2025
@ilyaliao
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So this is more of a structural optimization, right?

@jiwlee97
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So this is more of a structural optimization, right?

Yeah, it was a structural optimization.

@ilyaliao
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ilyaliao commented Apr 25, 2025

It looks good to me, but I'm not sure if this addresses the requirements described in #4704.

@jiwlee97
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jiwlee97 commented May 7, 2025

It looks good to me, but I'm not sure if this addresses the requirements described in #4704.

Thanks for the review!
From my understanding of the issue, the concern was that placing watchOnce inside the useIntersectionObserver callback might create a new watcher each time.
To fix that, I moved it outside so it only runs once in the expected scope.
Let me know if there’s anything I can clarify or improve further.

Comment on lines +39 to +48
vi.mock('../watchOnce', () => {
return {
watchOnce: vi.fn((source, callback) => {
// Immediately execute the callback if the source is true
if (typeof source === 'object' && source.value === true) {
callback(true)
}
}),
}
})
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why do we need to mock this? 🤔

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BUG | useElementVisibility | Possible issue with once watcher inside of callback
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