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Fix fastMerge not correctly merging all nested null values #518

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chrispader
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@chrispader chrispader commented Mar 25, 2024

@paultsimura

Details

Previously fastMerge wouldn't recursively call itself when merging an object with a target value of undefined or null. Therefore, nested null values wouldn't be removed either, because this only happens if we use fastMerge for nested keys and not set the value directly.

This PR fixes this issue, renames some variables for more clarity and adds comments to further explain the code.

It also adds 3 more unit tests, that @paultsimura suggested in #301 (comment) and #301 (comment).

Related Issues

#508

Automated Tests

Run the tests in fastMergeTests. I added an additional test that checks for exactly this issue.

Manual Tests

This was reported based on #490, so we might want to test if these changes (partially) fix the issues there.

Author Checklist

  • I linked the correct issue in the ### Related Issues section above
  • I wrote clear testing steps that cover the changes made in this PR
    • I added steps for local testing in the Tests section
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    • Android / native
    • Android / Chrome
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    • MacOS / Desktop
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Screenshots/Videos

Android: Native
Android: mWeb Chrome
iOS: Native
iOS: mWeb Safari
MacOS: Chrome / Safari
MacOS: Desktop

No screenshots, as this only internally affects Onyx operations.

@paultsimura
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@chrispader thanks for looking into this!
Could you please verify this fix doesn't reintroduce this issue? There was some talk about intentionally keeping nulls in cache during the mergeCollection.

@chrispader chrispader force-pushed the @chrispader/fix-nested-null-not-removed branch from 88b51ba to f738b16 Compare March 25, 2024 15:03
@chrispader chrispader force-pushed the @chrispader/fix-nested-null-not-removed branch from f738b16 to 2b402c1 Compare March 25, 2024 15:05
@chrispader
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This PR fixes only the problem in fastMerge, this doesn't fix the inconsistency between Onyx.merge and Onyx.mergeCollection.

Thinking about this, there might also be a discrepancy between Onyx.set and Onyx.multiSet. I'm gonna touch on that in another PR as well.

@chrispader
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@paultsimura i can't reproduce the issue from #408 (comment), so i think this PR should be ready for merge!

@chrispader chrispader marked this pull request as ready for review March 25, 2024 16:03
@chrispader chrispader requested a review from a team as a code owner March 25, 2024 16:03
@melvin-bot melvin-bot bot requested review from thienlnam and removed request for a team March 25, 2024 16:04
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@tgolen tgolen left a comment

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Thank you for the wonderful comments to explain why the logic is doing what it is.

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@thienlnam thienlnam left a comment

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Looks great, thanks!

@thienlnam thienlnam merged commit 3b6ad41 into Expensify:main Mar 25, 2024
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4 participants