Changes multimap entries Iterable to make a deep copy of pending adds and deletes

[acrites]

Updates multimap entries iterable to make a deep copy of pending adds and deletes. ImmutableMap.copyOf does not. This was causing testMultimapEntries validates runner test to fail since the iterators created were no longer a snapshot of the current state at the time the Iterable was made.

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Summary of Changes

Hello @acrites, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a critical bug within the MultimapUserState class where iterators returned by the entries() method did not accurately represent a snapshot of the state at the time of their creation. The issue stemmed from the use of ImmutableMap.copyOf and ImmutableSet.copyOf, which perform shallow copies, allowing subsequent modifications to the underlying pendingAdds and pendingRemoves collections to affect existing iterators. The fix involves replacing these shallow copies with explicit deep copy mechanisms, ensuring that all iterators provide a consistent and immutable view of the state, thereby preventing unexpected behavior and addressing a specific test failure.

Highlights

• Deep Copy for Pending Adds: The entries() method in MultimapUserState now explicitly creates a deep copy of the pendingAdds map, ensuring that iterators reflect a true snapshot of the state at the time of creation.
• Deep Copy for Pending Removes: Similarly, a deep copy is now performed for the pendingRemoves set, preventing mutations to the underlying collection from affecting previously created iterators.
• Bug Fix: This change resolves an issue where ImmutableMap.copyOf and ImmutableSet.copyOf were not providing deep copies, which caused the testMultimapEntries runner test to fail due to inconsistent iterator states.

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[acrites]

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[kennknowles]

Calling this a "deep copy" is still inaccurate, since it is now a "slightly deeper copy" that still stores pointers. I'm surprised this has any effect at all, actually. Approving on faith, if it makes tests go green. But I don't really understand it.

[kennknowles]

OK I read really deep in Guava code and it does look like it will eventually build a Map that is backed by the literal same entry array as the input. Makes you think copyOf and Immutable don't mean what you think they mean...