Treat empty arrays as null in SET operations

[rafecolton]

Leaving in draft pending resolution of this discussion cc @tgolen @chuckdries @JS00001

Details

Treat empty array [] as null in SET operations to avoid poisoning cache due to bad data serialization in web layer. See this discussion.

Related Issues

https://github.com/Expensify/Expensify/issues/611769

Automated Tests

Added automated tests

Manual Tests

Commented out this block and this block and sent a mock expired transaction review webhook. Combined, that causes an SET to be called with [], and subsequent non-expired mock transactions are not displayed until the local cache is cleared. After applying the change, I confirmed that the subsequent non-expired transactions ARE displayed without explicitly clearing local cache.

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Screenshots/Videos

Android: Native

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

[JS00001]

Did we want to do the same for empty objects? Or just empty arrays?

[chuckdries]

The bad behavior we're concerned about here is

1. PHP parses empty JSON object as empty associative array
2. this SET update makes it to the client with [] as the value
3. client then rejects all future MERGE operations on the [] value because you can't merge into an array

This behavior does not happen if the value was {} to begin with, so it's not necessary here. Though I can see the argument that we might as well be consistent?

[JS00001]

Yeah my comment isnt for things breaking, but rather that IMO setting to {} should clear the entry, rather than do nothing. We prob dont need to store empty objects