[Bug]: New SERIALIZABLE_PROPERTIES is only used by matcher-utils about jest HOT 4 OPEN

I think it makes sense to align, but I'll defer to @georgekaran

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Hey @stephenh

Your points make a lot of sense when it comes to the SERIALIZABLE_PROPERTIES. To be honest, maybe the name SERIALIZABLE_PROPERTIES wasn't the best choice 😅, which might have led to some confusion as it seems to imply a broader scope than it currently has.

That being said, I think we could go to either two directions:

• Rename this property to make it clear that is only used by the diff printer;
• Apply this same variable to equality checkers.

Personally the second option makes more sense to me, but is probably gonna take a lib bit more time than just a renaming.

Let me know what you guys think, so I can start working on a draft to address this issue and aim to include it in a future pull request.

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It seems the misunderstanding was here:

The name SERIALIZABLE_PROPERTIES to me infers it will be used "for serialization" which I would have expected to apply to both "the toEqual check" as well as "the toEqual diff", but also

Specifically, the "toEqual check". There is no serialization there; what is being compared is the runtime values. If it weren't for that, many values that are supposed to be different would pass as equals and vice-versa.

For example, a sparse array of length 2 (Array(2)) has the same value in all positions as an array of two undefined elements ([,,]), but those two don't serialize to the same thing ([ <2 empty items> ] vs [undefined, undefined]). This even happens in other cases like objectContaining, where the two objects being compared can be of different classes and, as such, will serialize differently while matching the test. The diff might show all the lines that are different, even though only a few of them might actually be causing the matcher to fail.

If the matcher was .serializesEquallyAs(other), then it would make sense to serialize the value for comparison.

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