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Is this a bug, or just a code refactoring without any effects on performance or behavior?

Is this a bug, or just a code refactoring without any effects on performance or behavior?

I didn't test it, but I think the RegExp and Bytes are all broken since #8446, because if (value && typeof value === 'object') { will be true for both, so the value saved in database will be a JSON-serialized version of mongodb.Bytes and mongodb.RegExp (or not broken if mapValues(restValue, transformInteriorValue) doesn't change the value of the object, but this is a coincidence instead of an explicit specified behavior).

Also this logic is handled properly after #9566, which is a definitely a behavior change (although it's from the original refactoring, but it never triggered since that):

// Handle update operators
  if (typeof restValue === 'object' && '__op' in restValue) {
    return transformUpdateOperator(restValue, true);
  }

Ok, we keep this classified as a bug. Could you please make sure the PR contains a test that demonstrates the issue?