That's an interesting suggestion! Which tags are you thinking of that produce None when the field is missing? We actually try to avoid that in most cases—the idea is to simplify client code so it doesn't need to constantly check the type of every field. For example, I believe artist is '', not None, when the underlying metadata is missing.

This design decision is certainly a trade-off. The simpler client code comes at the cost of not being able to distinguish the existence of tags.

Which tags are you thinking of that produce None when the field is missing?

Referencing #38 and #39, I thought this was the desired behavior if a tag is missing altogether.

Ah, you're totally right; I was thinking of the old behavior before we started making this change. (And also what we do at the beets layer, which is to coalesce missing values into default values.) In that case, this issue makes sense to me!