Re-imports don't update data_source flex attr

[JOJ0]

Problem

When importing an album or a singleton that was previously imported already, the data_source flexible attribute is not updated. It stays as initially imported.

Setup

• OS: ---
• Python version: ---
• beets version: 1.6.1 dev-latest
• Turning off plugins made problem go away (yes/no): no

Proposed solution

data_source needs to be excluded in reimport_metadata()

[arsaboo]

Even album re-import does not update data_source.

[JOJ0]

Thanks for testing and clarifying. I was actually assuming that this is also the case but I wasn't sure yet. So, many thanks, that is very helpful! :-)

I'm pretty sure the problem is located here:

beets/beets/importer.py

Lines 810 to 812 in 4194914

	def reimport_metadata(self, lib):
	"""For reimports, preserves metadata for reimported items and
	albums.

On a reimport this function looks up what data_source is in the library already and then simply re-applies it. Similar to the ID fields over at PR #4708, data_source would need to be excluded from this "preserving mechanism".

We should investigate older issues and the one that implemented the reimport_metadata() method and make sure this is not "intentional" behaviour. If it was, I could think about making it configurable. As I see it now though, it feels like a bug, data_source is an informational field and after a reimport it is just wrong. I do use this field sometimes to save that "I tagged this manuall" with beet mod data_source=MANUAL query, but also then if I do find an appropriate album in some metadata source, it makes sense that this field gets overwritten and tells the truth.