Why does metadataVorbis#Composer and #Artist return a value that was unasked for?

[lychee]

I encountered this issue with my program alto where I was expecting the %artist% variable to return m.c["artist"], which is the actual artist field defined within the metadata, but it returned m.c["performer"] instead. Unbeknownst to me, I thought this was an error with my code, so after a few minutes of trial and error still yielded the same result. I was puzzled, but then decided to check Windows Explorer and said that the artist field was defined. I was confused at why it wasn't returning m.c["artist"] when Windows Explorer was, but that was when I finally decided to conclude my confusion by going directly to the source only to see the following code:

https://github.com/dhowden/tag/blob/master/vorbis.go#L175-L185

func (m *metadataVorbis) Artist() string {
	// PERFORMER
	// The artist(s) who performed the work. In classical music this would be the
	// conductor, orchestra, soloists. In an audio book it would be the actor who
	// did the reading. In popular music this is typically the same as the ARTIST
	// and is omitted.
	if m.c["performer"] != "" {
		return m.c["performer"]
	}
	return m.c["artist"]
}

It turned out that m.c["performer"] was " " which caused the library to return it instead.

ID3v1 and ID3v2 doesn't do this, so why does Vorbis? Metadata for each audio file varies, and when I call a method like Artist, I expect m.c["artist"], not m.c["performer"].

I was originally thinking about using Metadata#Raw() to mitigate this, but after seeing the note that says that it is an unstable mapping, which was expected, I couldn't risk instability for my program.

[Melvyn]

I have the same issue, this is very strange behavior that really shouldn't be there