[DaveBlake]

Many balls in the air....

Looking at #3 of the OP, the questions from http://forum.kodi.tv/showthread.php?tid=...pid2590360, and chatting with @night199uk on Slack I think I have an idea about a way forwards.

Reminder:

3) if the 'prefer online info' setting is enabled, and 'show song and album artists' is enabled:
this causes the same artist being listed twice in your library if the artistname in your tags does not 100% match the artistname the scraper returns.

for instance "The B-52's" vs. "The B-52s":
3.1) i have all songs of an album tagged with artist "The B-52's"
3.2) we start the album scanner and it returns the mbid for this artist
3.3) we pass this mbid to the artist scraper and it returns info for "The B-52s" and kodi adds it to the db.
3.4) kodi now scans all songs for 'additional' artists. it finds "The B-52's" and checks if it's already in the db... nope
3.5) we pass "The B-52's" to the artist scraper and it returns info for whatever closest match it can find and kodi adds this artist to the db

ref: https://github.com/xbmc/xbmc/blob/99c25f...#L843-L883

The current merge of album artist(s) when "prefer online info" is enabled is flawed. The artist data derived from tags is only partialy overwritten, and with storing/using scraped MBIDs it gets even more messy. The original idea was for everything in the library to have MBIDs from tags, and then use scraping with "prefer online info" to fetch the lastest info from MB including if the artist credits had been changed. To do that correctly the merge process needs extending to cover song artists too.

But I don't think we can sensibly do that for items where we lookup by name only and thus scrape the MBID, with possible inaccuracies and partial results due to 503 timeouts etc.. Sure we can fetch info like dates, bio, styles etc. and artwork, but overwriting the artist credits is too big an impact.

A "my tagging is a mess, build me a library" facility will need some kind of acoustic fingerprint approach, lookup on names alone isn't it. Meanwhile people can use Picard, and if that can't tag their music accurately with MBID then Kodi isn't going to be able to identify the MBIDs by scraping.

So the solution, is either a rework of "prefer online info" into 2 settings:
a) one to overwrite artist or album data (but not the album artist credits) derived from tags with that scraped (from online or NFO);

b)the other to indicate that music tagged with MBID can have the artist credits for both albums and songs updated, including the artist names, updated based on the MBID tags, ignoring what other tag values e.g. artist, albumartist etc. may say.

EDIT: or when "prefer online info" is enabled AND we have MBIDs from tags, then it causes the artists credits to be updated.

May try to add this, along with 503 retries, to PR12120