fix(fetchart): sources definition

[ShimmerGlass]

Description

The fetchart plugin would silently drop unknown sources defined in config, leading to hard to debug problems.
The plugin now errors when an unknown source is configured, or when no sources are configured.
In addition, a single string is now a valid value for sources to either enable all sources with an *, or a single source.

Fixes: #6336

To Do

• Documentation. (If you've added a new command-line flag, for example, find the appropriate page under docs/ to describe it.)
• Changelog. (Add an entry to docs/changelog.rst to the bottom of one of the lists near the top of the document.)
• Tests. (Very much encouraged but not strictly required.)

[github-actions]

Thank you for the PR! The changelog has not been updated, so here is a friendly reminder to check if you need to add an entry.

[codecov]

Codecov Report

❌ Patch coverage is 80.95238% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.19%. Comparing base (137c049) to head (142e946).
⚠️ Report is 2 commits behind head on master.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
beetsplug/fetchart.py	71.42%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6508   +/-   ##
=======================================
  Coverage   70.18%   70.19%           
=======================================
  Files         147      147           
  Lines       18680    18698   +18     
  Branches     3042     3046    +4     
=======================================
+ Hits        13111    13125   +14     
- Misses       4927     4930    +3     
- Partials      642      643    +1     

Files with missing lines	Coverage Δ
beets/util/config.py	100.00% <100.00%> (ø)
beetsplug/fetchart.py	74.24% <71.42%> (-0.17%)	⬇️

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[snejus]

Looks great, just a pair of nit-like comments

[ShimmerGlass]

@snejus all updated, added a changelog entry!

[snejus]

Thanks!

[snejus]

@ShimmerGlass Oh no, this just broke beetcamp which dynamically registers its art source:

    def loaded(self) -> None:
        """Add our own artsource to the fetchart plugin."""
        for plugin in plugins.find_plugins():
            if isinstance(plugin, fetchart.FetchArtPlugin):
                if isinstance(fetchart.ART_SOURCES, set):
                    fetchart.ART_SOURCES.add(BandcampAlbumArt)
                else:
                    fetchart.ART_SOURCES[self.data_source] = BandcampAlbumArt
                    fetchart.SOURCE_NAMES[BandcampAlbumArt] = self.data_source
                    fetchart.SOURCES_ALL.append(self.data_source)
                bandcamp_fetchart = BandcampAlbumArt(self._log, self.config)
                plugin.sources = [bandcamp_fetchart, *plugin.sources]
                break

Furthermore, I wonder why does it report bandcamp=* instead of simply bandcamp?

UserError: setting bandcamp=* is not recognized

My configuration:

fetchart:
  lastfm_key: XXX
  auto: yes
  store_source: yes
  sources:
    - filesystem
    - cover_art_url
    - bandcamp
    - lastfm
    - "*"
  maxwidth: 700

[snejus]

Ignore me: the issue is gone if I remove bandcamp from my configuration which is indeed not found since BandcampAlbumArt uses capitalised Bandcamp:

class BandcampAlbumArt(BandcampRequestsHandler, fetchart.RemoteArtSource):
    NAME = ID = "Bandcamp"

[ShimmerGlass]

no problem :)

[snejus]

@ShimmerGlass Though this question still stands:

Furthermore, I wonder why does it report bandcamp=* instead of simply bandcamp?

UserError: setting bandcamp=* is not recognized