Missing attributes when getting related resources: get_artist, get_tracks, get_albums, get_episodes...

[browniebroke]

The Deezer API returns fewer fields when retrieving a resource as a relation than when the resource is returned directly. Exampels include:

• A single track vs list of album tracks
• A single artist vs the artist field of an album
• A single episode vs listing episodes of a podcast
• A podcast vs the nested podcast field on an episode

If we look at the 2nd example, from the library usage perspective, it can be confusing. The API are supposed to return the same resources, but in some cases they return a "shallow" version, with fewer fields and if the user tries to access the missing ones, they'll get an AttributeError.

In the case of the album's artist, there are 2 ways of getting it:

1. Album.artist field
2. Album.get_artist() method

The first one doesn't make any API call to Deezer, however it returns an incomplete object with only the following fields: id, name, picture, picture_small, picture_medium, picture_big, picture_xl. The artist returned is missing a few fields which are type annotated as always present:

deezer-python/deezer/resources.py

Lines 180 to 183 in 93e473a

	nb_album: int
	nb_fan: int
	radio: bool
	tracklist: str

The second way, using the method, returns a full object, at the cost of an extra API call.

It's a problem for a couple of reasons:

• It's not clear from the library API which way should I use to get the album artist
• If I'm using the 1st way, I might later get an attribute error due to the wrong type hints