Fix KeyError during artist download pagination

[LiuqingDu]

Pull Request: Fix KeyError during artist download pagination

Problem

When using artist download options like --artist-auto-select all-albums on artists with a large number of releases (triggering the API pagination logic), the downloader would crash with a KeyError: 'id'.

This was caused by the code incorrectly extending the data list with the entire response dictionary (which contains data and next keys) instead of extracting and extending with the nested data list. When the subsequent loop tried to read album_metadata["id"] from that dictionary object, it failed.

Solution

Replaced the erroneous list comprehension with an explicit async for loop that correctly extends the results with extended_data["data"].

# Before (Buggy)
artist_metadata[relation_key][type_key]["data"].extend(
    [
        extended_data
        async for extended_data in self.interface.apple_music_api.extend_api_data(...)
    ]
)

# After (Fixed)
async for extended_data in self.interface.apple_music_api.extend_api_data(...):
    artist_metadata[relation_key][type_key]["data"].extend(extended_data["data"])

This change ensures only album-like objects are in the list and makes the logic consistent with similar pagination handling found elsewhere in the codebase (e.g., in get_collection_download_items).

Testing

Verified by running gamdl on an artist with a large number of singles/albums (e.g., Megan Nicole).

• Before fix: Process crashed with KeyError: 'id' once pagination was triggered.
• After fix: Successfully fetched all pages and queued all tracks for download.

[LiuqingDu]

I encountered this issue. this fix is made by AI.

test url: https://music.apple.com/us/artist/megan-nicole/380531205