fix(musicbrainz): search a compilation's release as Various Artists

src/components/bulk-musicbrainz-modal/helpers.test.ts

@@ -0,0 +1,56 @@
+import { describe, expect, it } from 'vitest'
+import type { BulkMusicBrainzSong } from '@/features/musicbrainz/bulk-lookup'
+import { initialReleaseSearch, releaseArtist, VARIOUS_ARTISTS } from './helpers'
+
+function song(artist: string | null, albumArtist: string | null = null, album = 'Album'): BulkMusicBrainzSong {
+  return { artist, albumArtist, album } as BulkMusicBrainzSong
+}
+
+describe('releaseArtist', () => {
+  it('uses the album artist when the files carry one', () => {
+    expect(releaseArtist([song('Artist A', 'Various Artists'), song('Artist B', 'Various Artists')])).toBe(
+      'Various Artists'
+    )
+    expect(releaseArtist([song('Queen'), song('Queen & David Bowie', 'Queen')])).toBe('Queen')
+  })
+
+  it('uses the track artist for a regular album', () => {
+    expect(releaseArtist([song('Daft Punk'), song('Daft Punk'), song('Daft Punk')])).toBe('Daft Punk')
+  })
+
+  it('searches for Various Artists when every track has a different artist', () => {
+    expect(releaseArtist([song('Madonna'), song('Prince'), song('Blondie'), song('Toto')])).toBe(VARIOUS_ARTISTS)
+  })
+
+  it('searches for Various Artists when no artist has more than half of the tracks', () => {
+    expect(releaseArtist([song('Madonna'), song('Madonna'), song('Prince'), song('Blondie')])).toBe(VARIOUS_ARTISTS)
+  })
+
+  it('does not treat guest appearances as different artists', () => {
+    expect(
+      releaseArtist([
+        song('Kendrick Lamar'),
+        song('Kendrick Lamar feat. SZA'),
+        song('Kendrick Lamar & Rihanna'),
+        song('Kendrick Lamar ft. Drake'),
+        song('Kendrick Lamar')
+      ])
+    ).toBe('Kendrick Lamar')
+  })
+
+  it('keeps a single song and empty selections as they are', () => {
+    expect(releaseArtist([song('Prince')])).toBe('Prince')
+    expect(releaseArtist([song(null), song('  ')])).toBe('')
+  })
+})
+
+describe('initialReleaseSearch', () => {
+  it('fills album and artist for a compilation', () => {
+    expect(initialReleaseSearch([song('Madonna', null, 'Bravo Hits 1'), song('Prince', null, 'Bravo Hits 1')])).toEqual(
+      {
+        album: 'Bravo Hits 1',
+        artist: VARIOUS_ARTISTS
+      }
+    )
+  })
+})

src/components/bulk-musicbrainz-modal/helpers.ts

@@ -16,10 +16,37 @@ export function mostCommon(values: Array<string | null | undefined>): string {
   return [...counts.entries()].sort((a, b) => b[1] - a[1])[0]?.[0] ?? ''
 }
 
+/** MusicBrainz' own name for releases by several artists (its special purpose artist). */
+export const VARIOUS_ARTISTS = 'Various Artists'
+
+/** "Kendrick Lamar feat. SZA" -> "Kendrick Lamar", so guest appearances don't look like different artists. */
+function primaryArtist(artist: string): string {
+  return artist
+    .split(/\s+(?:feat\.?|ft\.?|featuring|with|&|x|vs\.?)\s+|\s*[,;/]\s*/i)[0]
+    .trim()
+    .toLowerCase()
+}
+
+/**
+ * The artist to search the release by: the album artist when the files carry one, otherwise the track artist -
+ * unless no artist (guests aside) appears on more than half of the songs, which makes it a compilation.
+ */
+export function releaseArtist(songs: BulkMusicBrainzSong[]): string {
+  const albumArtist = mostCommon(songs.map(song => song.albumArtist))
+  if (albumArtist) return albumArtist
+
+  const artists = songs.map(song => song.artist?.trim()).filter((artist): artist is string => !!artist)
+  const primaries = artists.map(primaryArtist)
+  const top = mostCommon(primaries)
+  const topCount = primaries.filter(primary => primary === top).length
+  if (artists.length > 1 && topCount * 2 <= artists.length) return VARIOUS_ARTISTS
+  return mostCommon(artists.filter(artist => primaryArtist(artist) === top))
+}
+
 export function initialReleaseSearch(songs: BulkMusicBrainzSong[]) {
   return {
     album: mostCommon(songs.map(song => song.album)),
-    artist: mostCommon(songs.map(song => song.albumArtist || song.artist))
+    artist: releaseArtist(songs)
   }
 }