group the downloads tree by the album's artist

The tree read the track artist off each song, so a downloaded album split into
one group per guest performer and every song without a track artist landed in
"Unknown artist". It reads the album's artist now, which is also the artist the
node's delete resolves through, so the two agree.

The badges are white glyphs with a dark outline and a progress ring with a
visible track, after a look at the rendered result; larger and clearer than the
first pass, which the art swallowed.

app/src/test/kotlin/com/subtracks/data/repo/DownloadRepositoryTest.kt

@@ -816,6 +816,41 @@ class DownloadRepositoryTest {
             assertFalse(file(1, "s2").exists())
         }
 
+    @Test
+    fun theTreeGroupsAnAlbumUnderItsAlbumArtistNotEachTrackArtist() =
+        runTest {
+            seedLibrary()
+            runBlocking {
+                db.libraryDao().upsertSongs(
+                    listOf(
+                        Song(
+                            sourceId = 1,
+                            id = "s3",
+                            albumId = "al1",
+                            artistId = "ar-guest",
+                            title = "Song 3",
+                            album = "Album",
+                            artist = "Guest",
+                            duration = 100,
+                            track = 3,
+                            disc = 1,
+                            starred = null,
+                            genre = null,
+                        ),
+                    ),
+                )
+                db.libraryDao().upsertArtists(
+                    listOf(Artist(sourceId = 1, id = "ar-guest", name = "Guest", albumCount = 0, starred = null, coverArt = null)),
+                )
+                db.downloadDao().upsert(SongDownload(1, "s1", DownloadStatus.Completed))
+                db.downloadDao().upsert(SongDownload(1, "s3", DownloadStatus.Completed))
+            }
+
+            val songs = runBlocking { repository.downloadedSongs(1).first() }
+
+            assertEquals(setOf("ar1" to "Artist"), songs.map { it.artistId to it.artistName }.toSet())
+        }
+
     private fun requestedSongIds(): List<String> = engine.requests.map { it.second.path.substringAfterLast('/') }
 
     private fun seedSongs(tracks: IntRange) {

app/src/test/kotlin/com/subtracks/ui/AppScreenshotTest.kt

@@ -32,6 +32,7 @@ import com.github.takahirom.roborazzi.captureRoboImage
 import com.subtracks.data.model.Album
 import com.subtracks.data.model.Artist
 import com.subtracks.data.model.CoverArtRef
+import com.subtracks.data.model.ListDownloadStatus
 import com.subtracks.data.model.Playlist
 import com.subtracks.data.model.PlaylistSongItem
 import com.subtracks.data.model.Song
@@ -125,6 +126,37 @@ class AppScreenshotTest {
         composeRule.onRoot().captureRoboImage("src/test/screenshots/library_scrolled_under_header.png")
     }
 
+    @Test
+    fun libraryAlbumsWithDownloads() {
+        val ids = Fixtures.albums.take(3).map { it.id }
+        composeRule.setContent {
+            SubtracksTheme {
+                LibraryScreen(
+                    selectedTab = LibraryTab.Albums,
+                    onTabSelected = {},
+                    albums = remember { flowOf(PagingData.from(Fixtures.albums)) },
+                    artists = remember { flowOf(PagingData.empty<Artist>()) },
+                    playlists = remember { flowOf(PagingData.empty<Playlist>()) },
+                    coverArt = { id, _ -> id?.let { CoverArtRef(it, "test:$it") } },
+                    onAlbumClick = {},
+                    onArtistClick = {},
+                    onPlaylistClick = {},
+                    onSync = {},
+                    onOpenSettings = {},
+                    artwork = artworkColorsFromSeed(Color.rgb(120, 80, 200)),
+                    albumDownloads =
+                        mapOf(
+                            ids[0] to ListDownloadStatus(total = 10, downloaded = 10),
+                            ids[1] to ListDownloadStatus(total = 10, downloaded = 4, downloading = 1),
+                            ids[2] to ListDownloadStatus(total = 10, downloaded = 4),
+                        ),
+                )
+            }
+        }
+        awaitTag(ALBUM_COVER_TAG)
+        composeRule.onRoot().captureRoboImage("src/test/screenshots/library_albums_downloads.png")
+    }
+
     @Test
     fun libraryArtists() {
         setLibraryContent(LibraryTab.Artists)