From 87cd3f1037d02170990db9eb56f328e7cdfb7548 Mon Sep 17 00:00:00 2001
From: Deluan <deluan@navidrome.org>
Date: Sun, 24 May 2026 21:37:01 -0300
Subject: [PATCH] fix(scanner): treat explicit '[Unknown Artist]' ALBUMARTIST
 as missing

The old parseArtists function (removed in this branch) substituted
consts.UnknownArtist when albumartist tags were empty, so the
downstream compilation/fallback check matched both cases. The
inlined replacement only checked len(albumNames)==0, narrowing the
condition: files explicitly tagged ALBUMARTIST='[Unknown Artist]'
(emitted by some rippers, and matching what Navidrome itself stores
for untagged files) stopped routing to Various Artists for
compilations.

Restore the original semantics by treating len==1 with the literal
UnknownArtist string as equivalent to no tag.
---
 model/metadata/map_participants.go      | 10 +++++++++-
 model/metadata/map_participants_test.go | 20 ++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/model/metadata/map_participants.go b/model/metadata/map_participants.go
index b5c6e0c38..4c9c0de01 100644
--- a/model/metadata/map_participants.go
+++ b/model/metadata/map_participants.go
@@ -53,8 +53,16 @@ func (md Metadata) mapParticipants() model.Participants {
 	albumMbids := md.Strings(model.TagMusicBrainzAlbumArtistID)
 	albumCredits := md.getArtistValues(model.TagAlbumArtistCredit, model.TagAlbumArtistsCredit)
 
+	// Treat both "no albumartist tag" and "albumartist tag literally set to
+	// the UnknownArtist placeholder" as missing — some rippers emit the
+	// literal '[Unknown Artist]' string, and the original parseArtists path
+	// (replaced in this branch) substituted UnknownArtist on its own so the
+	// downstream check matched either case.
+	albumArtistMissing := len(albumNames) == 0 ||
+		(len(albumNames) == 1 && albumNames[0] == consts.UnknownArtist)
+
 	var albumArtistParticipants []model.Participant
-	if len(albumNames) == 0 {
+	if albumArtistMissing {
 		if md.Bool(model.TagCompilation) {
 			albumArtistParticipants = md.buildParticipants(
 				[]string{consts.VariousArtists}, nil,
diff --git a/model/metadata/map_participants_test.go b/model/metadata/map_participants_test.go
index 7ef6183ee..3467bb99f 100644
--- a/model/metadata/map_participants_test.go
+++ b/model/metadata/map_participants_test.go
@@ -460,6 +460,26 @@ var _ = Describe("Participants", func() {
 				})
 			})
 
+			When("the COMPILATION tag is true and ALBUMARTIST is the UnknownArtist placeholder", func() {
+				BeforeEach(func() {
+					// Some rippers emit the literal '[Unknown Artist]' string
+					// when no album artist is set. The fallback must still
+					// route to Various Artists for compilations.
+					mf = toMediaFile(model.RawTags{
+						"COMPILATION": {"1"},
+						"ALBUMARTIST": {consts.UnknownArtist},
+					})
+				})
+
+				It("should substitute Various Artists as the album artist", func() {
+					participants := mf.Participants
+					Expect(participants).To(HaveKeyWithValue(model.RoleAlbumArtist, HaveLen(1)))
+					albumArtist := participants[model.RoleAlbumArtist][0]
+					Expect(albumArtist.Name).To(Equal("Various Artists"))
+					Expect(albumArtist.MbzArtistID).To(Equal(consts.VariousArtistsMbzId))
+				})
+			})
+
 			When("the COMPILATION tag is true and there are ALBUMARTIST tags", func() {
 				BeforeEach(func() {
 					mf = toMediaFile(model.RawTags{