Add opt-in pref mergeContributorsByName for album-artist contributor matching

Changelog9.html

@@ -2,7 +2,7 @@ <h2><a name="v9.0.4" id="v9.0.4"></a>Version 9.0.4</h2>
 <ul>
 	<li>New Features:</li>
 	<ul>
-		<li></li>
+		<li><a href="https://github.com/LMS-Community/slimserver/issues/1578">#1578</a> - Add opt-in "Merge contributors by name" preference to prevent duplicate album-artist browse entries when MusicBrainz IDs differ across the same display name.</li>
 	</ul>
 	<br />
 

HTML/EN/settings/server/behavior.html

@@ -105,6 +105,11 @@
 			<label for="pref_useTPE2AsAlbumArtist1" class="stdlabel">[% 'SETUP_USETPE2ASALBUMARTIST_1' | getstring %]</label><br/>
 		[% END %]
 
+		[% WRAPPER settingGroup title="SETUP_MERGECONTRIBUTORSBYNAME" desc="SETUP_MERGECONTRIBUTORSBYNAME_DESC" %]
+			<input type="checkbox" name="pref_mergeContributorsByName" id="pref_mergeContributorsByName" value="1" [% IF prefs.pref_mergeContributorsByName %]checked="checked"[% END %] />
+			<label for="pref_mergeContributorsByName" class="stdlabel">[% 'SETUP_MERGECONTRIBUTORSBYNAME_LABEL' | getstring %]</label>
+		[% END %]
+
 		[% WRAPPER settingGroup title="SETUP_MYCLASSICALGENRES" desc="SETUP_MYCLASSICALGENRES_DESC" %]
 			<input type="text" class="stdedit" name="pref_myClassicalGenres" id="myClassicalGenres" value="[% prefs.pref_myClassicalGenres | html %]" size="40" placeholder="[% "GENRES" | string | html %]"><br/>
 		[% END %]

Slim/Schema/Contributor.pm

@@ -258,8 +258,19 @@ sub add {
 		my $mbid   = $brainzIDList[$i];
 		my ($id, $oldExtId, $oldMbid, $sth);
 
-		# check Musicbrainz ID first
-		if ($mbid) {
+		my $preferNameMatch = $prefs->get('mergeContributorsByName');
+
+		# Default behaviour: check Musicbrainz ID first, name fallback
+		# only against rows whose musicbrainz_id is NULL.
+		#
+		# When mergeContributorsByName is enabled: look up by name first
+		# regardless of MBID, tie-breaking by preferring rows with a
+		# non-null musicbrainz_id (richer data) then by id ascending
+		# (oldest first) for determinism. MBID lookup is the fallback.
+		# This is opt-in because some libraries legitimately rely on
+		# MBIDs to distinguish two artists who share a display name
+		# (e.g. John Williams the composer vs. the guitarist).
+		if ($mbid && !$preferNameMatch) {
 			$sth = $dbh->prepare_cached( 'SELECT id, extid, musicbrainz_id FROM contributors WHERE musicbrainz_id = ?' );
 			$sth->execute($mbid);
 			($id, $oldExtId, $oldMbid) = $sth->fetchrow_array;
@@ -273,6 +284,24 @@ sub add {
 				$sth->finish;
 			}
 		}
+		elsif ($preferNameMatch && $name) {
+			$sth = $dbh->prepare_cached(
+				'SELECT id, extid, musicbrainz_id FROM contributors WHERE name = ? '
+				. 'ORDER BY (musicbrainz_id IS NULL), id LIMIT 1'
+			);
+			$sth->execute($name);
+			($id, $oldExtId, $oldMbid) = $sth->fetchrow_array;
+			$sth->finish;
+
+			# If no name match, fall back to MBID lookup so a brand-new
+			# contributor doesn't get split off from an existing MBID-only row.
+			if ( !$id && $mbid ) {
+				$sth = $dbh->prepare_cached( 'SELECT id, extid, musicbrainz_id FROM contributors WHERE musicbrainz_id = ?' );
+				$sth->execute($mbid);
+				($id, $oldExtId, $oldMbid) = $sth->fetchrow_array;
+				$sth->finish;
+			}
+		}
 		else {
 			$sth = $dbh->prepare_cached( 'SELECT id, extid, musicbrainz_id FROM contributors WHERE name = ? LIMIT 1' );
 			$sth->execute($name);

Slim/Utils/Prefs.pm

@@ -189,6 +189,7 @@ sub init {
 		'variousArtistAutoIdentification' => 1,
 		'useUnifiedArtistsList' => 0,
 		'useTPE2AsAlbumArtist'  => 1,
+		'mergeContributorsByName' => 0,
 		'variousArtistsString'  => undef,
 		'releaseTypesToIgnore'  => [],
 		'ignoreReleaseTypes'    => 0,
@@ -403,7 +404,7 @@ sub init {
 
 	$prefs->setChange(
 		sub { Slim::Control::Request::executeRequest(undef, ['wipecache', $prefs->get('dontTriggerScanOnPrefChange') ? 'queue' : undef]) },
-		qw(splitList groupdiscs useTPE2AsAlbumArtist cleanupReleaseTypes worksScan)
+		qw(splitList groupdiscs useTPE2AsAlbumArtist mergeContributorsByName cleanupReleaseTypes worksScan)
 	);
 
 	$prefs->setChange( sub {

Slim/Web/Settings/Server/Behavior.pm

@@ -31,7 +31,7 @@ sub prefs {
 				ignoreReleaseTypes cleanupReleaseTypes groupArtistAlbumsByReleaseType
 				useTPE2AsAlbumArtist variousArtistsString ratingImplementation useUnifiedArtistsList
 				skipsentinel showComposerReleasesbyAlbum myClassicalGenres onlyAlbumYears
-				worksScan)
+				worksScan mergeContributorsByName)
 		   );
 }
 

strings.txt

@@ -20219,6 +20219,15 @@ SETUP_USETPE2ASALBUMARTIST_0
 	RU	Поле TPE2 тега MP3 содержит группу
 	SV	Behandla mp3-taggen TPE2 som band
 
+SETUP_MERGECONTRIBUTORSBYNAME
+	EN	Merge contributors by name
+
+SETUP_MERGECONTRIBUTORSBYNAME_DESC
+	EN	When two tracks share the same album artist display name but carry different MusicBrainz Album Artist IDs (e.g. a band credit on MusicBrainz that uses the solo artist's name string), LMS normally creates separate contributor rows — causing duplicate browse entries for the same apparent artist. Enable this option to match contributors by display name first, ignoring MBID differences, so those tracks are grouped under a single entry. Leave disabled if your library contains genuinely distinct artists who share a name and you rely on MusicBrainz IDs to keep them apart. Changing this setting will trigger a rescan.
+
+SETUP_MERGECONTRIBUTORSBYNAME_LABEL
+	EN	Merge album artist contributors with the same name, even when MusicBrainz IDs differ
+
 LYRICS
 	CS	Texty písní
 	DA	Tekster