fix: use und language tag with local subtitles (#2925)

CHANGELOG.md

@@ -23,6 +23,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
   - Content with multiple sidecar subtitles would incorrectly have the subtitle metadata merged (like language)
   - More rarely, content with an embedded subtitle that has stream index zero would create invalid subtitle records
   - Both cases will automatically be cleaned up during the next local library scan
+- Use `und` language tag with sidecar subtitles that have no language in the file name
 
 ## [26.5.1] - 2026-05-08
 ### Fixed

ErsatzTV.Scanner.Tests/Core/Metadata/LocalSubtitlesProviderTests.cs

@@ -98,6 +98,8 @@ public class LocalSubtitlesProviderTests
             new(@"/Movies/Avatar (2009)/Avatar (2009).en.sdh.srt"),
             new(@"/Movies/Avatar (2009)/Avatar (2009).sdh.en.srt"),
             new(@"/Movies/Avatar (2009)/Avatar (2009).de.srt"),
+            new(@"/Movies/Avatar (2009)/Avatar (2009).srt"),
+            new(@"/Movies/Avatar (2009)/Avatar (2009).forced.srt"),
 
             // non-uniform (lower-case) extensions should also work
             new(@"/Movies/Avatar (2009)/Avatar (2009).DE.SDH.FORCED.SRT")
@@ -122,14 +124,72 @@ public class LocalSubtitlesProviderTests
             @"/Movies/Avatar (2009)/Avatar (2009).mkv",
             false);
 
-        result.Count.ShouldBe(7);
+        result.Count.ShouldBe(9);
         result.Count(s => s.Language == "eng").ShouldBe(5);
         result.Count(s => s.Language == "deu").ShouldBe(2);
-        result.Count(s => s.Forced).ShouldBe(3);
+        result.Count(s => s.Language == "und").ShouldBe(2);
+        result.Count(s => s.Forced).ShouldBe(4);
         result.Count(s => s.SDH).ShouldBe(3);
-        result.Count(s => s.Codec == "subrip").ShouldBe(5);
+        result.Count(s => s.Codec == "subrip").ShouldBe(7);
         result.Count(s => s.Codec == "ass").ShouldBe(2);
 
         result.Count(s => s.Path.Contains("/Movies/Avatar (2009)")).ShouldBe(0);
     }
+
+    [Test]
+    public void Should_Not_Mark_Forced_From_Movie_title()
+    {
+        // normally this will have a full list from the database, but we just need these two for testing
+        var cultures = new List<CultureInfo>
+        {
+            CultureInfo.GetCultureInfo("en-US"),
+            CultureInfo.GetCultureInfo("de-DE")
+        };
+
+        var fakeFiles = new List<FakeFileEntry>
+        {
+            new(@"/Movies/Bloodfist.III.Forced.To.Fight.1991/Bloodfist.III.Forced.To.Fight.1991.mkv"),
+            new(@"/Movies/Bloodfist.III.Forced.To.Fight.1991/Bloodfist.III.Forced.To.Fight.1991.eng.srt"),
+            new(@"/Movies/Bloodfist.III.Forced.To.Fight.1991/Bloodfist.III.Forced.To.Fight.1991.en.forced.ass"),
+            new(@"/Movies/Bloodfist.III.Forced.To.Fight.1991/Bloodfist.III.Forced.To.Fight.1991.forced.en.ass"),
+            new(@"/Movies/Bloodfist.III.Forced.To.Fight.1991/Bloodfist.III.Forced.To.Fight.1991.en.sdh.srt"),
+            new(@"/Movies/Bloodfist.III.Forced.To.Fight.1991/Bloodfist.III.Forced.To.Fight.1991.sdh.en.srt"),
+            new(@"/Movies/Bloodfist.III.Forced.To.Fight.1991/Bloodfist.III.Forced.To.Fight.1991.de.srt"),
+            new(@"/Movies/Bloodfist.III.Forced.To.Fight.1991/Bloodfist.III.Forced.To.Fight.1991.srt"),
+            new(@"/Movies/Bloodfist.III.Forced.To.Fight.1991/Bloodfist.III.Forced.To.Fight.1991.forced.srt"),
+
+            // non-uniform (lower-case) extensions should also work
+            new(@"/Movies/Bloodfist.III.Forced.To.Fight.1991/Bloodfist.III.Forced.To.Fight.1991.DE.SDH.FORCED.SRT")
+        };
+
+        var fileSystem = new MockFileSystem(o => o.SimulatingOperatingSystem(SimulationMode.Linux));
+        IFileSystemInitializer<MockFileSystem> init = fileSystem.Initialize();
+        foreach (var file in fakeFiles)
+        {
+            init.WithFile(file.Path);
+        }
+
+        var provider = new LocalSubtitlesProvider(
+            Substitute.For<IMediaItemRepository>(),
+            Substitute.For<IMetadataRepository>(),
+            fileSystem,
+            new LocalFileSystem(fileSystem, Substitute.For<ILogger<LocalFileSystem>>()),
+            Substitute.For<ILogger<LocalSubtitlesProvider>>());
+
+        List<Subtitle> result = provider.LocateExternalSubtitles(
+            cultures,
+            @"/Movies/Bloodfist.III.Forced.To.Fight.1991/Bloodfist.III.Forced.To.Fight.1991.mkv",
+            false);
+
+        result.Count.ShouldBe(9);
+        result.Count(s => s.Language == "eng").ShouldBe(5);
+        result.Count(s => s.Language == "deu").ShouldBe(2);
+        result.Count(s => s.Language == "und").ShouldBe(2);
+        result.Count(s => s.Forced).ShouldBe(4);
+        result.Count(s => s.SDH).ShouldBe(3);
+        result.Count(s => s.Codec == "subrip").ShouldBe(7);
+        result.Count(s => s.Codec == "ass").ShouldBe(2);
+
+        result.Count(s => s.Path.Contains("/Movies/Bloodfist.III.Forced.To.Fight.1991")).ShouldBe(0);
+    }
 }

ErsatzTV.Scanner/Core/Metadata/LocalSubtitlesProvider.cs

@@ -138,32 +138,35 @@ public class LocalSubtitlesProvider : ILocalSubtitlesProvider
                 continue;
             }
 
-            string language = _fileSystem.Path.GetFileName(lowerFile);
+            string fileNameWithoutExtension = _fileSystem.Path.GetFileNameWithoutExtension(lowerFile);
+            string suffix = fileNameWithoutExtension[withoutExtension.Length..].ToLowerInvariant();
             var forced = false;
             var sdh = false;
 
-            if (lowerFile.Contains(".forced."))
+            if (suffix.Contains(".forced"))
             {
                 forced = true;
-                language = language.Replace(".forced", string.Empty);
+                suffix = suffix.Replace(".forced", string.Empty);
             }
 
-            if (lowerFile.Contains(".sdh"))
+            if (suffix.Contains(".sdh"))
             {
                 sdh = true;
-                language = language.Replace(".sdh", string.Empty);
+                suffix = suffix.Replace(".sdh", string.Empty);
             }
 
 
-            if (lowerFile.Contains(".cc."))
+            if (suffix.Contains(".cc"))
             {
                 sdh = true;
-                language = language.Replace(".cc", string.Empty);
+                suffix = suffix.Replace(".cc", string.Empty);
             }
 
-            language = language
+            // use und when no language is present
-                .Replace($"{withoutExtension.ToLowerInvariant()}.", string.Empty)[..3]
+            string language = suffix.Replace(".", string.Empty);
-                .Replace(".", string.Empty);
+            language = string.IsNullOrWhiteSpace(language)
+                ? "und"
+                : language[..Math.Min(3, language.Length)];
 
             Option<CultureInfo> maybeCulture = languageCodes.Find(ci =>
                 ci.TwoLetterISOLanguageName == language || ci.ThreeLetterISOLanguageName == language);