Dispose the source info the processing creates itself

AudioQualityEnhancer.Tests/AudioInfoTests.cs

@@ -0,0 +1,54 @@
+using System.Globalization;
+using AudioQualityEnhancer.Models;
+using AudioQualityEnhancer.Services;
+
+namespace AudioQualityEnhancer.Tests;
+
+public sealed class AudioInfoTests
+{
+    /// <summary>
+    /// AudioInfo subscribes to the localization service in its constructor so its display
+    /// strings follow a language change. That service lives for the whole session, so an
+    /// instance that is never disposed stays reachable through it for just as long. This
+    /// pins the contract that makes disposal matter.
+    /// </summary>
+    [Fact]
+    public void Dispose_StopsListeningForLanguageChanges()
+    {
+        var info = new AudioInfo { Codec = "mp3" };
+        var notifications = 0;
+        var original = LocalizationService.Instance.Culture;
+
+        try
+        {
+            // Start from a known culture. Another test class may have left the process on
+            // English, and assigning the same culture again raises no change at all.
+            LocalizationService.Instance.Culture = CultureInfo.GetCultureInfo("de");
+            info.PropertyChanged += (_, _) => notifications++;
+
+            LocalizationService.Instance.Culture = CultureInfo.GetCultureInfo("en");
+            var whileSubscribed = notifications;
+            Assert.True(whileSubscribed > 0, "A language change has to reach a live instance.");
+
+            info.Dispose();
+            LocalizationService.Instance.Culture = CultureInfo.GetCultureInfo("de");
+
+            Assert.Equal(whileSubscribed, notifications);
+        }
+        finally
+        {
+            LocalizationService.Instance.Culture = original;
+            info.Dispose();
+        }
+    }
+
+    [Fact]
+    public void WithSelectedAudioStream_ReturnsTheSameInstanceWithoutStreams()
+    {
+        using var info = new AudioInfo { Codec = "mp3" };
+
+        // Returning this is what keeps BatchProcessingItem.SelectAudioStream from handing
+        // an instance to SetAudioInfo that would then be disposed and stored at once.
+        Assert.Same(info, info.WithSelectedAudioStream(null));
+    }
+}

Services/AudioProcessingService.cs

@@ -85,18 +85,32 @@ public async Task<Result<ProcessResult>> ProcessAsync(
         _fileNameService.CleanupTemporaryOutputFiles(options.OutputDirectory, TimeSpan.FromDays(2));
 
         var sourceInfo = options.SourceInfo;
-        if (sourceInfo is null)
+        if (sourceInfo is not null)
         {
-            Report(progress, 8, LocalizationService.Instance["Phase_AnalyzingSource"]);
-            var analysis = await _ffprobeService.AnalyzeAsync(options.InputPath, _logService.Info, cancellationToken);
-            if (analysis.IsFailure || analysis.Value is null)
-            {
-                return Result<ProcessResult>.Failure(analysis.ErrorMessage ?? LocalizationService.Instance["Error_SourceAnalysisFailed"], analysis.Exception);
-            }
+            // Supplied by the caller, so it belongs to the queue item and is disposed with it.
+            return await RenderAsync(options, sourceInfo, progress, cancellationToken);
+        }
 
-            sourceInfo = analysis.Value;
+        Report(progress, 8, LocalizationService.Instance["Phase_AnalyzingSource"]);
+        var analysis = await _ffprobeService.AnalyzeAsync(options.InputPath, _logService.Info, cancellationToken);
+        if (analysis.IsFailure || analysis.Value is null)
+        {
+            return Result<ProcessResult>.Failure(analysis.ErrorMessage ?? LocalizationService.Instance["Error_SourceAnalysisFailed"], analysis.Exception);
         }
 
+        // Created here, so disposed here. AudioInfo subscribes to the localization
+        // service in its constructor, and that service outlives the run, so an
+        // undisposed instance would stay reachable for the rest of the session.
+        using var ownedSourceInfo = analysis.Value;
+        return await RenderAsync(options, ownedSourceInfo, progress, cancellationToken);
+    }
+
+    private async Task<Result<ProcessResult>> RenderAsync(
+        ProcessingOptions options,
+        AudioInfo sourceInfo,
+        IProgress<ProcessingProgress>? progress,
+        CancellationToken cancellationToken)
+    {
         var diskSpaceCheck = EnsureSufficientDiskSpace(options.OutputDirectory, EstimateOutputSizeBytes(options, sourceInfo));
         if (diskSpaceCheck.IsFailure)
         {