fix: recover Session file list from the tab layout XML (#694)

src/LogExpert.Core/Classes/Persister/SessionFileResolver.cs

@@ -1,5 +1,8 @@
 using System.Collections.ObjectModel;
+using System.Xml;
+using System.Xml.Linq;
 
+using LogExpert.Core.Enums;
 using LogExpert.Core.Interfaces;
 
 namespace LogExpert.Core.Classes.Persister;
@@ -31,4 +34,39 @@ public static class SessionFileResolver
 
         return resolved.AsReadOnly();
     }
+
+    /// <summary>
+    /// Recovers the log file paths from a Session's tab layout XML. The DockPanel layout names
+    /// every log window in a <c>PersistString="LogWindow#&lt;path&gt;"</c> attribute, so a Session
+    /// whose FileNames list is missing or empty can still be restored from its layout.
+    /// </summary>
+    /// <param name="tabLayoutXml">The DockPanel layout XML stored in the Session, may be null or malformed</param>
+    /// <returns>The log file paths in layout order; empty if the XML is null, malformed, or names no log windows</returns>
+    public static ReadOnlyCollection<string> RecoverFileNamesFromLayout (string tabLayoutXml)
+    {
+        if (string.IsNullOrWhiteSpace(tabLayoutXml))
+        {
+            return ReadOnlyCollection<string>.Empty;
+        }
+
+        var prefix = WindowTypes.LogWindow + "#";
+
+        try
+        {
+            var fileNames = XDocument.Parse(tabLayoutXml)
+                .Descendants("Content")
+                .Select(content => (string)content.Attribute("PersistString"))
+                .Where(persistString => persistString != null &&
+                                        persistString.StartsWith(prefix, StringComparison.OrdinalIgnoreCase) &&
+                                        persistString.Length > prefix.Length)
+                .Select(persistString => persistString[prefix.Length..])
+                .ToList();
+
+            return fileNames.AsReadOnly();
+        }
+        catch (XmlException)
+        {
+            return ReadOnlyCollection<string>.Empty;
+        }
+    }
 }

src/LogExpert.Core/Classes/Persister/SessionPersister.cs

@@ -35,6 +35,21 @@ public static SessionLoadResult LoadSessionData (string sessionFileName, IPlugin
 
             // Set Session file path for alternative file search
             sessionData.SessionFilePath = sessionFileName;
+            sessionData.FileNames ??= [];
+
+            // v1.42.0 wrote Sessions with an empty FileNames list (issue #694): the save path
+            // enumerated DockPanelSuite's DisplayingContents with foreach, which yields nothing.
+            // The tab layout XML in those files still names every log window, so recover from there.
+            if (sessionData.FileNames.Count == 0)
+            {
+                var recovered = SessionFileResolver.RecoverFileNamesFromLayout(sessionData.TabLayoutXml);
+
+                if (recovered.Count > 0)
+                {
+                    _logger.Warn($"Session {sessionFileName} has an empty file list; recovered {recovered.Count} file(s) from the tab layout");
+                    sessionData.FileNames = [.. recovered];
+                }
+            }
 
             // Resolve Session File (.lxp) entries to actual .log files
             var resolvedFiles = SessionFileResolver.ResolveSessionFiles(sessionData, pluginRegistry);

src/LogExpert.Persister.Tests/SessionFileResolverTests.cs

@@ -0,0 +1,197 @@
+using System.Globalization;
+using System.Text;
+
+using LogExpert.Core.Classes.Persister;
+
+using Newtonsoft.Json;
+
+namespace LogExpert.Persister.Tests;
+
+/// <summary>
+/// Tests for recovering a Session's file list from its tab layout XML (issue #694).
+/// v1.42.0 saved Sessions with an empty FileNames list; the DockPanel layout XML still
+/// names every log window, so loading falls back to it.
+/// </summary>
+[TestFixture]
+public class SessionFileResolverTests
+{
+    private string _testDirectory;
+
+    [SetUp]
+    public void Setup ()
+    {
+        _testDirectory = Path.Join(Path.GetTempPath(), "LogExpertTests", "SessionResolver", Guid.NewGuid().ToString());
+        _ = Directory.CreateDirectory(_testDirectory);
+
+        _ = PluginRegistry.PluginRegistry.Create(_testDirectory, 1000);
+    }
+
+    [TearDown]
+    [System.Diagnostics.CodeAnalysis.SuppressMessage("Design", "CA1031:Do not catch general exception types", Justification = "Unit Test")]
+    public void TearDown ()
+    {
+        try
+        {
+            if (Directory.Exists(_testDirectory))
+            {
+                Directory.Delete(_testDirectory, true);
+            }
+        }
+        catch (Exception)
+        {
+            // Ignore cleanup failures
+        }
+    }
+
+    private static string BuildLayoutXml (params string[] persistStrings)
+    {
+        StringBuilder contents = new();
+        for (var i = 0; i < persistStrings.Length; i++)
+        {
+            _ = contents.Append(CultureInfo.InvariantCulture, $"    <Content ID=\"{i}\" PersistString=\"{persistStrings[i]}\" AutoHidePortion=\"0.25\" IsHidden=\"False\" IsFloat=\"False\" />\r\n");
+        }
+
+        StringBuilder paneRefs = new();
+        for (var i = 0; i < persistStrings.Length; i++)
+        {
+            _ = paneRefs.Append(CultureInfo.InvariantCulture, $"        <Content ID=\"{i}\" RefID=\"{i}\" />\r\n");
+        }
+
+        // Shape of a real v1.42.0 layout: contents with PersistString, plus pane entries that
+        // reference them through RefID only (those must not be picked up by the recovery).
+        return "<!--DockPanel configuration file. Author: Weifen Luo, all rights reserved.-->\r\n" +
+               "<DockPanel FormatVersion=\"1.0\" DockLeftPortion=\"0.25\" DockRightPortion=\"0.25\" DockTopPortion=\"0.25\" DockBottomPortion=\"0.25\" ActiveDocumentPane=\"0\" ActivePane=\"0\">\r\n" +
+               $"  <Contents Count=\"{persistStrings.Length}\">\r\n" +
+               contents +
+               "  </Contents>\r\n" +
+               "  <Panes Count=\"1\">\r\n" +
+               "    <Pane ID=\"0\" DockState=\"Document\" ActiveContent=\"0\">\r\n" +
+               $"      <Contents Count=\"{persistStrings.Length}\">\r\n" +
+               paneRefs +
+               "      </Contents>\r\n" +
+               "    </Pane>\r\n" +
+               "  </Panes>\r\n" +
+               "  <FloatWindows Count=\"0\" />\r\n" +
+               "</DockPanel>";
+    }
+
+    private string WriteSessionFile (string fileNamesJson, string tabLayoutXml)
+    {
+        var sessionFile = Path.Join(_testDirectory, "session.lxj");
+        var layoutJson = JsonConvert.ToString(tabLayoutXml ?? string.Empty);
+        var json = $"{{\r\n  \"FileNames\": {fileNamesJson},\r\n  \"TabLayoutXml\": {layoutJson},\r\n  \"SessionFilePath\": null\r\n}}";
+        File.WriteAllText(sessionFile, json, Encoding.UTF8);
+        return sessionFile;
+    }
+
+    #region RecoverFileNamesFromLayout
+
+    [Test]
+    public void RecoverFileNamesFromLayout_LayoutWithLogWindows_ReturnsPathsInLayoutOrder ()
+    {
+        var layout = BuildLayoutXml(@"LogWindow#C:\temp\test1.log", @"LogWindow#C:\temp\test2.log");
+
+        var result = SessionFileResolver.RecoverFileNamesFromLayout(layout);
+
+        Assert.That(result, Is.EqualTo(new[] { @"C:\temp\test1.log", @"C:\temp\test2.log" }));
+    }
+
+    [TestCase(null)]
+    [TestCase("")]
+    [TestCase("   ")]
+    public void RecoverFileNamesFromLayout_NullOrWhitespace_ReturnsEmpty (string? layout)
+    {
+        var result = SessionFileResolver.RecoverFileNamesFromLayout(layout);
+
+        Assert.That(result, Is.Empty);
+    }
+
+    [Test]
+    public void RecoverFileNamesFromLayout_MalformedXml_ReturnsEmpty ()
+    {
+        var result = SessionFileResolver.RecoverFileNamesFromLayout("<DockPanel><Contents></DockPanel>");
+
+        Assert.That(result, Is.Empty);
+    }
+
+    [Test]
+    public void RecoverFileNamesFromLayout_NoLogWindowContents_ReturnsEmpty ()
+    {
+        var layout = BuildLayoutXml("BookmarkWindow");
+
+        var result = SessionFileResolver.RecoverFileNamesFromLayout(layout);
+
+        Assert.That(result, Is.Empty);
+    }
+
+    [Test]
+    public void RecoverFileNamesFromLayout_PersistStringWithoutPath_IsSkipped ()
+    {
+        var layout = BuildLayoutXml("LogWindow#", @"LogWindow#C:\temp\test1.log");
+
+        var result = SessionFileResolver.RecoverFileNamesFromLayout(layout);
+
+        Assert.That(result, Is.EqualTo(new[] { @"C:\temp\test1.log" }));
+    }
+
+    #endregion
+
+    #region SessionPersister.LoadSessionData recovery (issue #694)
+
+    [Test]
+    public void LoadSessionData_EmptyFileNamesWithLayout_RecoversFilesFromLayout ()
+    {
+        // Arrange - a Session as written by v1.42.0: empty FileNames, intact layout XML
+        var log1 = Path.Join(_testDirectory, "test1.log");
+        var log2 = Path.Join(_testDirectory, "test2.log");
+        File.WriteAllText(log1, "line1\n");
+        File.WriteAllText(log2, "line1\n");
+        var sessionFile = WriteSessionFile("[]", BuildLayoutXml($"LogWindow#{log1}", $"LogWindow#{log2}"));
+
+        // Act
+        var result = SessionPersister.LoadSessionData(sessionFile, PluginRegistry.PluginRegistry.Instance);
+
+        // Assert
+        Assert.That(result.SessionData.FileNames, Is.EqualTo(new[] { log1, log2 }));
+        Assert.That(result.ValidationResult.MissingFiles, Is.Empty);
+        Assert.That(result.RequiresUserIntervention, Is.False);
+    }
+
+    [Test]
+    public void LoadSessionData_NullFileNamesWithLayout_RecoversFilesFromLayout ()
+    {
+        var log1 = Path.Join(_testDirectory, "test1.log");
+        File.WriteAllText(log1, "line1\n");
+        var sessionFile = WriteSessionFile("null", BuildLayoutXml($"LogWindow#{log1}"));
+
+        var result = SessionPersister.LoadSessionData(sessionFile, PluginRegistry.PluginRegistry.Instance);
+
+        Assert.That(result.SessionData.FileNames, Is.EqualTo(new[] { log1 }));
+    }
+
+    [Test]
+    public void LoadSessionData_EmptyFileNamesWithoutLayout_StaysEmpty ()
+    {
+        var sessionFile = WriteSessionFile("[]", string.Empty);
+
+        var result = SessionPersister.LoadSessionData(sessionFile, PluginRegistry.PluginRegistry.Instance);
+
+        Assert.That(result.SessionData.FileNames, Is.Empty);
+    }
+
+    [Test]
+    public void LoadSessionData_FileNamesPresent_LayoutDoesNotOverrideThem ()
+    {
+        var log1 = Path.Join(_testDirectory, "listed.log");
+        var log2 = Path.Join(_testDirectory, "layout-only.log");
+        File.WriteAllText(log1, "line1\n");
+        File.WriteAllText(log2, "line1\n");
+        var sessionFile = WriteSessionFile(JsonConvert.SerializeObject(new[] { log1 }), BuildLayoutXml($"LogWindow#{log2}"));
+
+        var result = SessionPersister.LoadSessionData(sessionFile, PluginRegistry.PluginRegistry.Instance);
+
+        Assert.That(result.SessionData.FileNames, Is.EqualTo(new[] { log1 }));
+    }
+
+    #endregion
+}