Gui Settings Null list Entries (#430)

src/SharpEmu.GUI/GuiSettings.cs

@@ -71,7 +71,7 @@ public sealed class GuiSettings
             if (File.Exists(SettingsPath))
             {
                 var json = File.ReadAllText(SettingsPath);
-                return JsonSerializer.Deserialize<GuiSettings>(json, SerializerOptions) ?? new GuiSettings();
+                return NormalizeFromJson(json);
             }
         }
         catch (Exception)
@@ -82,6 +82,35 @@ public sealed class GuiSettings
         return new GuiSettings();
     }
 
+    /// <summary>
+    /// Deserializes settings and normalizes null references and null or empty list
+    /// entries introduced by JSON. Empty scalar strings remain unchanged.
+    /// </summary>
+    internal static GuiSettings NormalizeFromJson(string json)
+    {
+        var settings = JsonSerializer.Deserialize<GuiSettings>(json, SerializerOptions) ?? new GuiSettings();
+
+        settings.GameFolders = FilterNullOrEmpty(settings.GameFolders);
+        settings.ExcludedGames = FilterNullOrEmpty(settings.ExcludedGames);
+        settings.EnvironmentToggles = FilterNullOrEmpty(settings.EnvironmentToggles);
+        settings.LogLevel ??= "Info";
+        settings.Language ??= "en";
+        settings.DiscordClientId ??= "1525606762248540221";
+
+        return settings;
+    }
+
+    // JSON can populate non-nullable lists with null references and entries.
+    private static List<string> FilterNullOrEmpty(List<string>? source)
+    {
+        if (source is null)
+        {
+            return [];
+        }
+
+        return source.Where(entry => !string.IsNullOrEmpty(entry)).ToList();
+    }
+
     public void Save()
     {
         try

src/SharpEmu.GUI/SharpEmu.GUI.csproj

@@ -24,6 +24,10 @@ SPDX-License-Identifier: GPL-2.0-or-later
     <ProjectReference Include="..\SharpEmu.Logging\SharpEmu.Logging.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <InternalsVisibleTo Include="SharpEmu.Libs.Tests" />
+  </ItemGroup>
+
   <ItemGroup>
     <PackageReference Include="Avalonia" />
     <PackageReference Include="Avalonia.Desktop" />

tests/SharpEmu.Libs.Tests/GUI/GuiSettingsTests.cs

@@ -0,0 +1,100 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using SharpEmu.GUI;
+using Xunit;
+
+namespace SharpEmu.Libs.Tests.GUI;
+
+public sealed class GuiSettingsTests
+{
+    [Fact]
+    public void NormalizeFromJson_AllPropertiesNull_FallsBackToDefaults()
+    {
+        const string json = """
+            {
+              "LogLevel": null,
+              "GameFolders": null,
+              "ExcludedGames": null,
+              "EnvironmentToggles": null,
+              "Language": null,
+              "DiscordClientId": null
+            }
+            """;
+
+        var settings = GuiSettings.NormalizeFromJson(json);
+
+        Assert.Equal("Info", settings.LogLevel);
+        Assert.Equal("en", settings.Language);
+        Assert.Equal("1525606762248540221", settings.DiscordClientId);
+        Assert.Empty(settings.GameFolders);
+        Assert.Empty(settings.ExcludedGames);
+        Assert.Empty(settings.EnvironmentToggles);
+    }
+
+    [Fact]
+    public void NormalizeFromJson_ValidValues_ArePreserved()
+    {
+        const string json = """
+            {
+              "LogLevel": "Debug",
+              "GameFolders": ["C:\\Games"],
+              "ExcludedGames": ["C:\\Games\\skip.bin"],
+              "EnvironmentToggles": ["SHARPEMU_TRACE"],
+              "Language": "pt-BR",
+              "DiscordClientId": "999"
+            }
+            """;
+
+        var settings = GuiSettings.NormalizeFromJson(json);
+
+        Assert.Equal("Debug", settings.LogLevel);
+        Assert.Equal("pt-BR", settings.Language);
+        Assert.Equal("999", settings.DiscordClientId);
+        Assert.Equal(["C:\\Games"], settings.GameFolders);
+        Assert.Equal(["C:\\Games\\skip.bin"], settings.ExcludedGames);
+        Assert.Equal(["SHARPEMU_TRACE"], settings.EnvironmentToggles);
+    }
+
+    // An empty Discord client ID intentionally disables Rich Presence.
+    [Fact]
+    public void NormalizeFromJson_EmptyDiscordClientId_IsPreservedNotNormalized()
+    {
+        const string json = """{ "DiscordClientId": "" }""";
+
+        var settings = GuiSettings.NormalizeFromJson(json);
+
+        Assert.Equal(string.Empty, settings.DiscordClientId);
+    }
+
+    [Fact]
+    public void NormalizeFromJson_NullOrEmptyListEntries_AreFilteredOut()
+    {
+        const string json = """
+            {
+              "GameFolders": ["C:\\Games", null, ""],
+              "ExcludedGames": [null],
+              "EnvironmentToggles": [null, "SHARPEMU_TRACE", ""]
+            }
+            """;
+
+        var settings = GuiSettings.NormalizeFromJson(json);
+
+        Assert.Equal(["C:\\Games"], settings.GameFolders);
+        Assert.Empty(settings.ExcludedGames);
+        Assert.Equal(["SHARPEMU_TRACE"], settings.EnvironmentToggles);
+    }
+
+    [Fact]
+    public void NormalizeFromJson_EmptyObject_UsesConstructorDefaults()
+    {
+        var settings = GuiSettings.NormalizeFromJson("{}");
+
+        Assert.Equal("Info", settings.LogLevel);
+        Assert.Equal("en", settings.Language);
+        Assert.Equal("1525606762248540221", settings.DiscordClientId);
+        Assert.Empty(settings.GameFolders);
+        Assert.Empty(settings.ExcludedGames);
+        Assert.Empty(settings.EnvironmentToggles);
+    }
+}

tests/SharpEmu.Libs.Tests/SharpEmu.Libs.Tests.csproj

@@ -14,6 +14,7 @@ SPDX-License-Identifier: GPL-2.0-or-later
     <ProjectReference Include="..\..\src\SharpEmu.Core\SharpEmu.Core.csproj" />
     <ProjectReference Include="..\..\src\SharpEmu.Libs\SharpEmu.Libs.csproj" />
     <ProjectReference Include="..\..\src\SharpEmu.HLE\SharpEmu.HLE.csproj" />
+    <ProjectReference Include="..\..\src\SharpEmu.GUI\SharpEmu.GUI.csproj" />
   </ItemGroup>
 
   <ItemGroup>