PerGameSettings Null toggles (#453)

src/SharpEmu.GUI/PerGameSettings.cs

@@ -49,7 +49,7 @@ public sealed class PerGameSettings
             var path = PathFor(titleId);
             if (File.Exists(path))
             {
-                return JsonSerializer.Deserialize<PerGameSettings>(File.ReadAllText(path), SerializerOptions);
+                return NormalizeFromJson(File.ReadAllText(path));
             }
         }
         catch (Exception)
@@ -59,6 +59,18 @@ public sealed class PerGameSettings
         return null;
     }
 
+    // A null list inherits global settings; only entries in a present list are sanitized.
+    internal static PerGameSettings? NormalizeFromJson(string json)
+    {
+        var settings = JsonSerializer.Deserialize<PerGameSettings>(json, SerializerOptions);
+        if (settings?.EnvironmentToggles is { } toggles)
+        {
+            settings.EnvironmentToggles = toggles.Where(entry => !string.IsNullOrEmpty(entry)).ToList();
+        }
+
+        return settings;
+    }
+
     public void Save(string titleId)
     {
         if (string.IsNullOrWhiteSpace(titleId))

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

@@ -0,0 +1,60 @@
+// 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 PerGameSettingsTests
+{
+    // Invalid entries must not reach Environment.SetEnvironmentVariable.
+    [Fact]
+    public void NormalizeFromJson_NullOrEmptyToggleEntries_AreFilteredOut()
+    {
+        const string json = """
+            { "EnvironmentToggles": [null, "SHARPEMU_TRACE", ""] }
+            """;
+
+        var settings = PerGameSettings.NormalizeFromJson(json);
+
+        Assert.NotNull(settings);
+        Assert.Equal(["SHARPEMU_TRACE"], settings.EnvironmentToggles);
+    }
+
+    // A null list means that the global setting should be inherited.
+    [Fact]
+    public void NormalizeFromJson_NullToggleList_StaysNull()
+    {
+        const string json = """{ "EnvironmentToggles": null }""";
+
+        var settings = PerGameSettings.NormalizeFromJson(json);
+
+        Assert.NotNull(settings);
+        Assert.Null(settings.EnvironmentToggles);
+    }
+
+    [Fact]
+    public void NormalizeFromJson_EmptyToggleList_StaysEmpty()
+    {
+        const string json = """{ "EnvironmentToggles": [] }""";
+
+        var settings = PerGameSettings.NormalizeFromJson(json);
+
+        Assert.NotNull(settings);
+        Assert.Empty(Assert.IsType<List<string>>(settings.EnvironmentToggles));
+    }
+
+    [Fact]
+    public void NormalizeFromJson_ValidToggles_ArePreserved()
+    {
+        const string json = """
+            { "EnvironmentToggles": ["SHARPEMU_TRACE", "SHARPEMU_NO_JIT"] }
+            """;
+
+        var settings = PerGameSettings.NormalizeFromJson(json);
+
+        Assert.NotNull(settings);
+        Assert.Equal(["SHARPEMU_TRACE", "SHARPEMU_NO_JIT"], settings.EnvironmentToggles);
+    }
+}