CmdPal: Fix settings deserialization ignoring defaults

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/AppStateModel.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Immutable;
+using System.Text.Json.Serialization;
 
 namespace Microsoft.CmdPal.UI.ViewModels;
 
@@ -17,4 +18,17 @@ public record AppStateModel
 
     // END SETTINGS
     ///////////////////////////////////////////////////////////////////////////
+
+    public AppStateModel()
+    {
+    }
+
+    [JsonConstructor]
+    public AppStateModel(
+        RecentCommandsManager recentCommands,
+        ImmutableList<string> runHistory)
+    {
+        RecentCommands = recentCommands ?? new();
+        RunHistory = runHistory ?? ImmutableList<string>.Empty;
+    }
 }

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/ProviderSettings.cs

@@ -38,9 +38,14 @@ public ProviderSettings()
     }
 
     [JsonConstructor]
-    public ProviderSettings(bool isEnabled)
+    public ProviderSettings(
+        ImmutableDictionary<string, FallbackSettings> fallbackCommands,
+        ImmutableList<string> pinnedCommandIds,
+        bool isEnabled = true)
     {
         IsEnabled = isEnabled;
+        FallbackCommands = fallbackCommands ?? ImmutableDictionary<string, FallbackSettings>.Empty;
+        PinnedCommandIds = pinnedCommandIds ?? ImmutableList<string>.Empty;
     }
 
     /// <summary>

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/RecentCommandsManager.cs

@@ -16,6 +16,12 @@ public RecentCommandsManager()
     {
     }
 
+    [JsonConstructor]
+    internal RecentCommandsManager(ImmutableList<HistoryItem> history)
+    {
+        History = history ?? ImmutableList<HistoryItem>.Empty;
+    }
+
     public int GetCommandHistoryWeight(string commandId)
     {
         var entry = History

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Settings/DockSettings.cs

@@ -16,6 +16,35 @@ namespace Microsoft.CmdPal.UI.ViewModels.Settings;
 /// </summary>
 public record DockSettings
 {
+    private static readonly ImmutableList<DockBandSettings> DefaultStartBands = ImmutableList.Create(
+        new DockBandSettings
+        {
+            ProviderId = "com.microsoft.cmdpal.builtin.core",
+            CommandId = "com.microsoft.cmdpal.home",
+        },
+        new DockBandSettings
+        {
+            ProviderId = "WinGet",
+            CommandId = "com.microsoft.cmdpal.winget",
+            ShowLabels = false,
+        });
+
+    private static readonly ImmutableList<DockBandSettings> DefaultEndBands = ImmutableList.Create(
+        new DockBandSettings
+        {
+            ProviderId = "PerformanceMonitor",
+            CommandId = "com.microsoft.cmdpal.performanceWidget",
+        },
+        new DockBandSettings
+        {
+            ProviderId = "com.microsoft.cmdpal.builtin.datetime",
+            CommandId = "com.microsoft.cmdpal.timedate.dockBand",
+        });
+
+    private static readonly Color DefaultCustomThemeColor = new() { A = 0, R = 255, G = 255, B = 255 }; // Transparent — avoids WinUI3 COM dependency on Colors.Transparent and COM in class init
+
+    private readonly Color? _customThemeColor;
+
     public DockSide Side { get; init; } = DockSide.Top;
 
     public DockSize DockSize { get; init; } = DockSize.Small;
@@ -31,7 +60,20 @@ public record DockSettings
 
     public ColorizationMode ColorizationMode { get; init; }
 
-    public Color CustomThemeColor { get; init; } = new() { A = 0, R = 255, G = 255, B = 255 }; // Transparent — avoids WinUI3 COM dependency on Colors.Transparent and COM in class init
+    [JsonPropertyName("CustomThemeColor")]
+    [JsonInclude]
+    internal Color? CustomThemeColorFallback
+    {
+        get => _customThemeColor;
+        init => _customThemeColor = value;
+    }
+
+    [JsonIgnore]
+    public Color CustomThemeColor
+    {
+        get => _customThemeColor ?? DefaultCustomThemeColor;
+        init => _customThemeColor = value;
+    }
 
     public int CustomThemeColorIntensity { get; init; } = 100;
 
@@ -46,32 +88,11 @@ public record DockSettings
     public string? BackgroundImagePath { get; init; }
 
     // </Theme settings>
-    public ImmutableList<DockBandSettings> StartBands { get; init; } = ImmutableList.Create(
-        new DockBandSettings
-        {
-            ProviderId = "com.microsoft.cmdpal.builtin.core",
-            CommandId = "com.microsoft.cmdpal.home",
-        },
-        new DockBandSettings
-        {
-            ProviderId = "WinGet",
-            CommandId = "com.microsoft.cmdpal.winget",
-            ShowLabels = false,
-        });
+    public ImmutableList<DockBandSettings> StartBands { get; init; } = DefaultStartBands;
 
     public ImmutableList<DockBandSettings> CenterBands { get; init; } = ImmutableList<DockBandSettings>.Empty;
 
-    public ImmutableList<DockBandSettings> EndBands { get; init; } = ImmutableList.Create(
-        new DockBandSettings
-        {
-            ProviderId = "PerformanceMonitor",
-            CommandId = "com.microsoft.cmdpal.performanceWidget",
-        },
-        new DockBandSettings
-        {
-            ProviderId = "com.microsoft.cmdpal.builtin.datetime",
-            CommandId = "com.microsoft.cmdpal.timedate.dockBand",
-        });
+    public ImmutableList<DockBandSettings> EndBands { get; init; } = DefaultEndBands;
 
     public bool ShowLabels { get; init; } = true;
 
@@ -80,6 +101,33 @@ public record DockSettings
         StartBands.Select(b => (b.ProviderId, b.CommandId))
         .Concat(CenterBands.Select(b => (b.ProviderId, b.CommandId)))
         .Concat(EndBands.Select(b => (b.ProviderId, b.CommandId)));
+
+    public DockSettings()
+    {
+    }
+
+    [JsonConstructor]
+    public DockSettings(
+        ImmutableList<DockBandSettings> startBands,
+        ImmutableList<DockBandSettings> centerBands,
+        ImmutableList<DockBandSettings> endBands,
+        DockSide side = DockSide.Top,
+        bool alwaysOnTop = true,
+        DockBackdrop backdrop = DockBackdrop.Acrylic,
+        int customThemeColorIntensity = 100,
+        int backgroundImageOpacity = 20,
+        bool showLabels = true)
+    {
+        StartBands = startBands ?? DefaultStartBands;
+        CenterBands = centerBands ?? ImmutableList<DockBandSettings>.Empty;
+        EndBands = endBands ?? DefaultEndBands;
+        Side = side;
+        AlwaysOnTop = alwaysOnTop;
+        Backdrop = backdrop;
+        CustomThemeColorIntensity = customThemeColorIntensity;
+        BackgroundImageOpacity = backgroundImageOpacity;
+        ShowLabels = showLabels;
+    }
 }
 
 /// <summary>

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/SettingsModel.cs

@@ -15,6 +15,8 @@ public record SettingsModel
     // SETTINGS HERE
     public static HotkeySettings DefaultActivationShortcut { get; } = new HotkeySettings(true, false, true, false, 0x20); // win+alt+space
 
+    private static readonly Color DefaultCustomThemeColor = new() { A = 0, R = 255, G = 255, B = 255 }; // Transparent — avoids WinUI3 COM dependency on Colors.Transparent
+
     public HotkeySettings? Hotkey { get; init; } = DefaultActivationShortcut;
 
     public bool UseLowLevelGlobalHotkey { get; init; }
@@ -56,7 +58,22 @@ public record SettingsModel
 
     public WindowPosition? LastWindowPosition { get; init; }
 
-    public TimeSpan AutoGoHomeInterval { get; init; } = Timeout.InfiniteTimeSpan;
+    [JsonPropertyName("AutoGoHomeInterval")]
+    [JsonInclude]
+    internal string? AutoGoHomeIntervalString
+    {
+        get => _autoGoHomeInterval?.ToString();
+        init => _autoGoHomeInterval = TimeSpan.TryParse(value, out var ts) ? ts : null;
+    }
+
+    private TimeSpan? _autoGoHomeInterval;
+
+    [JsonIgnore]
+    public TimeSpan AutoGoHomeInterval
+    {
+        get => _autoGoHomeInterval ?? Timeout.InfiniteTimeSpan;
+        init => _autoGoHomeInterval = value;
+    }
 
     public EscapeKeyBehavior EscapeKeyBehaviorSetting { get; init; } = EscapeKeyBehavior.ClearSearchFirstThenGoBack;
 
@@ -69,7 +86,22 @@ public record SettingsModel
 
     public ColorizationMode ColorizationMode { get; init; }
 
-    public Color CustomThemeColor { get; init; } = new() { A = 0, R = 255, G = 255, B = 255 }; // Transparent — avoids WinUI3 COM dependency on Colors.Transparent
+    private Color? _customThemeColor;
+
+    [JsonPropertyName("CustomThemeColor")]
+    [JsonInclude]
+    internal Color? CustomThemeColorFallback
+    {
+        get => _customThemeColor;
+        init => _customThemeColor = value;
+    }
+
+    [JsonIgnore]
+    public Color CustomThemeColor
+    {
+        get => _customThemeColor ?? DefaultCustomThemeColor;
+        init => _customThemeColor = value;
+    }
 
     public int CustomThemeColorIntensity { get; init; } = 100;
 
@@ -94,6 +126,39 @@ public record SettingsModel
     // END SETTINGS
     ///////////////////////////////////////////////////////////////////////////
 
+    public SettingsModel()
+    {
+    }
+
+    [JsonConstructor]
+    public SettingsModel(
+        ImmutableDictionary<string, ProviderSettings> providerSettings,
+        string[] fallbackRanks,
+        ImmutableDictionary<string, CommandAlias> aliases,
+        ImmutableList<TopLevelHotkey> commandHotkeys,
+        DockSettings dockSettings,
+        bool highlightSearchOnActivate = true,
+        bool showSystemTrayIcon = true,
+        bool ignoreShortcutWhenFullscreen = true,
+        bool disableAnimations = true,
+        int customThemeColorIntensity = 100,
+        int backgroundImageOpacity = 20,
+        int backdropOpacity = 100)
+    {
+        ProviderSettings = providerSettings ?? ImmutableDictionary<string, ProviderSettings>.Empty;
+        FallbackRanks = fallbackRanks ?? [];
+        Aliases = aliases ?? ImmutableDictionary<string, CommandAlias>.Empty;
+        CommandHotkeys = commandHotkeys ?? ImmutableList<TopLevelHotkey>.Empty;
+        DockSettings = dockSettings ?? new();
+        HighlightSearchOnActivate = highlightSearchOnActivate;
+        ShowSystemTrayIcon = showSystemTrayIcon;
+        IgnoreShortcutWhenFullscreen = ignoreShortcutWhenFullscreen;
+        DisableAnimations = disableAnimations;
+        CustomThemeColorIntensity = customThemeColorIntensity;
+        BackgroundImageOpacity = backgroundImageOpacity;
+        BackdropOpacity = backdropOpacity;
+    }
+
     public (SettingsModel Model, ProviderSettings Settings) GetProviderSettings(CommandProviderWrapper provider)
     {
         if (!ProviderSettings.TryGetValue(provider.ProviderId, out var settings))

src/modules/cmdpal/Tests/Microsoft.CmdPal.UI.ViewModels.UnitTests/SettingsServiceTests.cs

@@ -4,8 +4,13 @@
 
 using System;
 using System.IO;
+using System.Reflection;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using System.Text.Json.Serialization.Metadata;
 using Microsoft.CmdPal.Common.Services;
 using Microsoft.CmdPal.UI.ViewModels.Services;
+using Microsoft.CmdPal.UI.ViewModels.Settings;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Moq;
 
@@ -224,4 +229,76 @@ public void UpdateSettings_ConcurrentUpdates_NoLostUpdates()
         Assert.IsTrue(service.Settings.ShowAppDetails, "ShowAppDetails lost — a stale snapshot overwrote it");
         Assert.IsTrue(service.Settings.SingleClickActivates, "SingleClickActivates lost — a stale snapshot overwrote it");
     }
+
+    /// <summary>
+    /// Verifies that deserializing empty JSON "{}" produces the same non-null
+    /// property values as calling <c>new()</c>. This catches the System.Text.Json
+    /// source-gen issue where property initializers are not honored and reference-type
+    /// properties silently end up null. The test is future-proof: adding a new
+    /// property with a default value to any of these models will automatically be
+    /// covered without touching this test.
+    /// </summary>
+    [TestMethod]
+    public void Deserialize_EmptyJson_MatchesConstructorDefaults()
+    {
+        AssertDeserializedMatchesConstructor(new SettingsModel(), JsonSerializationContext.Default.SettingsModel);
+        AssertDeserializedMatchesConstructor(new AppStateModel(), JsonSerializationContext.Default.AppStateModel);
+        AssertDeserializedMatchesConstructor(new RecentCommandsManager(), JsonSerializationContext.Default.RecentCommandsManager);
+        AssertDeserializedMatchesConstructor(new DockSettings(), JsonSerializationContext.Default.DockSettings);
+        AssertDeserializedMatchesConstructor(new ProviderSettings(), JsonSerializationContext.Default.ProviderSettings);
+    }
+
+    /// <summary>
+    /// Deserializes "{}" into <typeparamref name="T"/> and compares every
+    /// readable instance property against a <c>new()</c> instance. Asserts
+    /// that every non-nullable property has the same value after deserialization
+    /// as it does from the parameterless constructor. This catches the
+    /// System.Text.Json source-gen issue where property initializers are not
+    /// honored — both for reference types (which end up null) and value types
+    /// (which end up as default(T) instead of the intended default).
+    /// </summary>
+    private static void AssertDeserializedMatchesConstructor<T>(T constructed, JsonTypeInfo<T> typeInfo)
+        where T : class
+    {
+        var deserialized = JsonSerializer.Deserialize("{}", typeInfo);
+        Assert.IsNotNull(deserialized, $"Deserialize<{typeof(T).Name}>(\"{{}}\") returned null");
+
+        var nullabilityContext = new NullabilityInfoContext();
+        var typeName = typeof(T).Name;
+        foreach (var prop in typeof(T).GetProperties(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance))
+        {
+            if (!prop.CanRead || prop.GetIndexParameters().Length > 0)
+            {
+                continue;
+            }
+
+            // Skip computed [JsonIgnore] properties (no setter) - they aren't
+            // deserialized and comparing complex return types is unreliable.
+            // Writable [JsonIgnore] properties (e.g. fallback-backed properties)
+            // are still checked since they should match constructor defaults.
+            if (prop.GetCustomAttribute<JsonIgnoreAttribute>() is not null && !prop.CanWrite)
+            {
+                continue;
+            }
+
+            // Skip nullable properties — null is a valid value for them,
+            // so a mismatch with the constructor default is expected.
+            var nullabilityInfo = nullabilityContext.Create(prop);
+            if (nullabilityInfo.WriteState is NullabilityState.Nullable)
+            {
+                continue;
+            }
+
+            var expected = prop.GetValue(constructed);
+            var actual = prop.GetValue(deserialized);
+            var label = $"{typeName}.{prop.Name}";
+
+            if (expected is not null)
+            {
+                Assert.IsNotNull(actual, $"{label} is null after deserialization but non-null from constructor");
+            }
+
+            Assert.AreEqual(expected, actual, $"{label} value mismatch - deserialized default differs from constructor default");
+        }
+    }
 }