CmdPal: Extension list search (#41453)

## Summary of the Pull Request

Adds a rough implementation that appears to work, but it hasn’t been
tested. Don’t rely on it yet—I’m too tired to test properly or write a
polished commit message.

Pictures? Pictures!

<img width="2720" height="1624" alt="image"
src="https://github.com/user-attachments/assets/4f9c3360-8d08-4a34-888f-c6890afd0159"
/>

<img width="2647" height="1558" alt="image"
src="https://github.com/user-attachments/assets/3d6c23bc-f26d-4e31-ae09-d91efd304048"
/>

<img width="2683" height="1536" alt="image"
src="https://github.com/user-attachments/assets/6017b2d4-ccd9-4555-b81f-e2b1f78c48e5"
/>

<img width="577" height="334" alt="image"
src="https://github.com/user-attachments/assets/987fea99-05b2-4d31-b90c-327122daa241"
/>


https://github.com/user-attachments/assets/65a8f8ce-ae09-4272-881d-0b6f56cecfae

<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist

- [x] Closes: #41451
- [x] Closes: #42031
- [x] Closes: #41800
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

---------

Co-authored-by: Niels Laute <niels.laute@live.nl>
Co-authored-by: Michael Jolley <mike@baldbeardedbuilder.com>

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Messages/ReloadFinishedMessage.cs

@@ -0,0 +1,7 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.CmdPal.UI.ViewModels.Messages;
+
+public record ReloadFinishedMessage();

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.Designer.cs

@@ -410,5 +410,23 @@ namespace Microsoft.CmdPal.UI.ViewModels.Properties {
                 return ResourceManager.GetString("builtin_reload_subtitle", resourceCulture);
             }
         }
+        
+        /// <summary>
+        ///   Looks up a localized string similar to {0} extensions found.
+        /// </summary>
+        public static string builtin_settings_extension_n_extensions_found {
+            get {
+                return ResourceManager.GetString("builtin_settings_extension_n_extensions_found", resourceCulture);
+            }
+        }
+        
+        /// <summary>
+        ///   Looks up a localized string similar to {0} extensions installed.
+        /// </summary>
+        public static string builtin_settings_extension_n_extensions_installed {
+            get {
+                return ResourceManager.GetString("builtin_settings_extension_n_extensions_installed", resourceCulture);
+            }
+        }
     }
 }

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.resx

@@ -236,4 +236,10 @@
   <data name="builtin_home_name" xml:space="preserve">
     <value>Home</value>
   </data>
+  <data name="builtin_settings_extension_n_extensions_found" xml:space="preserve">
+    <value>{0} extensions found</value>
+  </data>
+  <data name="builtin_settings_extension_n_extensions_installed" xml:space="preserve">
+    <value>{0} extensions installed</value>
+  </data>
 </root>

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

@@ -0,0 +1,144 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+using System.Globalization;
+using System.Text;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using CommunityToolkit.Mvvm.Messaging;
+
+using Microsoft.CmdPal.Core.ViewModels.Messages;
+using Microsoft.CmdPal.UI.ViewModels.Messages;
+using Microsoft.CommandPalette.Extensions.Toolkit;
+
+namespace Microsoft.CmdPal.UI.ViewModels;
+
+/// <summary>
+/// Provides filtering over the list of provider settings view models.
+/// Intended to be used by the UI to bind a TextBox (SearchText) and an ItemsRepeater (FilteredProviders).
+/// </summary>
+public partial class SettingsExtensionsViewModel : ObservableObject
+{
+    private static readonly CompositeFormat LabelNumberExtensionFound
+        = CompositeFormat.Parse(Properties.Resources.builtin_settings_extension_n_extensions_found!);
+
+    private static readonly CompositeFormat LabelNumberExtensionInstalled
+        = CompositeFormat.Parse(Properties.Resources.builtin_settings_extension_n_extensions_installed!);
+
+    private readonly ObservableCollection<ProviderSettingsViewModel> _source;
+    private readonly TaskScheduler _uiScheduler;
+
+    public ObservableCollection<ProviderSettingsViewModel> FilteredProviders { get; } = [];
+
+    private string _searchText = string.Empty;
+
+    public string SearchText
+    {
+        get => _searchText;
+        set
+        {
+            if (_searchText != value)
+            {
+                _searchText = value;
+                OnPropertyChanged();
+                ApplyFilter();
+            }
+        }
+    }
+
+    public string ItemCounterText
+    {
+        get
+        {
+            var hasQuery = !string.IsNullOrWhiteSpace(_searchText);
+            var count = hasQuery ? FilteredProviders.Count : _source.Count;
+            var format = hasQuery ? LabelNumberExtensionFound : LabelNumberExtensionInstalled;
+            return string.Format(CultureInfo.CurrentCulture, format, count);
+        }
+    }
+
+    public bool ShowManualReloadOverlay
+    {
+        get;
+        private set
+        {
+            if (field != value)
+            {
+                field = value;
+                OnPropertyChanged();
+            }
+        }
+    }
+
+    public bool ShowNoResultsPanel => !string.IsNullOrWhiteSpace(_searchText) && FilteredProviders.Count == 0;
+
+    public bool HasResults => !ShowNoResultsPanel;
+
+    public IRelayCommand ReloadExtensionsCommand { get; }
+
+    public SettingsExtensionsViewModel(ObservableCollection<ProviderSettingsViewModel> source, TaskScheduler uiScheduler)
+    {
+        _source = source;
+        _uiScheduler = uiScheduler;
+        _source.CollectionChanged += Source_CollectionChanged;
+        ApplyFilter();
+
+        ReloadExtensionsCommand = new RelayCommand(ReloadExtensions);
+
+        WeakReferenceMessenger.Default.Register<ReloadFinishedMessage>(this, (_, _) =>
+        {
+            Task.Factory.StartNew(() => ShowManualReloadOverlay = false, CancellationToken.None, TaskCreationOptions.None, _uiScheduler);
+        });
+    }
+
+    private void Source_CollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
+    {
+        ApplyFilter();
+    }
+
+    private void ApplyFilter()
+    {
+        var query = _searchText;
+        var filtered = ListHelpers.FilterList(_source, query, Matches);
+        ListHelpers.InPlaceUpdateList(FilteredProviders, filtered);
+        OnPropertyChanged(nameof(ItemCounterText));
+        OnPropertyChanged(nameof(HasResults));
+        OnPropertyChanged(nameof(ShowNoResultsPanel));
+    }
+
+    private static int Matches(string query, ProviderSettingsViewModel item)
+    {
+        if (string.IsNullOrWhiteSpace(query))
+        {
+            return 100;
+        }
+
+        return Contains(item.DisplayName, query)
+               || Contains(item.ExtensionName, query)
+               || Contains(item.ExtensionSubtext, query)
+            ? 100
+            : 0;
+    }
+
+    private static bool Contains(string? haystack, string needle)
+    {
+        return !string.IsNullOrEmpty(haystack) && haystack.Contains(needle, StringComparison.OrdinalIgnoreCase);
+    }
+
+    [RelayCommand]
+    private void OpenStoreWithExtension(string? query)
+    {
+        const string extensionsAssocUri = "ms-windows-store://assoc/?Tags=AppExtension-com.microsoft.commandpalette";
+        ShellHelpers.OpenInShell(extensionsAssocUri);
+    }
+
+    private void ReloadExtensions()
+    {
+        ShowManualReloadOverlay = true;
+        WeakReferenceMessenger.Default.Send<ClearSearchMessage>();
+        WeakReferenceMessenger.Default.Send<ReloadCommandsMessage>();
+    }
+}

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

@@ -140,6 +140,8 @@ public partial class SettingsViewModel : INotifyPropertyChanged
 
     public ObservableCollection<ProviderSettingsViewModel> CommandProviders { get; } = [];
 
+    public SettingsExtensionsViewModel Extensions { get; }
+
     public SettingsViewModel(SettingsModel settings, IServiceProvider serviceProvider, TaskScheduler scheduler)
     {
         _settings = settings;
@@ -155,6 +157,8 @@ public partial class SettingsViewModel : INotifyPropertyChanged
             var settingsModel = new ProviderSettingsViewModel(item, providerSettings, _serviceProvider);
             CommandProviders.Add(settingsModel);
         }
+
+        Extensions = new SettingsExtensionsViewModel(CommandProviders, scheduler);
     }
 
     private IEnumerable<CommandProviderWrapper> GetCommandProviders()

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

@@ -259,6 +259,9 @@ public partial class TopLevelCommandManager : ObservableObject,
 
         IsLoading = false;
 
+        // Send on the current thread; receivers should marshal to UI if needed
+        WeakReferenceMessenger.Default.Send<ReloadFinishedMessage>();
+
         return true;
     }