Prevent concurrent loading of catalogs (#2316)

tools/SetupFlow/DevHome.SetupFlow/ViewModels/PackageCatalogListViewModel.cs

@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
@@ -17,16 +18,18 @@
 
 namespace DevHome.SetupFlow.ViewModels;
 
-public partial class PackageCatalogListViewModel : ObservableObject
+public partial class PackageCatalogListViewModel : ObservableObject, IDisposable
 {
     private readonly ICatalogDataSourceLoader _catalogDataSourceLoader;
     private readonly IExtensionService _extensionService;
     private readonly PackageCatalogViewModelFactory _packageCatalogViewModelFactory;
     private readonly DispatcherQueue _dispatcher;
+    private readonly SemaphoreSlim _loadCatalogsSemaphore = new(1, 1);
 
     [ObservableProperty]
     [NotifyPropertyChangedFor(nameof(CatalogFullPath))]
     private PackageCatalogViewModel _viewAllCatalog;
+    private bool disposedValue;
 
     public List<string> CatalogFullPath => new()
     {
@@ -61,10 +64,12 @@ public PackageCatalogListViewModel(
     /// </summary>
     private async Task LoadCatalogsAsync()
     {
-        PackageCatalogs.Clear();
-        AddShimmers(_catalogDataSourceLoader.CatalogCount);
+        // Prevent concurrent loading of catalogs
+        await _loadCatalogsSemaphore.WaitAsync();
         try
         {
+            PackageCatalogs.Clear();
+            AddShimmers(_catalogDataSourceLoader.CatalogCount);
             await foreach (var dataSourceCatalogs in _catalogDataSourceLoader.LoadCatalogsAsync())
             {
                 foreach (var catalog in dataSourceCatalogs)
@@ -75,16 +80,20 @@ private async Task LoadCatalogsAsync()
 
                 RemoveShimmers(dataSourceCatalogs.Count);
             }
+
+            // Remove any remaining shimmers:
+            // This can happen if for example a catalog was detected but not
+            // displayed (e.g. catalog with no packages to display)
+            RemoveShimmers(PackageCatalogShimmers.Count);
         }
         catch (Exception e)
         {
             Log.Logger?.ReportError(Log.Component.AppManagement, $"Failed to load catalogs.", e);
         }
-
-        // Remove any remaining shimmers:
-        // This can happen if for example a catalog was detected but not
-        // displayed (e.g. catalog with no packages to display)
-        RemoveShimmers(PackageCatalogShimmers.Count);
+        finally
+        {
+            _loadCatalogsSemaphore.Release();
+        }
     }
 
     /// <summary>
@@ -146,4 +155,23 @@ private async void OnExtensionChangedAsync(object sender, EventArgs e)
     {
         await _dispatcher.EnqueueAsync(() => LoadCatalogsAsync());
     }
+
+    private void Dispose(bool disposing)
+    {
+        if (!disposedValue)
+        {
+            if (disposing)
+            {
+                _loadCatalogsSemaphore.Dispose();
+            }
+
+            disposedValue = true;
+        }
+    }
+
+    public void Dispose()
+    {
+        Dispose(disposing: true);
+        GC.SuppressFinalize(this);
+    }
 }