Fix: Error if "Solution Items" folder already existed

Author: loop8ack

src/ExtensionManager.VisualStudio.Abstractions/Solution/IVSSolutionItem.cs

@@ -1,3 +1,4 @@
+
 namespace ExtensionManager.VisualStudio.Solution;
 
 /// <summary>
@@ -14,4 +15,9 @@ public interface IVSSolutionItem
     /// The absolute file path on disk.
     /// </summary>
     string? FullPath { get; }
+
+    /// <summary>
+    /// Gets the children of this solution item.
+    /// </summary>
+    Task<IReadOnlyList<IVSSolutionItem>> GetChildrenAsync();
 }

src/ExtensionManager.VisualStudio.Shared/Solution/VSSolutionItem.cs

@@ -1,4 +1,10 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
 using CT = Community.VisualStudio.Toolkit;
+using ThreadHelper = Microsoft.VisualStudio.Shell.ThreadHelper;
 
 #nullable enable
 
@@ -14,4 +20,20 @@ internal class VSSolutionItem<TItem> : IVSSolutionItem
 
     protected VSSolutionItem(TItem inner)
         => Inner = inner;
+
+    public async Task<IReadOnlyList<IVSSolutionItem>> GetChildrenAsync()
+    {
+        await ThreadHelper.JoinableTaskFactory.SwitchToMainThreadAsync();
+
+        return Inner.Children
+            .Where(x => x is not null)
+            .Select(x => (IVSSolutionItem)(x switch
+            {
+                CT.Solution solution => new VSSolution(solution),
+                CT.SolutionFolder folder => new VSSolutionFolder(folder),
+                CT.SolutionItem item => new VSSolutionItem<CT.SolutionItem>(item),
+                _ => throw new NotImplementedException($"The solution item of type {x!.GetType()} is not supported"),
+            }))
+            .ToList();
+    }
 }

src/ExtensionManager/Features/Export/ExportSolutionFeature.cs

@@ -23,8 +23,13 @@ protected override async Task ShowExportDialogAsync(IManifest manifest, IExportW
 
     protected override async Task OnManifestWrittenAsync(string filePath)
     {
+        const string folderName = "Solution Items";
+
         var solution = await _solutions.GetCurrentOrThrowAsync();
-        var folder = await solution.AddSolutionFolderAsync("Solution Items");
+        var solutionChildren = await solution.GetChildrenAsync();
+
+        var folder = solutionChildren.SingleOrDefault(x => x.Name == folderName) as IVSSolutionFolder
+            ?? await solution.AddSolutionFolderAsync(folderName);
 
         if (folder is null)
             throw new InvalidOperationException("Could not add solution folder");