Create Diagram context-menu entry — HTML class diagrammer

Right-click an assembly tree node → Create Diagram. Prompts for an output
folder via the new FilePickers.PickFolderAsync helper, then runs the shared
ICSharpCode.ILSpyX.MermaidDiagrammer.GenerateHtmlDiagrammer engine on a
background thread under DockWorkspace.RunWithCancellation (the new wait UI
with a custom "Creating diagram…" title). On completion, pushes a report
into the active tab via ShowText — elapsed time, learn-more link, and an
"Open Explorer" button that selects the generated index.html in the OS file
manager (xdg-open / open -R / explorer.exe per platform).

Assisted-by: Claude:claude-opus-4-7:Claude Code

ILSpy.Tests/ContextMenus/CreateDiagramContextMenuTests.cs

@@ -0,0 +1,95 @@
+// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System.Linq;
+using System.Threading.Tasks;
+
+using Avalonia.Headless.NUnit;
+
+using AwesomeAssertions;
+
+using ICSharpCode.ILSpyX.TreeView;
+
+using ILSpy;
+using ILSpy.AppEnv;
+using ILSpy.Commands;
+using ILSpy.TreeNodes;
+using ILSpy.ViewModels;
+using ILSpy.Views;
+
+using NUnit.Framework;
+
+namespace ICSharpCode.ILSpy.Tests;
+
+[TestFixture]
+public class CreateDiagramContextMenuTests
+{
+	[AvaloniaTest]
+	public async Task Entry_Is_Visible_For_A_Single_Loaded_Assembly()
+	{
+		// The "Create Diagram" context-menu entry must surface when the user right-clicks
+		// exactly one assembly tree node whose underlying file loaded as a valid assembly.
+		// Multi-select, child-node selection, and failed-load nodes should all hide it —
+		// the diagrammer needs a single concrete assembly path to feed to GenerateHtmlDiagrammer.
+		var window = AppComposition.Current.GetExport<MainWindow>();
+		window.Show();
+		var vm = (MainWindowViewModel)window.DataContext!;
+		await vm.AssemblyTreeModel.WaitForAssembliesAsync(minimumCount: 1);
+
+		var entry = AppComposition.Current.GetExport<ContextMenuEntryRegistry>().Entries
+			.Select(e => e.Value).OfType<CreateDiagramContextMenuEntry>().Single();
+
+		var assemblyNode = vm.AssemblyTreeModel.Root!.Children.OfType<AssemblyTreeNode>().First();
+		entry.IsVisible(new TextViewContext { SelectedTreeNodes = new SharpTreeNode[] { assemblyNode } }).Should().BeTrue();
+	}
+
+	[AvaloniaTest]
+	public async Task Entry_Is_Hidden_For_Non_Assembly_Selections()
+	{
+		// Anything that isn't an AssemblyTreeNode (e.g. a TypeTreeNode under it) doesn't
+		// expose the entry — the diagrammer operates on whole-assembly granularity.
+		var window = AppComposition.Current.GetExport<MainWindow>();
+		window.Show();
+		var vm = (MainWindowViewModel)window.DataContext!;
+		await vm.AssemblyTreeModel.WaitForAssembliesAsync(minimumCount: 1);
+
+		var entry = AppComposition.Current.GetExport<ContextMenuEntryRegistry>().Entries
+			.Select(e => e.Value).OfType<CreateDiagramContextMenuEntry>().Single();
+
+		var coreLibName = typeof(object).Assembly.GetName().Name!;
+		var typeNode = vm.AssemblyTreeModel.FindNode<TypeTreeNode>(coreLibName, "System", "System.Object");
+		entry.IsVisible(new TextViewContext { SelectedTreeNodes = new SharpTreeNode[] { typeNode } }).Should().BeFalse();
+	}
+
+	[AvaloniaTest]
+	public async Task Entry_Is_Hidden_For_Multi_Select()
+	{
+		// Multi-select must also hide the entry — the diagrammer runs on one assembly at
+		// a time. (The WPF version uses the same `Length == 1` guard.)
+		var window = AppComposition.Current.GetExport<MainWindow>();
+		window.Show();
+		var vm = (MainWindowViewModel)window.DataContext!;
+		await vm.AssemblyTreeModel.WaitForAssembliesAsync(minimumCount: 1);
+
+		var entry = AppComposition.Current.GetExport<ContextMenuEntryRegistry>().Entries
+			.Select(e => e.Value).OfType<CreateDiagramContextMenuEntry>().Single();
+
+		var assemblyNode = vm.AssemblyTreeModel.Root!.Children.OfType<AssemblyTreeNode>().First();
+		entry.IsVisible(new TextViewContext { SelectedTreeNodes = new SharpTreeNode[] { assemblyNode, assemblyNode } }).Should().BeFalse();
+	}
+}

ILSpy/Commands/CreateDiagramContextMenuEntry.cs

@@ -0,0 +1,140 @@
+// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System;
+using System.Composition;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+
+using ICSharpCode.ILSpy.Properties;
+using ICSharpCode.ILSpyX.MermaidDiagrammer;
+using ICSharpCode.ILSpyX.TreeView;
+
+using ILSpy.Docking;
+using ILSpy.TextView;
+using ILSpy.TreeNodes;
+
+namespace ILSpy.Commands
+{
+	/// <summary>
+	/// Right-click an assembly → "Create Diagram". Asks for an output folder, invokes the
+	/// shared <see cref="GenerateHtmlDiagrammer"/> engine on a background thread, then
+	/// pushes a completion report (elapsed time, learn-more link, Open-Explorer button)
+	/// into the active decompiler tab via <see cref="DockWorkspace.ShowText"/>. Visible
+	/// only when exactly one valid loaded assembly is selected.
+	/// </summary>
+	[ExportContextMenuEntry(Header = nameof(Resources._CreateDiagram), Category = nameof(Resources.Save), Icon = "Images/Save")]
+	[Shared]
+	public sealed class CreateDiagramContextMenuEntry : IContextMenuEntry
+	{
+		readonly DockWorkspace dockWorkspace;
+
+		[ImportingConstructor]
+		public CreateDiagramContextMenuEntry(DockWorkspace dockWorkspace)
+		{
+			this.dockWorkspace = dockWorkspace;
+		}
+
+		public bool IsVisible(TextViewContext context)
+		{
+			return context.SelectedTreeNodes?.Length == 1
+				&& context.SelectedTreeNodes[0] is AssemblyTreeNode tn
+				&& tn.LoadedAssembly.IsLoadedAsValidAssembly;
+		}
+
+		public bool IsEnabled(TextViewContext context) => true;
+
+		public void Execute(TextViewContext context)
+		{
+			var assembly = (context.SelectedTreeNodes?.FirstOrDefault() as AssemblyTreeNode)?.LoadedAssembly;
+			if (assembly == null)
+				return;
+			_ = ExecuteAsync(assembly.FileName);
+		}
+
+		async Task ExecuteAsync(string assemblyFile)
+		{
+			var outputFolder = await FilePickers.PickFolderAsync("Select target folder");
+			if (string.IsNullOrEmpty(outputFolder))
+				return;
+
+			try
+			{
+				var output = await dockWorkspace.RunWithCancellation(
+					token => Task.Run(() => RunGenerator(assemblyFile, outputFolder), token),
+					Resources.CreatingDiagram);
+				dockWorkspace.ShowText(output);
+			}
+			catch (OperationCanceledException)
+			{
+				// User cancelled — leave the previous tab content visible.
+			}
+		}
+
+		static AvaloniaEditTextOutput RunGenerator(string assemblyFile, string outputFolder)
+		{
+			var output = new AvaloniaEditTextOutput();
+			var stopwatch = Stopwatch.StartNew();
+			var command = new GenerateHtmlDiagrammer {
+				Assembly = assemblyFile,
+				OutputFolder = outputFolder,
+			};
+			command.Run();
+			stopwatch.Stop();
+			output.Title = "Create Diagram";
+			output.Write(string.Format(Resources.GenerationCompleteInSeconds, stopwatch.Elapsed.TotalSeconds.ToString("F1")));
+			output.WriteLine();
+			output.WriteLine();
+			output.Write("Learn more: https://github.com/icsharpcode/ILSpy/wiki/Diagramming#tips-for-using-the-html-diagrammer");
+			output.WriteLine();
+			output.WriteLine();
+			var diagramHtml = Path.Combine(outputFolder, "index.html");
+			output.AddButton(null, Resources.OpenExplorer, (_, _) => OpenInShell(diagramHtml));
+			output.WriteLine();
+			return output;
+		}
+
+		static void OpenInShell(string path)
+		{
+			try
+			{
+				if (OperatingSystem.IsWindows())
+				{
+					Process.Start(new ProcessStartInfo("explorer.exe", $"/select,\"{path}\"") { UseShellExecute = false });
+				}
+				else if (OperatingSystem.IsMacOS())
+				{
+					Process.Start(new ProcessStartInfo("open", $"-R \"{path}\"") { UseShellExecute = false });
+				}
+				else
+				{
+					// Linux: no universal "select item" command; open the parent directory instead.
+					var parent = Path.GetDirectoryName(path);
+					if (!string.IsNullOrEmpty(parent))
+						Process.Start(new ProcessStartInfo("xdg-open", parent) { UseShellExecute = false });
+				}
+			}
+			catch
+			{
+				// Best-effort: the user can navigate to the folder manually if the shell call fails.
+			}
+		}
+	}
+}

ILSpy/Commands/FilePickers.cs

@@ -63,6 +63,28 @@ namespace ILSpy.Commands
 			return file?.TryGetLocalPath();
 		}
 
+		/// <summary>
+		/// Shows a folder-picker dialog. <paramref name="title"/> appears in the dialog
+		/// chrome. Returns the selected folder's absolute path, or <c>null</c> if the user
+		/// cancelled or the storage provider refused to give a local path (e.g. cloud
+		/// folder).
+		/// </summary>
+		public static async Task<string?> PickFolderAsync(string? title = null)
+		{
+			var owner = (global::Avalonia.Application.Current?.ApplicationLifetime
+				as IClassicDesktopStyleApplicationLifetime)?.MainWindow;
+			if (owner == null)
+				return null;
+
+			var folders = await owner.StorageProvider.OpenFolderPickerAsync(new FolderPickerOpenOptions {
+				Title = title,
+				AllowMultiple = false,
+			});
+			if (folders.Count == 0)
+				return null;
+			return folders[0].TryGetLocalPath();
+		}
+
 		/// <summary>"PNG (*.png)|*.png|All files|*.*" → two file types.</summary>
 		internal static IReadOnlyList<FilePickerFileType> ParseFilter(string filter)
 		{