Dump every assembly when decompiling the list root

The list-root node had no Decompile override, so selecting it produced
empty output. Restore the behaviour of emitting a "// List:" header and
each contained assembly under a comment rule.

Assisted-by: Claude:claude-opus-4-8:Claude Code

ILSpy.Tests/AssemblyList/AssemblyListDecompileTests.cs

@@ -0,0 +1,73 @@
+// 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.Threading;
+using System.Threading.Tasks;
+
+using Avalonia.Headless.NUnit;
+
+using AwesomeAssertions;
+
+using ICSharpCode.Decompiler;
+
+using ILSpy;
+using ILSpy.AppEnv;
+using ILSpy.Languages;
+using ILSpy.TreeNodes;
+
+using NUnit.Framework;
+
+namespace ICSharpCode.ILSpy.Tests;
+
+/// <summary>
+/// Decompiling the list root dumps a <c>// List:</c> header and then every assembly in the list,
+/// each under a comment rule. (Regression: the Avalonia port dropped the
+/// <c>AssemblyListTreeNode.Decompile</c> override, so the list root produced no output.)
+/// </summary>
+[TestFixture]
+public class AssemblyListDecompileTests
+{
+	[AvaloniaTest]
+	public async Task Decompiling_The_List_Root_Emits_The_List_Header_And_A_Rule_Per_Assembly()
+	{
+		var (_, vm) = await TestHarness.BootAsync(3);
+		var root = (AssemblyListTreeNode)vm.AssemblyTreeModel.Root!;
+		var language = AppComposition.Current.GetExport<LanguageService>().CurrentLanguage;
+
+		var output = new PlainTextOutput();
+		// Decompiling every assembly is far too slow for a test, so cancel up front: the header
+		// and the first rule are written before the first member decompilation observes the token.
+		var options = new DecompilationOptions { CancellationToken = new CancellationToken(true) };
+
+		try
+		{
+			root.Decompile(language, output, options);
+		}
+		catch (OperationCanceledException)
+		{
+			// expected -- the per-assembly decompilation honours the pre-cancelled token.
+		}
+
+		var text = output.ToString();
+		text.Should().Contain("List: " + root.AssemblyList.ListName,
+			"the list root labels its output with the list name");
+		text.Should().Contain(new string('-', 60),
+			"each assembly is introduced by a comment rule");
+	}
+}

ILSpy/TreeNodes/AssemblyListTreeNode.cs

@@ -58,6 +58,19 @@ namespace ILSpy.TreeNodes
 
 		public override object Text => assemblyList.ListName;
 
+		// Decompiling the list root dumps every assembly in the list, each under a comment rule.
+		public override void Decompile(Languages.Language language, ICSharpCode.Decompiler.ITextOutput output, DecompilationOptions options)
+		{
+			language.WriteCommentLine(output, "List: " + assemblyList.ListName);
+			output.WriteLine();
+			foreach (var asm in Children.OfType<AssemblyTreeNode>())
+			{
+				language.WriteCommentLine(output, new string('-', 60));
+				output.WriteLine();
+				asm.Decompile(language, output, options);
+			}
+		}
+
 		public AssemblyTreeNode? FindAssemblyNode(LoadedAssembly asm)
 			=> Children.OfType<AssemblyTreeNode>().FirstOrDefault(n => n.LoadedAssembly == asm);