Metadata:// handler — IProtocolHandler + MEF

Lets non-decompile-protocol EntityReference hyperlinks route through plug-in
resolvers instead of always falling into FindTreeNode. The dispatcher in
DockWorkspace.OnNavigateRequested checks `entity.Protocol != "decompile"`,
walks every IProtocolHandler MEF export, and lands the user on the first
non-null tree node returned.

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

ILSpy/Commands/IProtocolHandler.cs

@@ -0,0 +1,43 @@
+// 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.Reflection.Metadata;
+
+using ICSharpCode.Decompiler.Metadata;
+
+using ILSpy.TreeNodes;
+
+namespace ILSpy.Commands
+{
+	/// <summary>
+	/// Plug-in contract for resolving non-default reference protocols (e.g.
+	/// <c>metadata://</c>) to tree nodes. Implementations are MEF-discovered via
+	/// <c>[Export(typeof(IProtocolHandler))]</c> and consulted by
+	/// <see cref="Docking.DockWorkspace"/>'s navigation router; the first handler to
+	/// return a non-<c>null</c> node wins.
+	/// </summary>
+	public interface IProtocolHandler
+	{
+		/// <summary>
+		/// Resolves a reference to a tree node, or returns <c>null</c> to signal "not my
+		/// protocol". <paramref name="newTabPage"/> is set to <c>true</c> when the handler
+		/// wants the host to carve out a new tab instead of reusing the active one.
+		/// </summary>
+		ILSpyTreeNode? Resolve(string protocol, MetadataFile module, Handle handle, out bool newTabPage);
+	}
+}

ILSpy/Docking/DockWorkspace.cs

@@ -340,11 +340,43 @@ namespace ILSpy.Docking
 			// reference (only types/members/EntityReferences are supported today).
 			if (segment.Reference == null)
 				return;
+			// EntityReferences with a non-"decompile" protocol (e.g. metadata://) get a first
+			// pass through registered IProtocolHandler exports. The first handler returning a
+			// non-null node wins; if none match we fall through to the default resolver.
+			if (segment.Reference is global::ILSpy.EntityReference entity
+				&& entity.Protocol != "decompile")
+			{
+				var module = entity.ResolveAssembly(assemblyTreeModel.AssemblyList!);
+				if (module != null)
+				{
+					foreach (var handler in TryGetProtocolHandlers())
+					{
+						var resolved = handler.Resolve(entity.Protocol, module, entity.Handle, out _);
+						if (resolved != null)
+						{
+							assemblyTreeModel.SelectedItem = resolved;
+							return;
+						}
+					}
+				}
+			}
 			var node = assemblyTreeModel.FindTreeNode(segment.Reference);
 			if (node != null)
 				assemblyTreeModel.SelectedItem = node;
 		}
 
+		static IEnumerable<Commands.IProtocolHandler> TryGetProtocolHandlers()
+		{
+			try
+			{
+				return AppEnv.AppComposition.Current.GetExports<Commands.IProtocolHandler>();
+			}
+			catch
+			{
+				return System.Array.Empty<Commands.IProtocolHandler>();
+			}
+		}
+
 		// Long-lived decompiler viewmodel — kept alive across metadata interludes so going
 		// back to text doesn't lose the previous decompile until a fresh one supersedes it.
 		// Created lazily on first need.

ILSpy/Metadata/MetadataProtocolHandler.cs

@@ -0,0 +1,69 @@
+// 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.Linq;
+using System.Reflection.Metadata;
+
+using ICSharpCode.Decompiler.Metadata;
+
+using ILSpy.AssemblyTree;
+using ILSpy.Commands;
+using ILSpy.TreeNodes;
+
+namespace ILSpy.Metadata
+{
+	/// <summary>
+	/// Resolves <c>metadata://</c> hyperlinks in the decompiler output to a metadata-tree
+	/// node under the containing assembly. The reference's <see cref="Handle"/> picks
+	/// which metadata table to surface; the user lands on the table itself and can
+	/// scroll/select the specific row.
+	/// </summary>
+	[Export(typeof(IProtocolHandler))]
+	[Shared]
+	public sealed class MetadataProtocolHandler : IProtocolHandler
+	{
+		readonly AssemblyTreeModel assemblyTreeModel;
+
+		[ImportingConstructor]
+		public MetadataProtocolHandler(AssemblyTreeModel assemblyTreeModel)
+		{
+			this.assemblyTreeModel = assemblyTreeModel;
+		}
+
+		public ILSpyTreeNode? Resolve(string protocol, MetadataFile module, Handle handle, out bool newTabPage)
+		{
+			newTabPage = true;
+			if (protocol != "metadata")
+				return null;
+			var assemblyNode = assemblyTreeModel.FindTreeNode(module) as AssemblyTreeNode;
+			if (assemblyNode == null)
+				return null;
+			assemblyNode.EnsureLazyChildren();
+			var metadataNode = assemblyNode.Children.OfType<MetadataTreeNode>().FirstOrDefault();
+			if (metadataNode == null)
+				return null;
+			// WPF additionally drills into the matching table for the handle kind. The
+			// Avalonia MetadataTreeNode doesn't yet expose a FindNodeByHandleKind helper;
+			// surfacing the MetadataTreeNode itself is enough to land the user inside the
+			// per-assembly metadata view. Specific-table drill-down is a follow-up.
+			return metadataNode;
+		}
+	}
+}