Add a LiveShare project snapshot base to make it easier to detect breaking changes.

src/Microsoft.CodeAnalysis.Razor.Workspaces/ProjectSystem/LiveShareProjectSnapshotBase.cs

@@ -0,0 +1,36 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.CodeAnalysis.Razor.ProjectSystem;
+
+namespace Microsoft.CodeAnalysis.Razor.Workspaces.ProjectSystem
+{
+    // This is a marker class to allow us to know when potential breaking changes might impact live share.
+    // This is intentionally not abstract so any API changes that happen to ProjectSnapshot will break this.
+    internal class LiveShareProjectSnapshotBase : ProjectSnapshot
+    {
+        public override RazorConfiguration Configuration => throw new NotImplementedException();
+
+        public override IEnumerable<string> DocumentFilePaths => throw new NotImplementedException();
+
+        public override string FilePath => throw new NotImplementedException();
+
+        public override bool IsInitialized => throw new NotImplementedException();
+
+        public override VersionStamp Version => throw new NotImplementedException();
+
+        public override Project WorkspaceProject => throw new NotImplementedException();
+
+        public override DocumentSnapshot GetDocument(string filePath) => throw new NotImplementedException();
+
+        public override RazorProjectEngine GetProjectEngine() => throw new NotImplementedException();
+
+        public override Task<IReadOnlyList<TagHelperDescriptor>> GetTagHelpersAsync() => throw new NotImplementedException();
+
+        public override bool TryGetTagHelpers(out IReadOnlyList<TagHelperDescriptor> result) => throw new NotImplementedException();
+    }
+}