Workaround

src/Features/Core/Portable/ExternalAccess/VSTypeScript/VSTypeScriptCommentSelectionService.cs

@@ -12,26 +12,39 @@
 using Microsoft.CodeAnalysis.Formatting;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.Text;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.ExternalAccess.VSTypeScript
 {
     [ExportLanguageService(typeof(ICommentSelectionService), InternalLanguageNames.TypeScript), Shared]
     internal sealed class VSTypeScriptCommentSelectionService : ICommentSelectionService
     {
-        private readonly IVSTypeScriptCommentSelectionServiceImplementation _impl;
+        private readonly IVSTypeScriptCommentSelectionServiceImplementation? _impl;
 
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-        public VSTypeScriptCommentSelectionService(IVSTypeScriptCommentSelectionServiceImplementation impl)
-            => _impl = impl;
+        public VSTypeScriptCommentSelectionService(
+            // Optional to work around test issue: https://github.com/dotnet/roslyn/issues/60690
+            [Import(AllowDefault = true)] IVSTypeScriptCommentSelectionServiceImplementation? impl)
+        {
+            _impl = impl;
+        }
 
         public async Task<CommentSelectionInfo> GetInfoAsync(Document document, TextSpan textSpan, CancellationToken cancellationToken)
         {
+            // Will never be null in product.
+            Contract.ThrowIfNull(_impl);
+
             var info = await _impl.GetInfoAsync(document, textSpan, cancellationToken).ConfigureAwait(false);
             return info.UnderlyingObject;
         }
 
         public Task<Document> FormatAsync(Document document, ImmutableArray<TextSpan> changes, SyntaxFormattingOptions formattingOptions, CancellationToken cancellationToken)
-            => _impl.FormatAsync(document, changes, cancellationToken);
+        {
+            // Will never be null in product.
+            Contract.ThrowIfNull(_impl);
+
+            return _impl.FormatAsync(document, changes, cancellationToken);
+        }
     }
 }