Nullability

src/Features/LanguageServer/Protocol/Handler/IRequestHandlerMetadata.cs

@@ -16,7 +16,7 @@ internal interface IRequestHandlerMetadata
         /// <summary>
         /// Name of the language for LSP method to handle (optional).
         /// </summary>
-        string LanguageName { get; }
+        string? LanguageName { get; }
 
         /// <summary>
         /// Whether or not handling this method results in changes to the current solution state

src/Features/LanguageServer/Protocol/Handler/RequestExecutionQueue.QueueItem.cs

@@ -16,10 +16,10 @@ internal partial class RequestExecutionQueue
         {
             public Func<RequestContext, Task<bool>> Callback { get; }
             public bool MutatesSolutionState { get; }
-            public string ClientName { get; }
+            public string? ClientName { get; }
             public ClientCapabilities ClientCapabilities { get; }
 
-            public QueueItem(bool mutatesSolutionState, ClientCapabilities clientCapabilities, string clientName, Func<RequestContext, Task<bool>> callback)
+            public QueueItem(bool mutatesSolutionState, ClientCapabilities clientCapabilities, string? clientName, Func<RequestContext, Task<bool>> callback)
             {
                 MutatesSolutionState = mutatesSolutionState;
                 ClientCapabilities = clientCapabilities;

src/Features/LanguageServer/Protocol/Handler/RequestExecutionQueue.cs

@@ -31,7 +31,7 @@ public RequestExecutionQueue(ILspSolutionProvider solutionProvider)
         }
 
         public Task<TResponseType> ExecuteAsync<TRequestType, TResponseType>(bool mutatesSolutionState, IRequestHandler<TRequestType, TResponseType> handler, TRequestType request,
-            ClientCapabilities clientCapabilities, string clientName, CancellationToken cancellationToken) where TRequestType : class
+            ClientCapabilities clientCapabilities, string? clientName, CancellationToken cancellationToken) where TRequestType : class
         {
             var completion = new TaskCompletionSource<TResponseType>();
 
@@ -83,6 +83,8 @@ private async Task ProcessQueueAsync()
                     // Mutating requests block other requests from starting to ensure an up to date snapshot is used.
                     var ranToCompletion = await work.Callback(context).ConfigureAwait(false);
 
+                    // If the handling of the request failed, the exception will bubble back up to the caller, but we
+                    // still need to react to it here by throwing away solution updates
                     if (ranToCompletion)
                     {
                         _lastMutatedSolution = mutatedSolution ?? _lastMutatedSolution;