Check for workspace/configuration availability before sending request (microsoft#1506)

Author: jakebailey

src/LanguageServer/Impl/LanguageServer.Lifetime.cs

@@ -53,6 +53,10 @@ public async Task Initialized(JToken token, CancellationToken cancellationToken)
         }
 
         private async Task<JToken> GetPythonConfigurationAsync(CancellationToken cancellationToken = default, int? cancelAfterMilli = null) {
+            if (_initParams?.capabilities?.workspace?.configuration != true) {
+                return null;
+            }
+
             try {
                 using (var cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken)) {
                     if (cancelAfterMilli.HasValue) {

src/LanguageServer/Impl/Protocol/Classes.cs

@@ -198,6 +198,11 @@ public struct SymbolKindCapabilities {
 
         public struct ExecuteCommandCapabilities { public bool dynamicRegistration; }
         public ExecuteCommandCapabilities? executeCommand;
+
+        /// <summary>
+        /// Supports the 'workspace/configuration' request.
+        /// </summary>
+        public bool? configuration;
     }
 
     [Serializable]