LanguageService must send result or intellisense hangs (#395)

* LanguageService must send result or intellisense hangs
- Unless the language services methods return results for requests, the VSCode language service protocol will never send a response up to its higher-level code. This means with intellisense off, it appears to hang instead of saying "No results found". This is clearly sub-optimal and if any other extension wants to provide SQL suggestions, it would break them from sending results
- Minor refactor to fully remove Instance-field references in the code

src/Microsoft.SqlTools.ServiceLayer/LanguageServices/LanguageService.cs

@@ -73,6 +73,8 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
 
         private WorkspaceService<SqlToolsSettings> workspaceServiceInstance;
 
+        private ServiceHost serviceHostInstance;
+
         private object parseMapLock = new object();
 
         private ScriptParseInfo currentCompletionParseInfo;
@@ -178,6 +180,22 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
             }
         }
 
+        internal ServiceHost ServiceHostInstance
+        {
+            get
+            {
+                if (this.serviceHostInstance == null)
+                {
+                    this.serviceHostInstance = ServiceHost.Instance;
+                }
+                return this.serviceHostInstance;
+            }
+            set
+            {
+                this.serviceHostInstance = value;
+            }
+        }
+
         /// <summary>
         /// Gets the current settings
         /// </summary>
@@ -233,6 +251,8 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
                 await Task.FromResult(0);
             });
 
+            ServiceHostInstance = serviceHost;
+
             // Register the configuration update handler
             WorkspaceServiceInstance.RegisterConfigChangeCallback(HandleDidChangeConfigurationNotification);
 
@@ -270,7 +290,7 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
             // check if Intellisense suggestions are enabled
             if (ShouldSkipIntellisense(textDocumentPosition.TextDocument.Uri))
             {
-                await Task.FromResult(true);
+                await requestContext.SendResult(null);
             }
             else
             {
@@ -283,7 +303,7 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
                     scriptFile.ClientFilePath,
                     out connInfo);
 
-                var completionItems = Instance.GetCompletionItems(
+                var completionItems = GetCompletionItems(
                     textDocumentPosition, scriptFile, connInfo);
 
                    await requestContext.SendResult(completionItems);
@@ -305,7 +325,7 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
             // Note: Do not know file, so no need to check for MSSQL flavor
             if (!CurrentWorkspaceSettings.IsSuggestionsEnabled)
             {
-                await Task.FromResult(true);
+                await requestContext.SendResult(completionItem);
             }
             else
             {
@@ -369,14 +389,14 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
             ReferencesParams referencesParams,
             RequestContext<Location[]> requestContext)
         {
-            await Task.FromResult(true);
+            await requestContext.SendResult(null);
         }
 
         private async Task HandleDocumentHighlightRequest(
             TextDocumentPosition textDocumentPosition,
             RequestContext<DocumentHighlight[]> requestContext)
         {
-            await Task.FromResult(true);
+            await requestContext.SendResult(null);
         }
 #endif
 
@@ -387,7 +407,7 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
             // check if Intellisense suggestions are enabled
             if (ShouldSkipNonMssqlFile(textDocumentPosition))
             {
-                await Task.FromResult(true);
+                await requestContext.SendResult(null);
             }
             else
             {
@@ -528,19 +548,19 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
                         }
 
                         // Send a notification to signal that autocomplete is ready
-                        ServiceHost.Instance.SendEvent(IntelliSenseReadyNotification.Type, new IntelliSenseReadyParams() {OwnerUri = connInfo.OwnerUri});
+                        ServiceHostInstance.SendEvent(IntelliSenseReadyNotification.Type, new IntelliSenseReadyParams() {OwnerUri = connInfo.OwnerUri});
                     });
                 }
                 else
                 {
                     // Send a notification to signal that autocomplete is ready
-                    await ServiceHost.Instance.SendEvent(IntelliSenseReadyNotification.Type, new IntelliSenseReadyParams() {OwnerUri = rebuildParams.OwnerUri});
+                    await ServiceHostInstance.SendEvent(IntelliSenseReadyNotification.Type, new IntelliSenseReadyParams() {OwnerUri = rebuildParams.OwnerUri});
                 }
             }
             catch (Exception ex)
             {
                 Logger.Write(LogLevel.Error, "Unknown error " + ex.ToString());
-                await ServiceHost.Instance.SendEvent(IntelliSenseReadyNotification.Type, new IntelliSenseReadyParams() {OwnerUri = rebuildParams.OwnerUri});
+                await ServiceHostInstance.SendEvent(IntelliSenseReadyNotification.Type, new IntelliSenseReadyParams() {OwnerUri = rebuildParams.OwnerUri});
             }
         }
 
@@ -721,7 +741,7 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
                 PrepopulateCommonMetadata(info, scriptInfo, this.BindingQueue);
 
                 // Send a notification to signal that autocomplete is ready
-                ServiceHost.Instance.SendEvent(IntelliSenseReadyNotification.Type, new IntelliSenseReadyParams() {OwnerUri = info.OwnerUri});
+                ServiceHostInstance.SendEvent(IntelliSenseReadyNotification.Type, new IntelliSenseReadyParams() {OwnerUri = info.OwnerUri});
             });
         }
 

test/Microsoft.SqlTools.ServiceLayer.UnitTests/LanguageServer/AutocompleteTests.cs

@@ -54,27 +54,31 @@ namespace Microsoft.SqlTools.ServiceLayer.UnitTests.LanguageServer
         }
 
         [Fact]
-        public void HandleSignatureHelpRequestNonMssqlFile()
+        public async Task HandleSignatureHelpRequestNonMssqlFile()
         {
             InitializeTestObjects();
 
             // setup the mock for SendResult
             var signatureRequestContext = new Mock<RequestContext<SignatureHelp>>();
+            SignatureHelp result = null;
             signatureRequestContext.Setup(rc => rc.SendResult(It.IsAny<SignatureHelp>()))
-                .Returns(Task.FromResult(0));
+            .Returns<SignatureHelp>((signature) => {
+                result = signature;
+                return Task.FromResult(0);
+            });
             signatureRequestContext.Setup(rc => rc.SendError(It.IsAny<string>(), It.IsAny<int>())).Returns(Task.FromResult(0));
 
 
             langService.CurrentWorkspaceSettings.SqlTools.IntelliSense.EnableIntellisense = true;
-            langService.HandleDidChangeLanguageFlavorNotification(new LanguageFlavorChangeParams {
+            await langService.HandleDidChangeLanguageFlavorNotification(new LanguageFlavorChangeParams {
                 Uri = textDocument.TextDocument.Uri,
                 Language = LanguageService.SQL_LANG.ToLower(),
                 Flavor = "NotMSSQL"
             }, null);
-            Assert.NotNull(langService.HandleSignatureHelpRequest(textDocument, signatureRequestContext.Object));
-            
-            // verify that no events were sent
-            signatureRequestContext.Verify(m => m.SendResult(It.IsAny<SignatureHelp>()), Times.Never());
+            await langService.HandleSignatureHelpRequest(textDocument, signatureRequestContext.Object);
+            // verify that the response was sent with a null response value
+            signatureRequestContext.Verify(m => m.SendResult(It.IsAny<SignatureHelp>()), Times.Once());
+            Assert.Null(result);
             signatureRequestContext.Verify(m => m.SendError(It.IsAny<string>(), It.IsAny<int>()), Times.Never());
         }