Fix for : 4045: Cannot cancel a Query. Query runs too long. (And SMO update) (#780)

* Fix for : 4045: Cannot cancel a Query. Query runs too long.
HandleExecuteRequest was returning a task to awaiter - which was getting waited on. changed it to async function to start task in new thread and return nothing to awaiter . Also the cancellation token set by cancel request was getting checked only after making the connection to execute batches. Added an additional check for cancellation token befor the connection has been made.

Fix for 4319: Error showing dbs when using AAD in... 1.5.0-alpha.74
David has already created a new version of SMO nuget with the fix. - incorporating the same (150.18096.0-preview).

* Adding awaitable internal task for tests to run properly

* Adding more cancel tests

test/Microsoft.SqlTools.ServiceLayer.UnitTests/QueryExecution/CancelTests.cs

@@ -4,6 +4,8 @@
 //
 
 using System.Threading.Tasks;
+using Microsoft.SqlTools.ServiceLayer.Connection;
+using Microsoft.SqlTools.ServiceLayer.QueryExecution;
 using Microsoft.SqlTools.ServiceLayer.QueryExecution.Contracts;
 using Microsoft.SqlTools.ServiceLayer.QueryExecution.Contracts.ExecuteRequests;
 using Microsoft.SqlTools.ServiceLayer.SqlContext;
@@ -29,6 +31,7 @@ namespace Microsoft.SqlTools.ServiceLayer.UnitTests.QueryExecution
             var executeRequest = RequestContextMocks.Create<ExecuteRequestResult>(null);
 
             await queryService.HandleExecuteRequest(executeParams, executeRequest.Object);
+            await queryService.WorkTask;
             await queryService.ActiveQueries[Constants.OwnerUri].ExecutionTask;
             queryService.ActiveQueries[Constants.OwnerUri].HasExecuted = false;    // Fake that it hasn't completed execution
 
@@ -42,8 +45,9 @@ namespace Microsoft.SqlTools.ServiceLayer.UnitTests.QueryExecution
             await queryService.HandleCancelRequest(cancelParams, cancelRequest.Object);
 
             // Then:
-            // ... The query should not have been disposed
+            // ... The query should not have been disposed but should have been cancelled
             Assert.Equal(1, queryService.ActiveQueries.Count);
+            Assert.Equal(true, queryService.ActiveQueries[Constants.OwnerUri].HasCancelled);
             cancelRequest.Validate();
         }
 
@@ -58,6 +62,7 @@ namespace Microsoft.SqlTools.ServiceLayer.UnitTests.QueryExecution
             var executeRequest = RequestContextMocks.Create<ExecuteRequestResult>(null);
 
             await queryService.HandleExecuteRequest(executeParams, executeRequest.Object);
+            await queryService.WorkTask;
             await queryService.ActiveQueries[Constants.OwnerUri].ExecutionTask;
 
             // ... And then I request to cancel the query
@@ -71,8 +76,9 @@ namespace Microsoft.SqlTools.ServiceLayer.UnitTests.QueryExecution
             await queryService.HandleCancelRequest(cancelParams, cancelRequest.Object);
 
             // Then:
-            // ... The query should not have been disposed
+            // ... The query should not have been disposed and cancel should not have excecuted
             Assert.NotEmpty(queryService.ActiveQueries);
+            Assert.Equal(false, queryService.ActiveQueries[Constants.OwnerUri].HasCancelled);
             cancelRequest.Validate();
         }
 
@@ -93,5 +99,40 @@ namespace Microsoft.SqlTools.ServiceLayer.UnitTests.QueryExecution
             await queryService.HandleCancelRequest(cancelParams, cancelRequest.Object);
             cancelRequest.Validate();
         }
+
+        [Fact]
+        public async Task CancelQueryBeforeExecutionStartedTest()
+        {
+            // Setup query settings
+            QueryExecutionSettings querySettings = new QueryExecutionSettings
+            {
+                ExecutionPlanOptions = new ExecutionPlanOptions
+                {
+                    IncludeActualExecutionPlanXml = false,
+                    IncludeEstimatedExecutionPlanXml = true
+                }
+            };
+
+            // Create query with a failure callback function
+            ConnectionInfo ci = Common.CreateTestConnectionInfo(null, false, false);
+            ConnectionService.Instance.OwnerToConnectionMap[ci.OwnerUri] = ci;
+            Query query = new Query(Constants.StandardQuery, ci, querySettings, MemoryFileSystem.GetFileStreamFactory());
+
+            string errorMessage = null;
+            Query.QueryAsyncErrorEventHandler failureCallback = async (q, e) =>
+            {
+                errorMessage = "Error Occured";
+            };
+            query.QueryFailed += failureCallback;
+
+            query.Cancel();
+            query.Execute();
+            await query.ExecutionTask;
+
+            // Validate that query has not been executed but cancelled and query failed called function was called
+            Assert.Equal(true, query.HasCancelled);
+            Assert.Equal(false, query.HasExecuted);
+            Assert.Equal("Error Occured", errorMessage);
+        }
     }
 }