Batch Start Notification (#169)

This change is part of the progressive results code. It will submit a notification from the service layer to indicate when execution of a batch has completed. This notification will contain the selection for batch, execution start time, and its ID. This will enable the extension to produce a header for the batch before the batch completes, in order to make it more clear to the user that execution is going on.

* Adding new event for batch start

* Unit tests

* Fixing comments as per @kevcunnane

src/Microsoft.SqlTools.ServiceLayer/QueryExecution/Batch.cs

@@ -75,7 +75,7 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
             this.outputFileFactory = outputFileFactory;
         }
 
-        #region Properties
+        #region Events
 
         /// <summary>
         /// Asynchronous handler for when batches are completed
@@ -88,12 +88,21 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
         /// </summary>
         public event BatchAsyncEventHandler BatchCompletion;
 
+        /// <summary>
+        /// Event to call when the batch has started execution
+        /// </summary>
+        public event BatchAsyncEventHandler BatchStart;
+
         /// <summary>
         /// Event that will be called when the resultset has completed execution. It will not be
         /// called from the Batch but from the ResultSet instance
         /// </summary>
         public event ResultSet.ResultSetAsyncEventHandler ResultSetCompletion;
 
+        #endregion
+
+        #region Properties
+
         /// <summary>
         /// The text of batch that will be executed
         /// </summary>
@@ -175,17 +184,25 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
         {
             get
             {
-                return new BatchSummary
+                // Batch summary with information available at start
+                BatchSummary summary = new BatchSummary
                 {
                     HasError = HasError,
                     Id = Id,
-                    ResultSetSummaries = ResultSummaries,
-                    Messages = ResultMessages.ToArray(),
                     Selection = Selection,
-                    ExecutionElapsed = ExecutionElapsedTime,
-                    ExecutionStart = ExecutionStartTimeStamp,
-                    ExecutionEnd = ExecutionEndTimeStamp
+                    ExecutionStart = ExecutionStartTimeStamp
                 };
+
+                // Add on extra details if we finished executing it
+                if (HasExecuted)
+                {
+                    summary.ResultSetSummaries = ResultSummaries;
+                    summary.Messages = ResultMessages.ToArray();
+                    summary.ExecutionEnd = ExecutionEndTimeStamp;
+                    summary.ExecutionElapsed = ExecutionElapsedTime;
+                }
+
+                return summary;
             }
         }
 
@@ -211,6 +228,12 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
                 throw new InvalidOperationException("Batch has already executed.");
             }
 
+            // Notify that we've started execution
+            if (BatchStart != null)
+            {
+                await BatchStart(this);
+            }
+
             try
             {
                 // Register the message listener to *this instance* of the batch

src/Microsoft.SqlTools.ServiceLayer/QueryExecution/Contracts/QueryExecuteBatchNotifications.cs

@@ -10,7 +10,7 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution.Contracts
     /// Parameters to be sent back as part of a QueryExecuteBatchCompleteEvent to indicate that a
     /// batch of a query completed.
     /// </summary>
-    public class QueryExecuteBatchCompleteParams
+    public class QueryExecuteBatchNotificationParams
     {
         /// <summary>
         /// Summary of the batch that just completed
@@ -26,7 +26,14 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution.Contracts
     public class QueryExecuteBatchCompleteEvent
     {
         public static readonly 
-            EventType<QueryExecuteBatchCompleteParams> Type =
-            EventType<QueryExecuteBatchCompleteParams>.Create("query/batchComplete");
+            EventType<QueryExecuteBatchNotificationParams> Type =
+            EventType<QueryExecuteBatchNotificationParams>.Create("query/batchComplete");
+    }
+
+    public class QueryExecuteBatchStartEvent
+    {
+        public static readonly
+            EventType<QueryExecuteBatchNotificationParams> Type =
+            EventType<QueryExecuteBatchNotificationParams>.Create("query/batchStart");
     }
 }

src/Microsoft.SqlTools.ServiceLayer/QueryExecution/Query.cs

@@ -99,10 +99,15 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
         /// </summary>
         public event Batch.BatchAsyncEventHandler BatchCompleted;
 
+        /// <summary>
+        /// Event to be called when a batch starts execution.
+        /// </summary>
+        public event Batch.BatchAsyncEventHandler BatchStarted;
+
         /// <summary>
         /// Delegate type for callback when a query connection fails
         /// </summary>
-        /// <param name="q">The query that completed</param>
+        /// <param name="message">Error message for the failing query</param>
         public delegate Task QueryAsyncErrorEventHandler(string message);
 
         /// <summary>
@@ -277,6 +282,7 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
                     // We need these to execute synchronously, otherwise the user will be very unhappy
                     foreach (Batch b in Batches)
                     {
+                        b.BatchStart += BatchStarted;
                         b.BatchCompletion += BatchCompleted;
                         b.ResultSetCompletion += ResultSetCompleted;
                         await b.Execute(conn, cancellationSource.Token);

src/Microsoft.SqlTools.ServiceLayer/QueryExecution/QueryExecutionService.cs

@@ -443,17 +443,28 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
             query.QueryFailed += callback;
             query.QueryConnectionException += errorCallback;
 
-            // Setup the batch completion callback
-            Batch.BatchAsyncEventHandler batchCallback = async b =>
+            // Setup the batch callbacks
+            Batch.BatchAsyncEventHandler batchStartCallback = async b =>
             {
-                QueryExecuteBatchCompleteParams eventParams = new QueryExecuteBatchCompleteParams
+                QueryExecuteBatchNotificationParams eventParams = new QueryExecuteBatchNotificationParams
+                {
+                    BatchSummary = b.Summary,
+                    OwnerUri = executeParams.OwnerUri
+                };
+                await requestContext.SendEvent(QueryExecuteBatchStartEvent.Type, eventParams);
+            };
+            query.BatchStarted += batchStartCallback;
+
+            Batch.BatchAsyncEventHandler batchCompleteCallback = async b =>
+            {
+                QueryExecuteBatchNotificationParams eventParams = new QueryExecuteBatchNotificationParams
                 {
                     BatchSummary = b.Summary,
                     OwnerUri = executeParams.OwnerUri
                 };
                 await requestContext.SendEvent(QueryExecuteBatchCompleteEvent.Type, eventParams);
             };
-            query.BatchCompleted += batchCallback;
+            query.BatchCompleted += batchCompleteCallback;
 
             // Setup the ResultSet completion callback
             ResultSet.ResultSetAsyncEventHandler resultCallback = async r =>