Handle connection exceptions and add error callback (#126)

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

@@ -21,6 +21,11 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution.Contracts
         /// Summaries of the result sets that were returned with the query
         /// </summary>
         public BatchSummary[] BatchSummaries { get; set; }
+
+        /// <summary>
+        /// Error message, if any
+        /// </summary>
+        public string Message { get; set; }
     }
 
     public class QueryExecuteCompleteEvent

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

@@ -102,6 +102,12 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
         /// <param name="q">The query that completed</param>
         public delegate Task QueryAsyncEventHandler(Query q);
 
+        /// <summary>
+        /// Delegate type for callback when a query connection fails
+        /// </summary>
+        /// <param name="q">The query that completed</param>
+        public delegate Task QueryAsyncErrorEventHandler(string message);
+
         /// <summary>
         /// Callback for when the query has completed successfully
         /// </summary>
@@ -112,6 +118,11 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
         /// </summary>
         public event QueryAsyncEventHandler QueryFailed;
 
+        /// <summary>
+        /// Callback for when the query connection has failed
+        /// </summary>
+        public event QueryAsyncErrorEventHandler QueryConnectionException;
+
         /// <summary>
         /// The batches underneath this query
         /// </summary>
@@ -241,7 +252,19 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
             // TODO: Don't create a new connection every time, see TFS #834978
             using (DbConnection conn = editorConnection.Factory.CreateSqlConnection(connectionString))
             {
-                await conn.OpenAsync();
+                try
+                {
+                    await conn.OpenAsync();
+                }
+                catch(Exception exception)
+                {
+                    this.HasExecuted = true;                 
+                    if (QueryConnectionException != null)
+                    {                        
+                        await QueryConnectionException(exception.Message);
+                    }
+                    return;
+                }
 
                 ReliableSqlConnection sqlConn = conn as ReliableSqlConnection;
                 if (sqlConn != null)

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

@@ -427,8 +427,20 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
                 await requestContext.SendEvent(QueryExecuteCompleteEvent.Type, eventParams);
             };
 
+            Query.QueryAsyncErrorEventHandler errorCallback = async errorMessage =>
+            {
+                // Send back the error message
+                QueryExecuteCompleteParams eventParams = new QueryExecuteCompleteParams
+                {
+                    OwnerUri = executeParams.OwnerUri,
+                    Message = errorMessage              
+                };
+                await requestContext.SendEvent(QueryExecuteCompleteEvent.Type, eventParams);
+            };
+
             query.QueryCompleted += callback;
             query.QueryFailed += callback;
+            query.QueryConnectionException += errorCallback;
 
             // Launch this as an asynchronous task
             query.Execute();