Add support for Dedicated Administrator Connection (#466)

* Prototype support for admin connection

* Added test and used correct default for ADMIN connection casing

src/Microsoft.SqlTools.ServiceLayer/Connection/ConnectionService.cs

@@ -29,6 +29,8 @@ namespace Microsoft.SqlTools.ServiceLayer.Connection
     /// </summary>
     public class ConnectionService
     {
+        public const string AdminConnectionPrefix = "ADMIN:";
+
         /// <summary>
         /// Singleton service instance
         /// </summary>
@@ -444,6 +446,12 @@ namespace Microsoft.SqlTools.ServiceLayer.Connection
                 throw new InvalidOperationException(SR.ConnectionServiceDbErrorDefaultNotConnected(ownerUri));
             }
 
+            if(IsDedicatedAdminConnection(connectionInfo.ConnectionDetails))
+            {
+                // Since this is a dedicated connection only 1 is allowed at any time. Return the default connection for use in the requested action
+                return defaultConnection;
+            }
+
             // Try to get the DbConnection
             DbConnection connection;
             if (!connectionInfo.TryGetConnection(connectionType, out connection) && ConnectionType.Default != connectionType)
@@ -842,12 +850,33 @@ namespace Microsoft.SqlTools.ServiceLayer.Connection
                 await requestContext.SendError(ex.ToString());
             }
         }
-                
+
+        /// <summary>
+        /// Checks if a ConnectionDetails object represents a DAC connection
+        /// </summary>
+        /// <param name="connectionDetails"></param>
+        public static bool IsDedicatedAdminConnection(ConnectionDetails connectionDetails)
+        {
+            Validate.IsNotNull(nameof(connectionDetails), connectionDetails);
+            SqlConnectionStringBuilder builder = CreateConnectionStringBuilder(connectionDetails);
+            string serverName = builder.DataSource;
+            return serverName != null && serverName.StartsWith(AdminConnectionPrefix, StringComparison.OrdinalIgnoreCase);
+        }
+        
         /// <summary>
         /// Build a connection string from a connection details instance
         /// </summary>
         /// <param name="connectionDetails"></param>
         public static string BuildConnectionString(ConnectionDetails connectionDetails)
+        {
+            return CreateConnectionStringBuilder(connectionDetails).ToString();
+        }
+
+        /// <summary>
+        /// Build a connection string builder a connection details instance
+        /// </summary>
+        /// <param name="connectionDetails"></param>
+        public static SqlConnectionStringBuilder CreateConnectionStringBuilder(ConnectionDetails connectionDetails)
         {
             SqlConnectionStringBuilder connectionBuilder;
 
@@ -981,7 +1010,7 @@ namespace Microsoft.SqlTools.ServiceLayer.Connection
                 connectionBuilder.TypeSystemVersion = connectionDetails.TypeSystemVersion;
             }
 
-            return connectionBuilder.ToString();
+            return connectionBuilder;
         }
 
         /// <summary>

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

@@ -834,6 +834,11 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
         {
             await Task.Run(() =>
             {
+                if (ConnectionService.IsDedicatedAdminConnection(info.ConnectionDetails))
+                {
+                    // Intellisense cannot be run on these connections as only 1 SqlConnection can be opened on them at a time
+                    return;
+                }
                 ScriptParseInfo scriptInfo = GetScriptParseInfo(info.OwnerUri, createIfNotExists: true);
                 if (Monitor.TryEnter(scriptInfo.BuildingMetadataLock, LanguageService.OnConnectionWaitTimeout))
                 {

test/Microsoft.SqlTools.ServiceLayer.UnitTests/Connection/ConnectionServiceTests.cs

@@ -1210,6 +1210,48 @@ namespace Microsoft.SqlTools.ServiceLayer.UnitTests.Connection
             await Assert.ThrowsAsync<InvalidOperationException>(
                 () => service.GetOrOpenConnection(TestObjects.ScriptUri, ConnectionType.Query));
         }
+        
+        [Fact]
+        public async Task GetOrOpenAdminDefaultConnection()
+        {
+            // Setup: Create a connection service with an empty connection info obj
+            var service = TestObjects.GetTestConnectionService();
+            var connInfo = new ConnectionInfo(null, null, null);
+            service.OwnerToConnectionMap[TestObjects.ScriptUri] = connInfo;
+
+            // If: I ask for a connection on a connection that doesn't have a default connection
+            // Then: An exception should be thrown
+            await Assert.ThrowsAsync<InvalidOperationException>(
+                () => service.GetOrOpenConnection(TestObjects.ScriptUri, ConnectionType.Query));
+        }
+
+        [Fact]
+        public async Task ConnectionWithAdminConnectionEnsuresOnlyOneConnectionCreated()
+        {
+            // If I try to connect using a connection string, it overrides the server name and username for the connection
+            ConnectParams connectionParameters = TestObjects.GetTestConnectionParams();
+            string serverName = "ADMIN:overriddenServerName";
+            string userName = "overriddenUserName";
+            connectionParameters.Connection.ServerName = serverName;
+            connectionParameters.Connection.UserName = userName;
+
+            // Connect
+            ConnectionService service = TestObjects.GetTestConnectionService();
+            var connectionResult = await service.Connect(connectionParameters);
+            
+            // Verify you can get the connection for default
+            DbConnection defaultConn = await service.GetOrOpenConnection(connectionParameters.OwnerUri, ConnectionType.Default);
+            ConnectionInfo connInfo = service.OwnerToConnectionMap[connectionParameters.OwnerUri];
+            Assert.NotNull(defaultConn);
+            Assert.Equal(connInfo.AllConnections.Count, 1);
+
+            // Verify that for the Query, no new connection is created
+            DbConnection queryConn = await service.GetOrOpenConnection(connectionParameters.OwnerUri, ConnectionType.Query);
+            connInfo = service.OwnerToConnectionMap[connectionParameters.OwnerUri];
+            Assert.NotNull(defaultConn);
+            Assert.Equal(connInfo.AllConnections.Count, 1);
+            
+        }
 
         [Fact]
         public async Task ConnectionWithConnectionStringSucceeds()