optionally pass auth client to dbus client

lib/dbus.dart

@@ -1,4 +1,5 @@
 export 'src/dbus_address.dart';
+export 'src/dbus_auth_client.dart';
 export 'src/dbus_client.dart';
 export 'src/dbus_introspect.dart';
 export 'src/dbus_method_call.dart';

lib/src/dbus_auth_client.dart

@@ -15,6 +15,7 @@ class DBusAuthClient {
   var _unixFdSupported = false;
   DBusUUID? _uuid;
   String? _errorMessage;
+  final String? _uid;
 
   /// Stream of requests to send to the authentication server.
   Stream<String> get requests => _requestsController.stream;
@@ -35,7 +36,9 @@ class DBusAuthClient {
   String? get errorMessage => _errorMessage;
 
   /// Creates a new authentication client.
-  DBusAuthClient({bool requestUnixFd = true}) : _requestUnixFd = requestUnixFd {
+  DBusAuthClient({bool requestUnixFd = true, String? uid})
+      : _requestUnixFd = requestUnixFd,
+        _uid = uid {
     // On start, end an empty byte, as this is required if sending the credentials as a socket control message.
     // We rely on the server using SO_PEERCRED to check out credentials.
     // Then request the supported mechanisms.
@@ -126,7 +129,9 @@ class DBusAuthClient {
   /// Start authentication using the EXTERNAL mechanism.
   void _authenticateExternal() {
     String authId;
-    if (Platform.isLinux) {
+    if (_uid != null) {
+      authId = _uid!;
+    } else if (Platform.isLinux) {
       authId = getuid().toString();
     } else if (Platform.isWindows) {
       authId = getsid();

lib/src/dbus_client.dart

@@ -214,7 +214,7 @@ class DBusClient {
   RawSocket? _socket;
   var _socketClosed = false;
   final _readBuffer = DBusReadBuffer();
-  final _authClient = DBusAuthClient();
+  final DBusAuthClient _authClient;
   var _authComplete = false;
   Completer? _connectCompleter;
   var _lastSerial = 0;
@@ -243,11 +243,15 @@ class DBusClient {
 
   /// Creates a new DBus client to connect on [address].
   /// If [messageBus] is false, then the server is not running a message bus and
-  /// no adresses or client to client communication is suported.
+  /// no addresses or client to client communication is supported.
+  /// If [authClient] is provided, it will be used instead of creating a new one.
   DBusClient(DBusAddress address,
-      {this.introspectable = true, bool messageBus = true})
+      {this.introspectable = true,
+      bool messageBus = true,
+      DBusAuthClient? authClient})
       : _address = address,
-        _messageBus = messageBus;
+        _messageBus = messageBus,
+        _authClient = authClient ?? DBusAuthClient();
 
   /// Creates a new DBus client to communicate with the system bus.
   factory DBusClient.system({bool introspectable = true}) {