Make a bunch of API changes.

lib/src/client.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library oauth2.client;
 
 import 'dart:async';
 
 import 'package:http/http.dart' as http;
 
@@ skipping 51 matching lines @@
   final String secret;
 
   /// The credentials this client uses to prove to the resource server that it's
   /// authorized.
   ///
   /// This may change from request to request as the credentials expire and the
   /// client refreshes them automatically.
   Credentials get credentials => _credentials;
   Credentials _credentials;
 
+  /// Whether to use HTTP Basic authentication for authorizing the client.
+  final bool _basicAuth;
+
   /// The underlying HTTP client.
   http.Client _httpClient;
 
   /// Creates a new client from a pre-existing set of credentials.
   ///
   /// When authorizing a client for the first time, you should use
   /// [AuthorizationCodeGrant] instead of constructing a [Client] directly.
   ///
   /// [httpClient] is the underlying client that this forwards requests to after
   /// adding authorization credentials to them.
-  Client(
-      this.identifier,
-      this.secret,
-      this._credentials,
-      {http.Client httpClient})
-    : _httpClient = httpClient == null ? new http.Client() : httpClient;
+  ///
+  /// Thrwos an [ArgumentError] if [secret] is passed without [identifier].

[Bob Nystrom, 2015/08/26 16:52:44]

"Throws"

[nweiz, 2015/08/26 20:47:28]

Done.

+  Client(this._credentials, {this.identifier, this.secret,
+          bool basicAuth: true, http.Client httpClient})
+      : _basicAuth = basicAuth,
+        _httpClient = httpClient == null ? new http.Client() : httpClient {
+    if (identifier == null && secret != null) {
+      throw new ArgumentError("secret may not be passed without identifier.");
+    }
+  }
 
   /// Sends an HTTP request with OAuth2 authorization credentials attached.
   ///
   /// This will also automatically refresh this client's [Credentials] before
   /// sending the request if necessary.
   Future<http.StreamedResponse> send(http.BaseRequest request) async {
     if (credentials.isExpired) {
       if (!credentials.canRefresh) throw new ExpirationException(credentials);
       await refreshCredentials();
     }
@@ skipping 32 matching lines @@
   /// [newScopes]. These must be a subset of the scopes in the
   /// [Credentials.scopes] field of [Client.credentials].
   Future<Client> refreshCredentials([List<String> newScopes]) async {
     if (!credentials.canRefresh) {
       var prefix = "OAuth credentials";
       if (credentials.isExpired) prefix = "$prefix have expired and";
       throw new StateError("$prefix can't be refreshed.");
     }
 
     _credentials = await credentials.refresh(
-        identifier, secret,
-        newScopes: newScopes, httpClient: _httpClient);
+        identifier: identifier,
+        secret: secret,
+        newScopes: newScopes,
+        basicAuth: _basicAuth,
+        httpClient: _httpClient);
 
     return this;
   }
 
   /// Closes this client and its underlying HTTP client.
   void close() {
     if (_httpClient != null) _httpClient.close();
     _httpClient = null;
   }
 }